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Litter Production in Forests of the World†
Litter Production in Forests of the Worldt
.
J ROGER B R A Y
Grasslands Division. D.S.I.R., Palmerston North. New Zealand and E V I L L E GORHAM
Botany Department. University of Minnesota. Minneapolis. Minn., U .S.A . I. Introduction ........................................................ 101 I1. SourcesofData...................................................... 104 A. UnpublishedStudybyJ.R.Bray ................................... 104 B . WorldReview .................................................... 106 I11. Selection and Presentation of Data ..................................... 107 A Criteriafor Acceptance ............................................ 107 B . Arrangement ..................................................... 108 IV. Litter Components ................................................... 118 A Detailed Litter Separation ......................................... 118 B . Percentage of Non-Leaf Litter ...................................... 118 C Understory Litter ................................................ 119 D MineralMaterial .................................................. 121 E . OrganicMaterial.................................................. 125 V Factors Affecting Litter-Fall .......................................... 125 A. Evergreen Gymnosperm and Deciduous Angiosperms ................. 125 B Environment ..................................................... 127 C. Treatment ....................................................... 131 D . TheTimeFactor ................................................. 133 VI. StandingCropofLeaves.............................................. 142 A SeasonalChanges-Intrinsic ...................................... 142 B . Seasonal Changes - Extrinsic ....................................... 144 C . MagnitudeofLeafCrops ........................................... 144 VII . Leaf Litter as an Index to Net Production ............................... 147 References................................................................ 152
.
. . .
.
. .
I . INTRODUCTION The organic debris shed by forest vegetation upon the surface of the soil has long engaged attention . I n the past. branches and twigs were
t This study formed part of the authors’ research programmes while they were on the staff of the University of Toronto. Canada.
102
J . ROGER BRAY A N D EVILLE GORHAM
used as fuel, and leaves as bedding for farm animals or as a soil treatment. I n Germany such utilization prompted concern over site degradation, and provided a stimulus for Ebermayer’s (1876) classic work on the production and chemical composition of forest litter. This study demonstrated conclusively the importance of litter-fall in the nutrient cycle of the forest, at the same time that its significance in soil development was being shown by Miiller’s (1887) pioneer investigation of the types of forest humus layer. More recent studies of the importance of litter-fall in the forest ecosystem have been reviewed by Lutz and Chandler (1946). I n the future, forest litter may assume additional significance. The current rapid increase in human population, with its consequent pressure on food supplies and accelerated depletion of non-renewable resources such as coal and oil, will eventually necessitate much fuller use of the world’s organic production (cf. Gaffron, 1946). To be thoroughly efficient such utilization must be mainly a t the level of green plants, the primary producers in the food web. It will also depend upon cheaper sources of energy and on great expansion of biochemical engineering, with current plant residues of all kinds serving as raw materials in addition to the present mainstays - agricultural crops, tree boles, and fossil plant deposits of coal and oil. Because much of the world’s land is best suited to the growth of trees, and wood will in any case remain a valuable raw material in its own right, forests will probably be a major source of materials for the new biochemical technology, particularly since mature stands can in certain circumstances be managed economically on a sustaining basis by selective felling. Moreover, forests utilize both light and growing season to a much greater degree than most agricultGa1 crops, especially if the trees arel evergreen. Total yields of forest dry matter compare favorably with those of farm crops, even without the constant cultivation and fertilization the latter receive (Weck, 1955 ;Ovington and Pearsall, 1956; Ovington, 1956). If forest production is to be used with maximum efficiency, the leaves and other debris should be utilized along with boles and slash, since they make up an important part of the total yield (see Table XX, p. 148). One promising use of leaf litter is as a source of protein which could be extracted from the leaves and incorporated into palatable foodstuffs. Such protein is “not as good as milk protein, but is as good as, or even better than, fish meal” (Pirie, 1962). Pirie (1953, 1958, 1961) has provided cogent arguments for attempting the extraction of protein from forest and agricultural waste on a commercial scale, and the cultivation of useful micro-organisms on the residue. The cultivation of edible fungi on beds of forest litter or on the forest floor itself (“fungal farming”) is another use of litter which might add to the world food supply.
103 The harvesting of present edible fungal growth is still inefficient and haphazard. Smith (1958) notes that conifer forests and plantations of Michigan, U.S.A., each year “burst with great quantities of relatively few species of Boletus”. He suggests that lumber companies could harvest the fungus crop as a means of paying taxes and other costs while the trees are growing to commercial size. Glesinger (1949), in a popular account entitled “The Coming Age of Wood”, points out that the cellulose in wood wastes is capable of being used not only as natural fibre, but as reconstituted cellulose in rayon and plastics, and as raw material for hydrolysis to sugar. The sugar can then be used to produce alcohol, high-protein yeast fodder, and a variety of other useful products. Presumably the cellulose in litter materials could also be so employed, though not as economically. It seems likely that the lignin in wood waste and litter, like the cellulose, can eventually become the raw material for a wide range of chemical conversions, whose industrial importance will increase greatly as reserves of coal and oil dwindle and demands for industrial raw materials grow. Brauns and Brauns (1960, pp. 742-9), in their book on lignin chemistry, point out that this substance is already used (though not on a large scale, in proportion to its availability) in the production of vanillin, plastics, ion-exchange resins, soil stabilizers, fertilizers, rubber reinforcing agents, tanning agents, stabilizers for asphalt emulsions, dispersants in oil-well drilling and other processes, and in ceramic processing. New and large-scale industrial uses will undoubtedly appear as the chemistry of lignin is further investigated. Other litter components beside cellulose and lignin may have industrial potential, the oils and resins in Gymnosperm litter being perhaps the most probable example. If litter is to be utilized commercially, harvest methods will need to be developed. Mechanized raking might serve in well-spaced plantations with closed canopy and little ground flora. I n other types of forest some form of vacuum collection might be devised, since the litter material is loose and unattached. Should litter utilization become economic, it will inevitably involve replacement of the nutrient elements present in the organic debris harvested. Nitrogen is probably the most important of these, but phosphorus, potassium and calcium will also be significant (Tamm, 1958). I n time, nitrogenous fertilizers may be synthesized from atmospheric nitrogen a t low cost, through the use of small nuclear reactors which could provide local sources of power in forested areas. The increasing use of human excretory wastes as fertilizers through sewage processing may also enable a low cost return of nitrogen, phosphorus, potassium and other nutrients to forested areas, especially since the costly sterilization needed for the agricultural use of LITTER PRODUCTION I N FORESTS O F THE WORLD
104
J . ROGER BRAY A N D EVILLE GORHAM
sewage will not be necessary in forest areas. Aerial application of various fertilizers may become a widespread technique for economically renewing or improving the fertility of forest soils, as the demand for forest products rises. Even if forest litter does not become an economic raw material in the near future, the study of quantitative aspects of litter-fall remains an important part of forest ecology, dealing with a major pathway for both energy and nutrient transfer in this type of ecosystem. And since litter production is easy to measure in comparison with the difficult and expensive techniques for estimating total net production of forest stands, the possibility that litter-fall might serve as a simple and convenient index to net production provided an additional stimulus for this review. The chief aim of the study, however, is to collate available data on the quantity of litter produced by forests in different parts of the world, -and to assess the influence of environment upon litter-fall under different forest communities.
11. SOURCES OF DATA A. UNPUBLISXED STUDY B Y J . R. BRAY Litter production was measured by Bray from 1957 to 1961 in an Angiosperm forest with a slight admixture of Pinus strobus. This forest occurs on the upper slope of the east bank of the Don River valley at Glendon Hall, Toronto, Canada (43" 40' N, 79' 22' W). It is dominated by Acer saccharurn with a density of 247 treestha. The composition is shown in detail in Table I. I n 1957 and 1958, leaves and stem fragments were collected from the forest floor in late autumn at the close of the period of leaf-fall. These collections were made from 1 f t 2 quadrats (30.5x 30-5 cm) placed at equal intervals along a transect. Newly fallen leaves and any stem material included were lifted intact from the decomposed duff layer in each quadrat. Samples were taken to the laboratory, where each leaf was inspected for signs of decay. If a mesic, calcium-rich leaf (e.g. Acer saccharurn, Fraxinus pennsylvanica) showed only slight decay or tiny holes it was retained as representative of the current crop. If a leaf with a tough, leathery surface (e.g. Quercus boreaZiis, Q. alba) was even moderately decayed, it was rejected as belonging to the previous year's crop. On this basis it was possible to separate the leaves of the current season from those of the previous season in all but a few cases. Samples were then oven-dried at 105°C. I n early winter of 1959, Hty galvanized iron litter pails (0.093m2 in area) were placed in the forest in a regular block pattern. No pail was located beneath a shrub or low sapling which would intercept litter
TABLEI Forest Composition, Glendon Hall, Toronto, Canada Basal area Frequency Density Basal area Importance at breast height index* (treeslha) (m2/tree) (m2/ha) (percentage of total) Density
Acer saccharurn Fraxinus pennsylvanica Pinus strobus Prunus serotina Quercus alba Quercus borealis
247 29 15 44 87 160
-
0.044 0.017 0.128 0.115 0.181 0.116
11.0 0.5 1.9 5.1 15.7 18.6
42.4 6.1 3.0 6.1 18.2 24.2
42.5 5.0 2-5 7.5 15.0 27.5
* Sum of frequency, density and basal area percentages.
20.8 0.9 3.5 9.5 29.9 35.2
106 12 9 23 63
87
106
J . ROGER BRAY A N D EVILLE G O R H A M
from the canopy. Each pail was wired to two adjacent steel posts t o hold it level. The bottom of the pail was slightly above ground surface, and was perforated to allow for drainage of rain and snow melt. A copper screen was placed on the bottom of each pail to prevent tiny litter particles such as bud scales from washing through the drainage holes. Samples were taken at three or more irregular intervals during the year, the major collection being made at the close of leaf-fall. A few leaves blew into the pails in winter and early spring after the canopy opened and leaf-fall was complete. These leaves were discarded from the sample. All stem material in the pails was collected along with that portion of any fallen stem lying directly above the inside perimeter of a pail. All material of animal origin, including fecal matter, was rejected from the sample. Samples from 1960 and 1961 were oven-dried at 70". I n 1958 and 1961 leaf samples were ashed in a muffle furnace at around 550°C for 24 h, to measure mineral content. Litter-fall and ash content are shown in Table 11. The similarity of leaf litter values indicates a rather uniform yearly production. Stem data are much more variable.
TABLEI1 Litter Production in Glendon Hall Forest, Toronto, Canada Litter fall (metric tons/ha/yr) 1957 1958 1960 1961 Mean Leaf, incl. bud scales, fruit Stem, incl. bark Total Ash content of leaves (% d r y w t )
2.8 0.6 3.4
3.2 3.2 6.3
3.2 0.5 3.7
0.8
3-1 3.9
3-1 1.3 4.3
-
7.9
-
9.0
8.4
B. WORLD REVIEW Literature containing data on litter-fall was reviewed in Biological Abstracts, Forestry Abstracts and miscellaneous journals. Coverage is undoubtedly incomplete owing to the wide range of journals and annual reports in which data of this kind are published. Biologists in areas for which data could not be found were consulted for literature references and for unpublished material. We are most grateful to many biologists throughout the world who answered our letters of inquiry. The following have very kindly supplied unpublished data or additional information about published data: Dr D. H. Ashton, Dr J. Brynaert, Dr H. R. De Selm, Mr A. Deville, Mr E. J. Dimock, Mr G. S. Meagher, Mr B. A. Mitchell, Dr J. S. Olson, Dr A. M. Schultz, Dr L. J. Webb, Drs F. D. Hole and G. A. Nielsen.
LITTER PRODUCTION I N FORESTS O F THE WORLD
107
We are especially indebted to the librarians in the reference room of the University of Toronto Library for their expert and unfailing bibliographic assistance.
111. SELECTION AND PRESENTATION O F DATA
A.
CRITERIA FOR ACCEPTANCE
Despite wide variation in methods of litter collection (e.g., raking of cleared surface, cloth or wire screen at soil surface, box or bucket with screen bottom above soil surface) and adequacy of sampling, most of the data examined have been included in this review, in order to obtain maximum coverage. Owing t o the difficulty of equating number, area and type of litter traps, length of exposure, etc., studies of very unequal value have had to be given equal weight. I n the case of Japanese forests (Ohmasa and Mori, 1937) the few data based on less than five plots were omitted. A study by Tarrant et ul. (1951) has been excluded because the data refer mainly to one year's growth of leaves or needles sampled from the lower portion of the crown (G. S. Meagher, private communication). All values based on complete or representative sampling of forest tree canopy have been segregated for separate examination of the yearly standing crop of tree foliage (see Table XIX). No attempt has been made to convert air-dry to oven-dry weights, partly because it has not always been possible to ascertain the method of drying, but also for other reasons. There appears to be considerable variation in weight loss upon further drying. Table I11 shows between 7 and 18% loss in weight by air-dry litter after drying either at an elevated temperature or in vucuo. Ebermayer (1876) reported losses
TABLEI11 Loss of Weight by Air-dried Litter upon Further Drying Material
% weight loss
Fagus sihatica litter Picea abies litter Pinus silvestris litter Fagus silvatica leaves Picea abies needles Picea abies needles Picea abies needles Picea ubiecr needles Populus leaves Bet& litter
18 15 14 9.4 10.0 8.1 6.8 6.9 7.8 10.5
Betub litter
10.8
Angiosperm tree litter Heath and moss litter
8.7 9.5
Drying method
100"c
Authority
Ebermayer, 1876 Ebermayer, 1876 100" c Ebermayer, 1876 Burger, 1925 Burger, 1925 I n vacuo, P,O, Lindberg and Norming, 1943 I n vacuo, P,O, Lindberg and Norming, 1943 100-105" C, 5 h. Lindberg and Norming, 1943 I n vucuo, P,O, AnderssonandEnander,1948 I n vacuo, 20" C Knudsen and Mauritz-Hansson,1939 10@-103°C, 2.6 h. Knudsen and Mauritz-Hansson, 1939 105' C Bray, unpublished In vacuo, P,O, AndrB, 1947
looo c
108
J . ROQER BRAY A N D EVILLE QORHAM
between 14 and 18%, all other losses ranged between 7 and 11%. The average for all data is lo%, whether or not each author's data are combined before averaging. Although air-dry litter may retain appreciable amounts of water, the air-drying process may also result in considerable loss of organic matter. Tamm (1955) reported dry weight losses of 1 to 10% by living pine and spruce needles stored upon moist filter paper during 48 h at room temperature, only about 2% appeared to be lost by respiration. White (1954) observed that needles of Pinus resinosa air-dried for six weeks, and then oven-dried, yielded 9% less dry weight than needles oven-dried immediately at 7OoC. If the needles were left on whole branches during air-drying, the dry weight decline amounted to 14%. It thus appears that in some cases, oven-drying and air-drying of living leaves should give fairly comparable results, since the excess water content of air-dry needles may be balanced by their dry weight losses. Whether the same is true of litter remains to be ascertained. I n any case, differences owing to drying techniques are small compared with variations in litter weight from other causes, and are unlikely to affect seriously any conclusions drawn from the material.
B. ARRANGEMENT The collected records of litter-fall are presented in Table IV, as metric tons of leaves, other, and total litter per hectare per annum (1 metric ton/ha = 892 lb/acre). Owing to rounding off original figures, total litter does not always exactly equal the sum of leaf and other litter. An initial grouping of data is given under four major headings based on broad climatic zones : Equatorial, Warm Temperate, Cool Temperate and Arctic-Alpine. The Equatorial forests are all within a 10" band north and south of the Equator, in Colombia, the Congo, Ghana and Malaya. The Warm Temperate group ranges between about 30" and 40" both south and north of the Equator, including Australia, New Zealand, and southern parts of the U.S.A. (Florida, the Carolinas, Tennessee and California). The Cool Temperate forests in North America range from Missouri and the mountains of California to Minnesota and Quebec, or about latitude 37-47' N; and in Europe from Hungary to Finland, or about 47" to 62" N. Japanese forests are included in this group, for although the mean annual temperature is not greatly different from that of New Zealand, the climate is more extreme, with distinctly cool winters. The scanty Arctic-Alpine data come from stands at 3 000 m altitude in the Sierra Nevada of California, at 800m in southern Norway, and from the Kola Peninsula in the U.S.S.R., the last region being the most northerly at approximately latitude 67" N. Within the broad climatic zones, data are arranged alphabetically by country. For each country the presentation is alphabetically by
TABLEI V Annual Production of Leaf,Other a.nd Total Litter by the Forests of the World Authority
Date
Location
Lat. Long. (approx.)
Jenny el al. Bartholomew et at. Brynaert
1949 Colombia 1953 Congo (Yangambi) p.c. (Ituri)
4s 1N 2N
74w 24E 27E
Laudelot and Meyer
1954
(Yangambi)
1N
24E
Nye
1961 Ghana (Kade)
6N
1w
Mitchell
p.0.
3N
102E
Malaya
Alt. (m)
1700 1800 1650
150
c 600 c 230 c 300 c 450
Ashton
p.c.
Australia (Victoria)
Hatch
1956
(Dwellingup)
Stoate
1958
(Western)
37s
145E
33s
ll6E
c 33s
c ll6E
270
Plant community EQUATORIAL FORESTS Rain forest Forest Ewalyptus saligna Cupressus lwrilanica Mixed forest Musanga ceeropioides, young secondary forest Mawolobium forest Mixed forest Brachystegia forest Dioapyros spp., mature secondary forest Dipterocarpue forest, lowland Dipteromrpus forest lowland Dipterocarpua forest: upland undisturbed Secondary forest, apparently never cultivated, moderately disturbed Secondary forest apparently never cultivated, moherately disturbed Secondary forest apparently never cultivated, mohefately disturbed Dipterocarpue baud%% plantation Druobahnops armnatica plantation Fagraea fragrane plantation Shoreu lepr08uh plantation (close planting) Shorea Zep7osllla plantation (wide planting) FORESTS WARMTEMPERATE (including subtropical) Eucalyptus regnans, mature forest with undergrowth, 47 trees/ha Eucalyptus regnaw, spar forest, 217 trees/ha Eucalyptus regnaw, pole forest, 1013 trees/ha Eucalyptus marginata virgin forest Eucalyptus marginata: pole forest Eucalyptus mnrginata sapling forest Eucalyptue diversieoldr, virgin forest, 0.65 canopy
I=indigenous, E=exotic.
* O=oven
dry, A=air dry.
Origin1 Age
(yr)
I I
E E I I I I I I
Drying methoda
Litter-fall (metric tons/ba/yr Leaves Other T o L 10.2 123
0 22 25
40
8.3 2.9 85
0
7.0
14.9
3.5
15.3 12.4 12.3 10.5 7.2 5.5 6.3
I I I
0
I
0
8.3
I
0
10.5
0
14.4
0
0
I I I
0
I
I
28 28 25 30
0 0 0
9.3 10.9 7.7 14.8
I
30
0
10.2
I
200
4.2
3.9
8.1
I
55
4.1
3.9
8.1
I
25
I I I I
36 c 25
0 0 0
34
3.3
6.9
1.2 2.0 1.6 2.8
1.1 1.1 1.0 2.9
2.4 3.1 2.6
6.7
TABLEIV - continued Authority
Webb
Claudot Miller and Hurst Will
Date
P.C.
Lat.
Location
(North N.S.W.)
Long. (approx.)
Alt.
Warm Temperate Forests-continued Eucalyptus diversieolw, regrowth, 0.87 canopy. Subtropical rain forest, Brgyrodendron Fieus Low suhtropkal rain forest emergent Eucalyptus acmenioides e‘tc. Warm temperate rain forest, Ceratopetalum, Schizotperia Warm temperate rain forest, Ceratopetalum, Schizomeriq Tall warm temperate rain forest with l’riatania eonferta Wet sclerophyll forest, Eucalyptus
c 305 c 15OE
1956 Morocco (Rharb) 1957 New Zealand (Wellington) 1959 (Rotorua)
34N 415 385
zrilularis
7W 175W 176W
Biawell and Schults Blow
p.c. U.S.A. (California) 1955 (Tennessee)
39N 36N
123W 84W
915
De Selm et al.
p.c.
(Tennessee)
36N
848
245
Heyward and Barnette
1936
(N.Florida)
30N
83W
Kittredge Mete
1940 1952
(California) (5. Carolina)
38N 35N
122w 82W
Plant community
(4
Eucalyptus camaldulensia Nothofag? twncata Pinus radzata Pinus radiata P i n w nigra Pseudotsuga ~ z i e s i i Pseudotsuga menziesii L a k t decidua Pintu ponderosa, pure stand Mixed Quercue spp cut over a t 62 yr. Larger trees Q .ldccinea and 9.velutina, Panus virgintuna secondary forest Secondary growth Quercue alba, Q . velulina Q . prinus Pinue palustha second growth, 889 trees/ha Pinus palustns second growth, 1161 trees/ha Pinus palustns second growth, 1947 treeslha Pinus palustns second growth, 2 402 treeslha Pinus caribaea second growth, 1277 trees/ha. Pinus cananenas P i n w taeda, P . eehinata Pinue echinata Pinus taeda Pinus eehinata and mixedangiosnerm8 ~~
l
I=indigenous, E =exotic.
a
0 -oven dry, A=air dry.
Origin‘
Age Drying (yr) method*
Litter-fall (metric tons/halyr) Leaves Other Total
2.7
I
0
3.3
I
0
7.3
I
0
4.5
I
0
5.9
I
0
6.8
I
0
6.0
0 A
4.2 3.5 4.2 5.1 1.5 2.2 2.2 2.1
1.5 3.9 2.0 2.8 1.4 0.7 1.5
0 0
3.8 3.5
0.7 1.0
I
0
2.7
I
0
3.4
I
0
2.7
I
0
3.3
I
0
3.9
I I
0 0 0 0 0
5.0 3.3 4.2 3.8
1 I E
E E P E E I I
I I
I
I I
40 28 45
40 33
45
78 15
20-25 30-40 10 1-60
A A
A A A 0 0
6.0
7.2
6.0 5.7
7.4 6.3 7.9 2.9 2.9 3.7 24
1.3 1.3 0.3 1.6
44 4.6
6.7
6.3
46 4.6
64
TABLEIV - continued Authority
Olson
Date
p.c.
Sims
1932
Biihmerle
1906 Austria
Bray Coldwell and De Long
Location
(Tennessee)
(N.Carolina)
Table11 Canada (Toronto) 1950
(Montreal)
Perina and Vintrova 1958 Czechoslovakia Bornehusch 1937 Denmark (Nsdebo)
Lat. Long. (approx.)
36N
Alt. (m)
Warm Temperate Forest-onlinued Mixed angiosperms and Pinue eehinac Mixed angiosperms and Pinusspp. Mixedsnmosoermq Mixed a n ~ o s ~ e - 6 Mixed angiospem Pinus eehinatu north-facing slope Pinu8cehinatu:south-facina slope Pinua eehina&level upland Liriodendrontulipifera Pqpulua, Frminzlsin sinkhold Querctls Carua Liriodendron lulip$era,ndrth-facing slope Q w m s ,Carya, Liriodendron lulipifera,south-f3cin~slope Quercua Carya, Liriaddrmi .!uZip$era, level upland uercu.9,Carya, Liriodendron valley inwr - uercud forest,unburned Pinus - 8uercus forest,burned
84W
36N
83W
48N
16E
44N
80W
47N
74W
B
COOLT E ~ E R A T E FORESTS Pinua niura plantation Pinus nigra plantation 120 Acer saccharurn Quermsboralis alba slight’admixtnre Pi& %obua’ Beer saccharuna
c 49N c l 8 E 56N 12E
Boysen-Jensen
1930
(Sor0)
56N
12E
Moller Aaltonen (data of Svinhnfvud)
1945 1948 Finland (South)
56N c 62N
12E c22E
Plant community
*I=indigenous, E=exotic.
Origin1 Age Drying (yr) method’
Litter-fall Leaves Other Total (metric tons/ha/n)
I
1-60
0
4.3
1.7
6.0
I I I I I I I I
1-40 1-150 1-50 1-45
0
3.6 46 4.1 4.1
1.1 07
4.6 53 4.7 61
0
0 0 0 0 0 0
09
6.6
6.2 3.8 4.7
I
4.0
I
5.0
I
6.4
I
6.3 3.5 2.0
I I
I I I
37 57 60-200
0 0 0
3.1
I
0
3.4
I I I
0
0 0
A
2.2 1.7 1.7 2.2 1.6
Fagus grandifolia Betula populifolia Pwulus arandidenlata. P. trmuloidee Pi+&spl Piceaabie6,stem diam.6 cm., 7 000/ha Picea abies, stem diam. 10 cm., 3 700/ha P i c a abiee, stem diam.21 cm., 1200/ha Fraxanue excelsior.unthinned Fraxinus excelsior,thinned Fagus silvatica PinUS 8dVestl.is
I
A
1.2
I
A
1.6
Picea abiea
I
O=oven dry, A=air dry.
0.6
I
I I I I
94
1.3
3.5 3.8 4.3
1.4
34
12 12 5-200 A
1.0
TABLEI V - continued Authoilty
viro
Danckelmann
Danckelmann
Date
1056
Location
Lat. Long. (approx.)
Alt.
(Eva)
61N
25E
105
(Vilppula) (Eva)
62N 61N
25E 25E
105 105
(Hyytiala) (Vesijako)
62N 61N
24E 25E
150 110
48N
11E
1887a Germany (5.Bavaria)
18871,
(throughout)
c 50N
(m)
c 10E
'I=indigenous, E=exotic.
Plant community Cool Temperate Forests-continued Belula Pinussilvestris Pinuasilve.at+ Pinussilvestrzd Piceaabies Picea abies Pieeaabia Betula Betula Pinus silvestris,plantations on good soils Pinwr silvestri.8, plantations on good soils Pinus silvertris, plantatibns on good soils Pinus silvestris,plantations on good SOilS Pinus silvestri.8, plantations on good soils Pinus silvestris,plantations on moderately good to poor soils Pinus silvestris, plantationson moderately good to poor soils Pinus silvest7i.8,plantationson moderately good to poor SOUS Pinus stluestrzd,plantations on moderately good to poorsoils Pinus siZvestri8,plantations on moderately good to poor solls
Fagus silvatiea, good to moderately good Soil8 Fugwr silvatiea, good to moderately good soils Fagua silvutieu, good to moderately good soils Fagus silvdica, good to moderately good soils Fagus silvdim, good to moderately good soils Fagus silvatica, fair to poor soils Fagwr silvatica fair to poor oils Fugw silvuth: fair to poor soils Picea at+ Pieea a h 8 O=oven dry, A=air dry.
Origin1
I I
I I I I I I
Age Drying (yr) methoda
50 88 58 68
A 0
78
0 0 0 0 0
I I
86 21-40
0 A
91
0
Litter-fall (metric tons/ha/yr) Leaves Other Total
1.7 1.2
0.6 0.6
1.9 1.9 1.7 1.3
1.0 0.5 0.4 0.5
1.9 2.3 1.8 2.7 2.8 2.4 2.2 1.8 1.5 3.3
I
4140
A
3.2
I
61-80
A
3.2
I
81-100
A
3.1
I
100
A
3.0
I
21-40
A
2.4
I
41-60
A
2.3
I
61-80
A
2.2
I
81-100
A
2.0
I
100
A
1.9
I
21-40
A
3.6
I
41-60
A
4.2
I
61-80
A
4.6
I
81-100
A
5.0
I
100
A
4.6
I
4140 61-80 81-100 21-40 41-60
A A A A A
3.9 4.2 3.1 3.7
I I
I I
3.6
TABLEI V - continued Authority
Ebermayer
Ebermayer (data of Hartin)
Date
1876
1876
Location
(Bavaria)
Lat. Long. (approx.)
c 49N
c 12E
Alt. (m)
Plant community
Cool Temperate Forest&-continued Picea abies Pieea dies Picea abies Fagus silvatica Fagua &vat+ Fagus silvatwa P i c a abies P i c a abiea Picea abies Picea abies Pinus si1veatri.a Pinus 6ilvestri.a Pinua eilvestris Faqua silvatica
Origin'
Age Drying (yr) methoda 61-80 81-100 100 30-60 60-90 90 30 30-60 60-90 90 25-50 50-75 75-100 80 100
A A A 0 0 0 0 0
0
0 0
0 0
A A
Litter-fall (metric tons/hs/gr) Leaves Other Total 3.8 3.6 3.4 3.4 3.4 3.3
4.5
3.4 2.9 2.8 2.9 3.0 3.6 4.0 3.8
TABLEIV - continued Authority
Ohmasa and Kori
Date
1937 Japan
Location
(Kunadacs) (Godollo) . (Era) (Kunadacs) (Retsag) (Godollo) (Ugod) (Rallol (Kunadacs) (Kallo) (Matra) (Kallo) (Kallo) (Godollo) (Retsag)' (Godollo)
Witkamp and van der Drift
1961 Netherlands (Amhem)
Bonnevie-Svendsen and Qjem
1967 Norway (Eidsberg)
Lat. Long. (wwox.)
Ale. (m)
Plant community Cool Temperate Forests-continued Populus (Hungarian szurke) Populue nigra hybrid UZmw (Hungarian venic) Betula
48N
48N
22E 201
c 36N c 136W
62N
I
W W U 8 8Ee8aflo7U
I I
uercue robur
Chanzaecyparisobtuea Pinue denaiflora Pinus thunbergii Thujopsid dolabrata Lark kampferc (leptolepia) Abies eaclutlinensur PieeajEZO6nSd Pieea glehnii Caetanea crenata Betula latifolia Quercuarobur, Betula vem(coda, mor
6E
.nil
60N
11E
160
61N 62N 6ON 6ON
11E 11E 12E 11E
69N
10E
170 330 250 80 250 150 170 50
I =indigenous, E =exotic.
mull Boil b r k Sibirieo on brown earth
Lark silririca on brown earth La& sibirica on iron podzol Lark decidua on iron podzol La& l@ptol,e& on brown earth
Pieea abies on iron podzol Pieea a h 8 on brown earth Picea abies on brown earth Pice0 abkd on brown earth (tram. to nnaroii r"-"".,
0 =oven dry, A =air dry.
Age Drying (yr) method' 24 35 40 30 35 45 70
w c u e robur
~ e i & cerruco~)a,&tletnur rob~r,etc., (Ringsaker) (Storelvdal) (Qrue)
Origin'
I E E E I
83
51
60
70 75 76 12-16 28 45
A A A A A A A A A A A A A A A
A
3.8 1.8 2.5 3.6 3.9 2.0 1.1 1.6 1.6 1.9 1.4 2.3 2.8 1.6 2.7
1.0
3.7
A
2.6
1.6
41
I I I
I I
I E E E I E I I I I
4.4 4.0 4.9 3.6 3.3 3.8 2.7 3.4 4.0 44 4.7 4.6 38 41 4.5 6.0
A
I I
I I I I I I .I
Litter-fall (metric tons/ha/yr) Leaves Other Tow
45
0
2.8
36 60 90 30 80 60 30-40 45-66
0 0 0 0 0 0 0 0
2.8 1.2 2.1 3.4 2.0 3.z 2.0 46
TABLEI V - continued Authority
Date
Location
Lat. Long. (approx.)
Origin'
Age
Drying
I I
90-130 80
0 0
I I I I I
26 39 63 62
0 0 0 0 0
2.5 1.6 1.3
0.6
0.3 0.0
3.1 3.1 1.0 1.0
0.1
1.7
(yr) method'
Litter-fall (metric tOns/ha/yr Leaves Other T o L
1939
(Stockholm)
69N
18E
I
0
1.6
1943
(Stockholm)
SON
18E
Pieea abiea
I
0
3.1
1038 1964
(S.W. Dalama)
(Lurid)
66N 60N
13E 16E
I I
A
2.8 1.7
47N
9E
Mixed angiosperms Betula pubeseens, open parkland (46% canopy) Fagus dlvdiea
York
Ehwald (dataof Liebundgut)
1967 Switzerland (Zurich)
Kendrlck Owen Wright
1069 U.K.(Cheshire) 1964 (N. Wales) 1967 (Roxburghahire)
330 60
61N
11E
69N
18E
63N 63N 66N
1033 U.S.A.(Minnesota) 1030 (hfinnesota)
47N 47N
96W 92W
Anonymous Chandler
1960 1941
(Missouri) (New York)
c 39N
c 92W
1944
(NewYork)
43N
42N
80 80 180 180
3w 4w 3w
Alway et al. Alway and Zon
Chandler
Plant community Cool Temperate Forests-continued Pinus silvestrb on iron podzol Fagus silvatiea on brown earth (trans. to podzol) F a g w siludiea on brown earth Pieea abiee Pieea ab-ia Bet& Populust remula, herb-rich, some Betula and Cmylus Betula pubeacend and hybrids
(Storelvdal) (Brunlanes)
Anderason and Enauder b u d s e n and Yauritz-Hanaaon Lindberg and Norming .Lindquist Sjors
Alt. (m)
77w
._..
7RW
I -indigenous, E =exotic.
Fagus eilvdica Pinus silvegtris Picea suchensis Picea abiet?, light low thinning, 460 trees/ha Pieea abies, medium thinning, 237 treestha Picea abies, heavy thinning, 67 trees/ha Pieea abiea, light crown thinning, 152 trees/ha deer saecharum and Tilia ame&ann Pinus banksiana and P . resinosa Pinus resmnosa Pinus bankaiana Pinus resinosa and P. 8trobun Pinus banksiana Pinus echinata Acer saccharurn and some mixed angiosperms Tilia americana and some mixed angiosperms aneiosDerms Tilia-americana, Tilia americana, Q y e w rubra, Carya cordifomzts Acer saccharurn, QUErcuS rubra, R little Fagus grandifolio Pinus strobus
* 0 =oven
dry, A =air dry.
I
P
A
60
2.0 2.6
19
2.8
0 0 0
4.1 2.1
0.7
1-7 48
E E
30 ,46
0 0
E
46
0
4.3
E
46
0
3.7
E
46
0
I I I I I I I I
60
0 0 0 0 0 0
2.2 2.0 2.2 2.1 2.0 2.0
30-70
0
3.3
I
30-70
0
3.1
I
30-70
0
2.9
I
30-70
0
2.9
I
c24
0
3.1
5.7
4.2
38
TABLEI V - continued Authority
Dimock
Hole and Nieleen Jenny el al.
Date
1958
p.c. 1949
Location
(Washington State)
(Wisconsin) (California)
Lat. Long. (approx.) 44N 42N 42N 44N 44N 44N 44N 47N
43N 37N
74w 76W 76W 74w 74w 74w
74w
123W
89W ll9W
Lnnt
1951
(Connecticut)
42N
73w
Scott
1955
(Connecticut)
42N
73w
Ehwald (data of Abramova)
1957 U.S.S.R.(Velikije Luki)
57N
31E
Ehwald (data of Bykova)
1957
62N
391
Ehwald (data of Nesterov)
Ehwald (data of Sacharov)
1967
1957
(Voronezh)
(MOSCOW)
(Brjansk)
66N
63N
Alt. (m)
Plant community
Cool Temperate Forests--eontinued Pinus atrobus Pinua reainosa Picea abies Picea rubens Tauga canadensis Thuja oceidenlalis Abiea balsamea 330 Paeudotauga menziesii unthiuned 300 Paeudotauga menzicsi( light thinning 320 Pseudotsuga menzhii, medium thinning 310 Paeudotsuga menziesii, heavy thinning 290 w c u a alba Q.vdutina, 420 treespa 1200wrcua kedggii 1800 1 200- Pinusponderoaa 2 200 1500 Wxed gymnosperms Pinua resinoaa Pinus strobus Beer aaccharum, Qww rubra and mixed angiosperms Pinus strobua P i c a abiea with Ozalis &a& ground flora PGea abiea with Vmcini:ummurtillw, grouud Eora Pinus advestria
8
Age
Drying method*
I I E I I I I I I I
65 c24 c24 150 150 65 25 45 46 45
0 0 0 0 0 0 0
I
45
0
(yr)
0 0
Litter-fall (metric tonslhaly~) Leaves Other Total 2.9 3.8 3.9
1.9 1.5
0
1.1
I I
100-125 60-100
0
I
is0
o
2.1
0
46
I I I I
50 30-50
I I I I I I I I
0
4.6
1.5
0
4.0 4.0 2.1
0 A
1.7 4.6
A 20
40
60
80
100
6.2 1.3
0 0 0
0 0
37 2.5 2.3 1.9 2.0 1.3
Pinua silvurtria with Qww
I
A
3.0
Pinus silvurtria with Beer Pinus silveatris with mixed spp. Pieeaabies withSambunwr understory Pica a b h Pinua ailveetris with Vaccinium &is-idaea ground flora Pinus ailvurtris with Colylus under-
I I I
A A A
3.6 4.2 8.2
38E
34E
Origin1
at,nro
I=iudigenous, E=exotic.
* 0 =oven
dry, A=air dry.
45-68
I I
A? A
2.7
0.6
6.9 3.2
I
A
4.7
2.2
6.0
TABLEI V - continued Authority
Date
Location
(Velikije Luki)
Lat. Long. (approx.)
I I
Populus tremula, with Cowlus and some ground flora Populus tremula with Cmylu8, Tilia and much modnd flora P o p u l u hemka-w ~ ith TiEia Acer platunoides add much grdund flora Pinus siluestris with Quercwr Pinus siluestris with Acer Pinus siluestris with Vaecinium sitis-idma eronnd . .. . -- -~~flora Quercusplantation Quercus and Frazinus plantation Quercus, Fraxinus and Caragann lnicrophylla Quercusand deer Quercuswith Begopodiumground flora Quernur with Aegopodium and Carex ground flora Qu.ercu.8,solonetz soil Populus, density 0.75,1688trees/ha (thinned) Pomlus densitv 1.0. 2 460 treeslha (thinned) Populus density 0.8, 988 trees/ha (thinnkd) Populus, density 1.1,1464trees/ha
I
10
0
3.9
I
25
0
4.1
I I I I
50
0
4.9
(Kiev)
51N
31E
1953
(Voronezh)
52"
39E
(Derkul steppe)
52N 49N
393
~~
40E
(unspecified) Sviridova
1960
(Voronezh)
52N
39E
"
Mork
Jenny et al. Levina
1942 Norway (Hirkjolen)
1949 U.S.A. (California) 1960 U.S.S.R. (Kola Peninsula)
62N
37N
67N
10E
119w 37E
800
3 000
0 hi
La
Litter-fall (metric tons/ha/yr) Leave8 Other Total
P i c a abks with mixed angiosperms Pinus siluestris
1957
(Voronezh)
Drying methoda
I I
Ehwald (data of Zrazevskij and Krot) Remezov and Bykova
1960
Origin1 Age (yr)
31E
1957
Sonn
Plant community Cool Teniyeralc Forcsls-- continued Picea abies with Vacciniuni mrrtiUu8 and Ozalis aceloselln groiind flora Picea ubies with Relula sp.
Ehwald (data of Smirnova)
57N
Alt. (m)
I =indigenous, E =exotic.
* 0=oven
dry, A =air dry.
A
3.3
1.6
4.9
0
1.5
0.5
2.0
0 10,45,105 0
2.1
0.6
2.7 2.4
1.3 2.0 4.5
30 60
15
3.3 3.1 4.3
50 c 210 130
5.2 4.1 4.1
25
I
ALPINEAND ARCTICFORESTS Picea abies, very slight Betula admixture Pinue siluestri-9,appreciable Belula admixture Betula Pinus conlorta Pinue siluestris with Cladonia ground flora Pinwr silveetri.8 with H~loconzium ground flora
70 38-90
I I I I I I
c 170 30
A
30
A
55
A
5.4
55
A
4.6
1.4 6.0
5.2
el35
0
0.9
0.6
c200
0
0.5
0.3
0.8
c 105 200
0 0
0.6
0.2
0.8
1.5
1.2 0.6 1.0
118
J . ROGER BRAY AND EVILLE GORHAM
author, which involves some separation of data from the same areas within the U.S.A. and the U.S.S.R.
IV. LITTERCOMPONENTS A. DETAILED LITTER SEPARATION Table V shows that leaf material contributed 60-76y0 of litter for the species listed, branches 12-15%, bark <1-14y0 and fruit <1-17%. Trees with loose dehiscent bark produced considerably more bark litter TABLEV Detailed separation of Litter Cmponents Percentage of total litter Leaf Fruit Branch Bark Other*
Pinua Pinua Pinua Picea Picea-Betulu Betula Quercua Eucalyptua
60 62 69 73 76 71 75 60
11 17 2 5 6
-
t l 15t
12 1-21-+] 12 13
14 11
-
k-,l8-----+I
12 <1 15 9 )-2b+]
<1 6 10 16 -
Authority Perina and Vintrova, 1958
Mork, 1942
Viro, 1955 Viro, 1955 Mork, 1942 Viro, 1955 Nieleen and Hole, p.c. Hatch. 1955
* Flowers, bud scales, fragments, epiphytes, insects.
t Including buds.
than did tight-barked trees. For example, the floor of a Eucalyptus forest was often covered with fallen bark; and Pinw forests, particularly of P. resinosa, also showed a high bark-fall. Bark litter from Pagw, Carpinw and other tight-barked trees was negligible. The variation of fruit litter reflects the widely varying fruit size and production of tree species and the usually short period over which litter is sampled. Curtis (1959) found that an Acer saccharurn forest produced from 99 000 seeds/ha/yr to 13 million seeds/ha/yr. Miller and Hurst (1957) noted great annual variation in seed production by a pure Nothofagus truncata forest, and observed that hot dry summers favored flowering. The occurrence of “mast years” in true beech (B’agw)forests is well known. B. PERCENTAGE O F NON-LEAF LITTER The difficulties of sampling tree stem litter have been noted frequently. Nye (1961) observed that timber-fall over a small area was very erratic and difficult to measure, since it was influenced greatly by the fall of even a single large tree. Data from Toronto (Table 11)
LITTER PRODUCTION IN FORESTS OF THE WORLD
119
showed stem litter ranging from 14 to 50% of total yearly litter over four years. Non-leaf litter data in Table IV range from 2.8% in an angiosperm stand of Bonnevie and Gjems (1957) to 55% in an Angiosperm forest of Stoate (1958). These variations emphasize that stem litter sampling requires larger areas and longer time spans than leaf litter sampling if accurate comparisons of the two are to be made. * On average, non-leaf litter makes up about 27 to 31% of the total, as shown by Table VI. The mean of all values is 30%. Values for AngioTABLEVI Percentage of Non-leaf Material in Forest Litter
All species
Angiosperms Gymnosperms
BY
Individual values
author
30 30 29
30 31 27
sperms are slightly higher than those for Gymnosperms, owing mainly to high values for several Australian Warm Temperate species. If the data are divided into latitudinal zones (Table VII), Warm Temperate TABLEVII Percentage of Non-leaf Litter in Different Climates* Climate Gymnosperms Tropical Warm Temperate, Australia and New Zealand (39) Warm Temperate. North America 37 Cool Temperate 23 Arctic-Alpine (39)
Angiosperms (33) 42 23 21 21
~~
*Figures in brackets represent a single author’s data.
areas tend to have a higher non-leaf litter percentage than Cool Temperate areas. This relationship is especially evident in the Gymnosperm species. Among Angiosperms this tendency is less clear, for while the Warm Temperate forests of Australia include many loose-barked trees (e.g. Eucalyptus), the forests of the southern U.S.A. show lower nonleaf litter percentages similar to those of their Cool Temperate counterparts farther north.
c.
UNDERSTORY LITTER
The contribution of understory plants to forest litter is closely related to the density of the forest canopy and light penetration to the under-
TABLEV I I I Understory Litter Species
Understory litter (metric (yoof total tonslhalyr) litter)
Eucalyptus regnans mature forest, 47 treeslha Eucalyptus regnans spar forest, 217 treeslha Eucalyptus regnans pole forest, 1013 trees/ha Robinia pseudacacia, 9 yr Sassafras albidum, 12 yr Larix leptolepis Larix sibirica Picea abies Pinus silvestris Ulmus glabra and mixed Angiosperms Pinus strobus Acer sacchrum Populus tremula, 30 yr, 2 460 treeslha Populus tremula, 30 yr, 1688 treeslha Populus tremula, 55 yr, 1464 treeslha Populus trernula, 55 yr. 988 trees/ha Quercus robur Mixed Angiosperms, cut in 1940
* Probably includea lower story trees. t Living material harvested in mid-summer.
2*0* 0.9*
0.8*
1.1.t 0.210.3 0.2 0.1
0.2
0.3 0.3 0.3 0.4 0.5f 0.3
0.35 0-1 0.8
25 11 11 28 7 10 7
3 7 10 16 15 8 10 8 6 4 20
Authority
Ashton (P.c.) Ashton (P.c.) Ashton (P.c.) Auten, 1941 Auten, 1941 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Lindquist, 1938 Scott, 1955 Scott, 1955 Sviridova, 1960 Sviridova, 1960 Sviridova, 1960 Sviridova, 1960 Witkamp and van der Drift, 1961 Witkamp and van der Drift, 1961
f Improvement cut 1952, sampled 195S58. 8 Improvement cut 1940-42, sampled 1955-58.
LITTER PRODUCTION I N FORESTS OF THE WORLD
121
story. Data in Table VIII reveal that the maximum contribution of understory plants to total litter is 28% in a very young stand of Robinia, while an old open stand of Eucalyptus reaches 25%. Another high value of 20% is exhibited by a mixed Angiosperm stand (height 6.5-10.5 m) opened by cutting. Other values range from 3 to IS%, and average 9%.
D.
MINERAL MATERIAL
Forest litter is not wholly organic, but always contains some mineral matter. Table I X provides average values for the ash content of litter from Angiosperm and Gymnosperm species in North America and Fennoscandia. I n both regions, the Angiosperm group, and especially the non-fagaceous Angiosperms, contained more mineral material than the Gymnosperm group ; with the majority of Gymnosperms having from 2 to 6% ash, the majority of Fagaceae from 4 to 8% ash and the majority of non-fagaceous Angiosperms from 8 to 14% ash content. Mean ash content as a percentage of dry matter of the nineteen Gymnosperm species was 3-7%, of the thirteen species of Fagaceae 6.3%, and of the forty-three non-fagaceous Angiosperms 10.4%. Among genera summarized in Table I X with two or more species, mean per cent ash contents are as follows : Gymnosperms, Pinus, 3.0; Picea, 4.5 ; Juniperus, 4.6 ;Larix, 5.2 ;Fagaceae, Castanea, 4.4; Quercus, 6.6; F q u s , 6-9; non-fagaceous Angiosperms, Acacia, 4.8 ; Populus, 5.5 ; Betula, 5.8; Prunus, 7-7; Acer, 8.4; Diospyros, 9.0; Fraxinus, 10.7; Aesculus, 14.7; Ulmus, 16.1; Morus, 16.3; Celtis, 21-4. Broadfoot and Pierre (1939) present ash contents of leaf litter from trees in West Virginia, U.S.A., indicating a range of from 2 to 3% dry weight for three Pinus species (P. strobus, P . rigida, and P. virginiana). Juniperus virginiana had 5% ash. Leaf litter from fifteen Angiosperm tree species ranged from 3 to 12% ash. It is noteworthy that ash content is usually low for taxa in Table IX such as Acacia, Betulu, Castanea, Juniperus, Pinus, Populw, and Quercus, which are usually pioneer in forest development and which often occur on the more infertile sites. There is a higher ash content in taxa such as Acer saccharurn, Aesculus, .Celtis, Cladrastis lutea, Diospyros,
Praxinus, Juglans nigra, Liriodendron tulipifera, Magnolia macrophytla, Morus, Tilia americana and Ulmus, which usually occur in the more developed (or “climax”) forest communities and on the more mesic and fertile soils. Ash content of litter may vary with region, owing mainly to soil differences. For example, among the Fennoscandian data, those from Finland tend to be rather low. Detailed analyses of the major elements comprising the mineral material in litter are numerous, and have been reviewed extensively
TABLEI X Ash. Content of Litter from Various Trees ~
~
~~~~~~~~
North America
Ash yo of dry weight
1
Scott, 1955 (freshly fallen leaves or foliage)
"
Joffe, 1949 (old leaves)
*Various authors
Frequency
Gymnosperms
Fagaceae Non-fagaceous Angiosperms
Pinus rigida Pinus silvestris
2
4
Fennoscandia*
2
0
0
Pinus rigida
Pinus reainosa Pinus strobus
Pinus silveatris
4
0
0
Pinus banksiana Pinus cari baea Pinw, palustris Quercus borealis
Abies balsamea Picea rubens Populus grandidentata
Larix leptolepia
6
1
1
Acacia angustissima Caatanea sativa Juniperus pinchotii Juniperus utahensia Pinus resinosa
Betula popal~olia Acer rubrum Castanea vulgaris
3
2
3
3
3
4
Acacia roemeriana Acer rubrum Pinus strobus Quercus alba Quercus breviloba Quercus palustris
Betula pabeacens and vermosa Sorbua aucuparia Larix sibirica P i c a abies
* Anderssonand Enander, 1948. Bonnevie-Svendsenand Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson,1939. Mork, 1942. Viro, 1955.
TABLEIX - continued North America Ash yo of dry weight 6-
Scott, 1955 (freshly fallen leaves or foliage)
Fennoscandia*
Joffe, 1949 (old leaves)
Fagua grandqolia Quercus virginiana sndifolia mnsylvanica 8
9
10
11
Diospyros virginiana Fraxinus excelsior Fraxinus quadrangulata Liquidambar styraci$ua Prunus serotim
*Various authors
1
3
0
Populus tremzclcl Quercus robur
0
3
4
0
0
6
0
0
6
0
1
3
0
0
3
Carya ovata Catalpa speciosa CornusJorida Diospyros texana Magnolia macrophylla Platanus occidentalis Fraxinua americana
Ulmus americana
Robinia pseudmacia
Fagaceae Non-fagaceom Angiosperms
L a r k decidwz Fagua silvatica
Acer smcharum
Liriodendron tulipij'era Quercus douglaaii Tilia americam
Frequency
Gymnosperms
Acer platanoides
* Andersson and Enander, 1948. Bonnevie-Svendsen and Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson,1939. Mork, 1942. Viro, 1955.
TABLEIX - continued North America Ash % of dry weight
-13
Scott, 1955 (freshly fallen leaves or foliage)
-.
Joffe, 1949 (old leaves)
*Various authors
Freauencv
Gymnosperms
Fagaceae Non-fagacsoua Angiosperms
Acer saccharurn
0
0
1
Cladrastis lutea Juglans nigra
0
0
2
Aesculus glabra Robinia pseudacack
0
0
2
0
0
3
0
0
2
0
0
2
Aesculus calijornica Celtis reticulata 16
Fennoscandia*
Fraxinus excelsior
Morus microphylla Morus rubra Celtis occidentalis 26.0
Ulmus scabra 21.3
* AnderssonandEnander, 1948.Bonnevie-SvendsenctndGjems, 1957.Hewelman, 1925.KnudeenandMaurita-Hamson,1939.
Mork, 1942. Viro, 1955.
LITTER PRODUCTION I N FORESTS O F THE WORLD
125
by Lutz and Chandler (1946). Many more recent references may be found in the bibliography at the end of this review. Analyses for several of the minor elements have been made by Scott (1955).
E.
ORGANIC MATERIAL
The organic fractions of forest litter are not a t all well known. Crude proximate analyses of fresh leaf litter from four Gymnosperm and four Angiosperm tree species in eastern North America were carried out according to the methods of Waksman (see Handley, 1954) by Melin (1930), and a similar series of analyses is available for four Angiosperm and four Gymnosperm species in Finland (Mikola, 1954). These may be of interest to persons concerned with the possible utilization of leaf litter. Ether soluble components ranged from 4 to 12% dry weight, coldwater soluble organic matter from 3 to 14%, hot-water soluble organic matter from 3 to 9yo,and alcohol soluble organic material from 3 to 13%. “Hemicelluloses”, estimated crudely from sugars produced by dilute acid hydrolysis of alkali extracts, ranged from 10 to 19% dry weight. “Celluloses”, also crudely estimated by treatment of hemicellulose residues with Schweitzer’s reagent, ranged from 10 to 22%. “Ligninhumus”, the residue remaining after extraction of litter with a mixture containing 10 ml of 18% HC1 and 50 ml of 72% H,SO,, ranged from 5 to 33%. “Crude protein”, estimated by subtracting water-soluble from total nitrogen and multiplying the result by 6.25, ranged from 2 to 15% dry weight. Differences between Gymnosperms and Angiosperms were not consistent. Handley (1954), in discussing such analyses, cites some by Wittich (using methods somewhat different from those above) of German Angiosperm tree litter. These give the following ranges, as percentage of ash-free d q matter: ether soluble 6-14, coldwater soluble 6-25, hot-water soluble P 1 0 , alcohol soluble 2-5, hemicelluloses 25-36, celluloses 7-25, lignin-humus 11-30 and lignin (by acetyl bromide separation) <1-8. Nykvist (1963) has recently investigated the water-soluble aminoacids, sugars and aliphatic acids in Angiosperm and Gymnosperm litter from Swedish forest tree species.
V. FACTORS AFFECTINGLITTER-FALL A.
EVERGREEN GYMNOSPERMS AND DECIDUOUS ANGIOSPERMS
Because of their evergreen nature, Gymnosperms might be expected to be more productive than deciduous Angiosperm trees, although this factor may be countered to some extent by the tendency for Angiosperm forests to occupy more fertile sites. As far as litter-fall is concerned, Table X indicates that when a wide range of sites is considered I2
C.E.R.
126
J . ROGER BRAY A N D EVILLE QORHAM
TABLEX A Comparison of Litter Production by Evergreen and Deciduous Trees in the Northern Hemisphere
Evergreen Deciduous Gymnosperms Angiosperms (metrictons/he/yr) 3.7 3.2 2.6 2.4
No. regions averaged
Total litter Leaf litter
by difference
Other litter observed
8 9
4
1.1 0.7
0.8
0.7
Gymnosperms yield about one-sixth more total litter annually than Angiosperms, the difference amounting to 0-5 t/ha. The difference for leaf litter alone is 8% (0.2 t/ha), and for those stands where other litter was actually collected the Gymnosperm yield was about the same as that of Angiosperm trees, 0.7 t/ha. (In computing averages from combined data, only those countries or states were considered for which both evergreen Gymnosperm and deciduous Angiosperm stand data were available. The averages in Table X, and in Table XI, are based on combined data for each country, with each American or Australian state, TABLEX I Annual Litter Production in Four Major Climatic Zones Leaves Other Total no. regions metric no. regions metric no. regions metric averaged tons/ha averaged tons/ha averaged tons/ha Arctic-Alpine
1
0.7
1
0.4
3
1.0
15
2.5
10
0.9
22
3.5
Warm Temperate
8
3.6
5
1.9
7
5.5
Equatorial
2
6.8
1
3.5
4
10.9
Cool Temperate
and the Werent major areas of the U.S.S.R., treated as countries, except for the following which are grouped - the New England states, the Carolinas.) Data on net production (Table XX) support the generalization that Gymnosperm trees are somewhat more productive than Angiosperm trees, the difference amounting to about one-quarter (2.6 t/ha) for total above- and below-ground production. For leaves the difference is slight (see also data on standing crops of leaves in Table XIX). Specific areas do not always follow the above tendency. For example, within Germany the averages of data in Table I V show somewhat
L I T T E R PRODUCTION I N F O R E S T S OF T H E W O R L D
127
greater total litter production by the deciduous F q u s silvatica, 3.8 t/ha, than by the evergreens Picea abies, 3.5 t/ha, and Pinus silvestris, 3.0 t/ha. If only Ebermayer’s individual data are examined a somewhat different situation is evident, with Fagus averaging 3.3, Pinus 3.2 and Picea 3.0 t/ha (Lutz and Chandler, 1946). B.
ENVIRONMENT
7. Climate and Latitude The predominant influence of climate upon litter production is shown in a general way by Table XI, which summarizes the data for major climatic zones. I n Arctic-Alpine forests total litter production averages 1 t/ha annually, while in Equatorial forests the mean is almost 11 t/ha.i Cool and Warm Temperate forests average 3.5 and 5-5 t/ha respectively. I n round figures the ratios are about 1: 3 : 5 : 10 for the major climatic zones. The range of mean annual temperature spanned by these climatic zones is from below freezing for the most northerly Arctic forests to about 25°C for those of the hottest Equatorial regions. From a biological standpoint the length of the period when temperatures are above freezing is also important. It is of course year-long in the Equatorial forests, and almost so in the Warm Temperate stands; but in Arctic-Alpineregions the mean daily temperature may be above freezing for 6 months or less. The growing season may be considerabIy shorter, for example Paterson (1961) indicates that in parts of northern Fennoscandia the growing season for Gymnosperm forests may be as short as 3 months per annum, while in .Cool Temperate forests it is often about 6 to 7 months in duration. Associated with the higher temperature and longer growing season of the Equatorial zone is the greater amount of insolation during the period of photosynthesis. This must be of considerable importance for primary productivity. Some preliminary calculations based on maps of Black (1956) suggest that the total amount of solar radiation received during the growing season is roughly in the proportion of 1: 3 : 5 for extreme Arctic-Alpine, Cool Temperate and Equatorial sites. I n the Arctic-Alpine sites it is probably less effectively utilized owing to the more open nature of the forest and to the relative coldness of the soil. Data for both leaf and other litter, while less extensive than those for total litter, bear out the general climatic relationship. (In this con-
t I n view of the scarcity of tropical data it may be of interest to note a total annual litter-fall of 14 t/ha by Eucalyptus in Brazil, measured over 8 years (Navarro de Andrade, 1941).This value has not been included in the tables because no further information ia available, particularly as to whether this is dry weight (though it seems unlikely to be otherwise).
128
J . ROGER BRAY AND EVILLE QORHAM
nection it should be borne in mind that the three categories of litter summarized in Table XI do not represent matched sets of data, for some authors collected only leaf litter, and some of those collecting total litter did not separate leaf and other litter.) Leaf litter ranges from 0.7 tjha in Alpine Norwegian forest to nearly 7 t/ha in Equatorial Africa, with the Cool and Warm Temperate zones intermediate a t 2.5 and 3.6 tjha respectively. Data for non-leaf litter are least satisfactory, with less coverage and also less reliability because of the irregular and '4t
NORTH
O R SOUTH LATITUDE ( d e g r e e s 1
FIG.1. Annual production of total litter in relation to latitude. Open triangles equatorial, solid triangles -warm temperate, circles - cool temperate North American (open)and European (closed),squares -Arctic-Alpine. Line fitted visually to means for climatic zones, shown by large crosses. One alpine Californian stand is excluded.
occasional deposition of large branches upon collecting sites. However, even in this instance the annual production in the Norwegian mountains is about one-ninth that in Ghana, 0.4 as against 3.5 tjha. Again the Cool and Warm Temperate forests are intermediate, with 0.9 and 1.9 t/ha. The major role of temperature in controlling litter production is well illustrated in Fig. 1, where total annual litter-fall is plotted versus latitude. The relationship is inverse and linear, with a maximum level of over 11 t/ha at the Equator declining steadily to a little less than 1 t/ha a t latitude 65" N in Europe, where forest grades into tundra. Fig. 1 reveals that litter production in central and north European forests is about the same as that of similar Cool Temperate forests in
129 the northern U.S.A. and Canada, although the European sites are on average about 10 degrees farther north. The warming effect of the Gulf Stream upon European climate is probably the major factor involved, but it is also possible that the intensive management of European as compared with North American forests is important in this connection. LITTER PRODUCTION I N FORESTS OF THE WORLD
2. Altitude and Exposure Ebermayer’s (1876) data for Fagus silvatica, Picea abies snd Pinus silvestris have been summarized by 200 m altitude classes from 250 to 1 250 m. This analysis, in Table XII, indicates a peak litter production at the intermediate elevations from 450 to 850 m, although no species covers the entire altitudinal gradient. The data for Picea are most complete, and show peak litter-fall between 650 and 850 m. There is a tendency in mountainous areas for rainfall and temperature conditions to be optimum for forest growth at intermediate elevations. At higher elevations, temperatures are too low and winds too severe for luxuriant tree growth, and at low elevations, there is often a decreased rainfall. Whether these conditions apply to the data in Table XI1 is not known. TABLEXI1 Litter Production and Elevation in German Porests Elevation
(4 250
650
1050
Fagua ailvatica Picea abies Pinw, silvestris (total litter, metric tons/ha/yr) 3.8
-
3.3
4.1
3.4
6.0t
5.9*
3.9
-
3.6
-
3.1t
1250
* One value.
t Two values.
Ebermayer’s material was also divided into four exposure quadrants, NE, SE, SW and NW. Values from cardinal points (N, E, S, W) were divided in half and assigned to each of the adjacent quadrants. The results of this analysis are given in Table XIII, and indicate a lower litter production in westerly than in easterly quadrants. The highest average litter production was on the NE slope, generally considered to be least exposed to the heating and drying effects of insolation ; while
130
J. ROGER BRAY AND EVILLE GOREAM
TABLEXI11 Litter Production and Exposure in German Forests* Total litter production, metric tonslhalyr
Exposure
Total no.
Fagus silvatica
Picea abies
Pinus silvestris
Mean
Mean weighted by no. of stands
4.1 4.4 3.9 4.1
4.7 3.7 2.5 3.6
4.0 3.7 3.8 3.6
4.3 3.9 3.4 3.8
4.3 3.8 3.2 3.7
NE SE SW
Nw
stands
14.5 10.0 15.0 23.5
* From data in Ebermayer f1876). the lowest average litter production occurred on the most exposed (SW) slope. The greater average exposure effect of SW as compared with SE slopes is presumably owing to maximum reception of insolation on SW slopes in the afternoon, when the air is warmest, driest, and usually clearest. Thus insolation and evaporation maxima tend to be greatest on SW slopes.
3. Soil Fertility The influence of site class on litter production, with special reference to soil fertility, is shown in Table XIV. Site class designations are the European “bonitat” grades of decreasing fertility from I to V. Table XIV generally shows decreasing litter-fall with a decline in site quality,
TABLEXIV Litter Production and Soil Fertility in German Forests Species
Pinus szhestris
Piceu abies Fagus silvatica
Authority
Site class
Total litter (metric tonslhalyr)
I 1-111 I11
3.0 3.2 2.0 2.2 1.0 3-8 3.0 3.5 4.4 2.5 3-9
Zimmerle, 1933* Danckelmann, 1887a Wiedemann, 1948* Danckelmann, 1887a Wiedemann, 1948* Zimmerle, 1949* Wiedemann, 1936* Dietrich, 1925* Danckelmann, 1887b Wiedemann, 1931* Danckelmann, 188713 ~~
m-v
V I I11 I 1-111 I11 111-V ~~
* Cited by EhwaId (1957).
.
LITTER PRODUCTION IN FORESTS OF THE WORLD
131
although for Pagus silvatica the data fiom nineteenth- and twentiethcentury authors require separate consideration. The data for Pinus silvestris provide the clearest indication of a site effect, with litter production on the poorest site (V) one-third that on the best site (I).The intermediate site class (111)produces two-thirds as much littgr as the best class. Data of Bonnevie-Svendsen and Gjems (1957) also indicate higher litter-fall on more fertile soils in Norway. Mean litter production for Larix spp. is 1-6 t/ha on iron-podzol and 2.8 t/ha on transitional and brown-earth soils. For Picea abies the corresponding figures are 2.0 t/ha and 3.2 t/ha respectively. 4. Soil moisture Litter data from Ebermayer (1876) for Pinus silvestris and Picea abies are shown in Table XV from mesic and dry soil moisture sites.
TABLEXV Litter Production and Soil Moisture in German Forests* Species
Pin- silvestris P i n w silvestris Picea abies Picea abies
Soil moisture
No. of sites
Total litter (metric tons/ha/yr)
Mesic
6 11 31 2
4.0
Dry
Mesic
Dry
3.5 3.8 2.3
* From data in Ebermayer (1876). The decrease in litter-fall from mesic to dry conditions is especially marked for Picea, a mesic species, and less noticeable for Pinus, which tends to occur more often on exposed dry sites.
c.
TREATMENT
1. Plantations and Native Forests Only one study (Ohmasa and Mori, 1937) gives sufficient data to allow comparisons of litter-fall in natural forest stands and plantations. I n both Chamaecyparis obtusa and Pinus densijiora there is no significant difference between mean litter-fall in plantaJion and forest. Investigation by Mitchell (private communication) of a variety of indigenous Malayan species yields a mean value of 8-7 t/ha for natural communities and 10.6 tiha for plantations, not necessarily of the same species. 2. Influence of Tree Density and Basal Area Within closed-canopy forests litter production appears to be little affected by differences in tree density, as shown in Table XVI. Com-
132
J . ROGER BRAY AND EVILLE GORRAM
TABLEXVI Litter Production and Tree Density Species
Authority
Fagw silvatica
Moller, 1945
Populus trernula
Sviridova, 1960
Pinus paluatris
Heyward and Barnette, 1936
Pinus ponderosa
Biswell and Schultz (P.c.)
Density (treeslha), 179 233 244 248 281 317 901 908 1173 5 842 6 732 988 1464 1688 2 460 889 1161 1 947 2 402 1196 1495 2 931 3 459
Litter (metric tons/ ham) 2.8 2.3 2.3 2.6 2.7 2.5 2.9 2.8 2.6 2.2 3.0 5.0 4.2 5.4 4.9 2.7 3.4 2.7 3.3 2.6 2.0 1.8 2.1
parison of eleven stands of Fugw silvatica (Moller, 1945) by a rank correlation test showed no significant correlation ( p>0.10) between litterfall and tree density. Similarly, studies by Sviridova (1960), Heyward and Barnette (1936) and Biswell and Schultz (Schultz, private communication) failed to show any consistent relationship between these two variables, although in each of these instances only four stands were compared. I n Norway Bonnevie-Svendsen and Gjems (1957) have shown a distinct correlation between annual fall of leaf litter and stand basal area in a series of Gymnosperm and Angiosperm stands. Litter-fall averaged about 70-75 kg per m2basal area, over a basal area range from 8 to 40 m2/ha. In Missouri (U.S.A.),Crosby (1961) has demonstrated a correlation between total litter-fall of Pinus echinata and stand basal area, but in this case an increase from minimum to maximum basal area coverage of three-fold only doubled the annual litter-fall. The stands of low basal area had been thinned a few years prior to litter collection, and presumably the less productive trees were removed.
LITTER PRODUCTION I N FORESTS O F THE WORLD
133
3. Effect of Thinning If a closed-canopy forest is thinned there is a decrease in litter production which is roughly proportional to the degree of thinning. Data in Table IV demonstrate this relationship for Pseudotszqa menziesii (Dimock, 1958), Picea abies (Wright, 1957) and Fraxinus excelsior (Boysen-Jensen, 1930). I n all cases the control stand has the highest litter-fall and the most heavily thinned stand the lowest. Moller (1945) has shown the effect of thinning upon the standing crop of Fagus silvatica leaves. With no thinning, leaf crop was 2.0 tiha, with Bregentved thinning 1.9 t/ha and with Vemmetofte thinning 1.7 t/ha.
4.'Effect of Litter Removal Rights to utilize forest litter still existed in Germany in 1954, particularly in Bavaria, where it sometimes caused extreme reduction of forest growth (Mayer-Krapoll, 1956). By comparing areas with and without rights to litter utilization, it has been estimated that annual forest output may require forty years to recover from long-continued litter removal. The loss of nitrogen in the litter is believed to be of especial significance in lessening forest productivity. Wiedemann ( 1951) presented data from study plots (Hermeskeil143,146, Table 363, p. 260) indicating that twenty-five years of litter utilization reduced basal area increase by about two-thirds. Thirty years were then required for recovery.
D.
THE TIME FACTOR
1. Seasonal Variation If forest litter is ever to be utilized economically, it will be of importance to know the pattern of litter-fall, whether distinctly seasonal, or more or less continuous. Such knowledge is also of the utmost importance to students of population dynamics in organisms responsible for litter breakdown, and may be of interest to persons concerned with the role of organic matter in soil development. The pattern of litter-fall varies greatly, as demonstrated by Figs. 2-5. I n the Equatorial forests of Ghana, Colombia and Malaya litter-fall is continuous throughout the year, but with a tendency for slightly greater deposition during the first half of the year. I n Ghana a, short dry season in January and February was noted as leading to increased leaffall (Nye, 1961). Laudelot and Meyer (1954) state that at Yangambi in the Congo there are two minima in the wet seasons and two maxima at the ends of the dry seasons. According to Deville (private communication) seven-year plantation of Acacia decurrens showed highs in
134
J. ROGER B R A Y AND EVILLE G O R H A M RAIN FOREST, COLOMBIA,
40
REP.
TOTAL
40
20
20 -I -I
2 !x
0
20
k J
O
2
40
.
0
.
RAIN FOREST, GHANA, TOTAL
40
w I-
.
40 20
.
(I)
.
( 2.)
0
UNDISTURBED DIPTEROCARP FOREST,
MALAYA,
TOTAL
40
20
20
(3)
0
n
w n.
3 I
40
5
20
=
o
0
.
o
40
.
.
.
.
.
SECONDARY FOREST, MALAYA,
.
.
.
.
.
TOTAL
40
20
.
.
.
.
.
.
.
.
.
.
.
SHOREA LEPROSULA [INDIGENOUS 1 PLANTATION, MALAYA
1 JAN.
(3)
0 40
20
20 0
0
(31
/
FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT.' NOV. OEC
0
FIG.2. Seasonal litter-fall in equatorial forests. (1) Jenny et al., 1949;1(2) Nye, 1961; (3) Mitchell (P.c.).
December (18% of total litter-fall) and June (llx), with lows in May (3%) and August to September (5% each). It should be noted that many individual species of indigenous tropical rain forest are distinctly deciduous, though not necessarily tied to any sort of annual cycle. The pattern and timing of leaf replacement is extremely variable, and dependent upon both external and internal factors (see Richards, 1957, pp. 193-8). I n the Warm Temperate forests of eastern Australia, Fig. 3 shows that litter-fall goes on throughout the year, but with a distinct maximum in spring and early summer (October to December). Precipitation generally increases along with temperature during this period in eastern Australia (Walter and Lieth, 1960). I n the Eucalyptus regnans forests of Victoria, Australia, Ashton (private communication) reports about nine times as much leaf-fallin summer as in winter. I n western Australia both young and old forests of Eucalyptus marginata deposit leaf litter mainly from January to March, the warm dry part of the year. Other litter falls irregularly throughout the year, but with slightly greater intensity at about the time of maximum leaf-fall (Hatch, 1955). Eucalyptus diversi-
LITTER PRODUCTION I N FORESTS OF THE WORLD
40
:AST
AUSTRALIAN
FORESTS,
136
LEAVES SCLEROPHYLL
20
2 a
40
w
20
5
0
2 a
40
I-
I-
W
20
0
: o a
3
I I-
z
0
E
0
0
-t
-t
40 20
O 40 20 0
I I R G l N EUCALYPTUS MARGINATA, WEST A U S T R A L I A
-
OTHER
PlNUS NIGRA,
NEW Z E A L A N D
LEAVES
P l N U S RADIATA, LEAVES
-.-,#'
.___-______ --0
NEW Z E A L A N D
40
OTHER
*A,
'---
...
,
A
- 20
(4)
I-
FIG.3. Seasonal Litter-fd in forests of the southern hemkphere. (1) Webb (P.c.); (2) Hatch, 1956; (3)Miller andHurst, 1957; (4) Will, 1959.
color in western Australia shows a similar pattern of litter deposition (Stoate, 1958). I n New Zealand the peak leaf-fall of Nothofagus truncata is connected with the development of new leaves in the spring months of October and November (Miller and Hurst, 1957). The main fall of non-leaf litter takes place 2 months earlier. For the exotic northern Gymnosperms Pinus nigra, P. radiata and Larix decidua in New Zealand, maximum needle-fall occurs in autumn (March to May), according to Will (1959). While precipitation is rather uniform, March is the driest month of the year (9.4 mm) and June the wettest (14.5 mm). Pseudotsuga menziesii shows no definite seasonal trend. I n all species the fall of non-needle litter is more affected by storms than is needle-fall, which does however show some storm influence. The main period of non-needle litter deposition is clearly mid-winter (June to July) for Pinus nigra, the peak coming about 2 months after cessation of needle-fall. The pattern is less regular for Pinus radiata, the average over 4 years showing one peak near the time of maximum needle-fall and another about 5 months later. The Warm Temperate forests of Tennessee in North America also
136
J . ROGER BRAY A N D EVILLE QORRAM
40
20
0 40
rENNESSEE FORESTS, TOTAL UPLAND PINUS
20
0
0 40
i
FINNISH FORESTS,
LEAVES
(
20
3)
LL 4
a
0
-
40
u
-I W
20
13
3 0 z a u Q
40
20
*- I I 0
I
0
40 20
'ICEA
ABlES SCOTLAND, TOTAL
--
DENMARK, LEAVES
------__-h
_ . I -
40
20,
SITCHENSIS,
WALES,
---_--_
LEAVES YEAR OF LOW L E A F F A L L
YEAR ' O F 4IGH L E A F F A L L
20
(6)
~.0
0 'ICEA
.40
'
.40
0 40
20 0
IAPANESE GYMNOSPERM FORESTS, PlNllS IENSIFLORA
LEAVES
CRYPTOMERIA
oOTUSA
.. AN.
FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
0
FIG.4. Seasonal litter-fall in forests of the northern hemisphere. (1) Witkamp and van der Drift, 1961; (2) Olson (P.c.); (3) Viro, 1955; (4) Kendrick, 1959 and Danckelmann, 1887; (5) Mork, 1942; (6) Wright, 1957 and Bornebusch, 1937; (7) Owen, 1954; (8) Ohmasa and Mori, 1937.
show a seasonal pattern, although some leaf-fall is observed throughout the year (Fig. 4). Angiosperms exhibit a distinct autumnal peak as the weather cools, while the seasonal effect is much less for Pinus echinata (Olsen, private communication). For Pinus echinata farther north in
137
LITTER PRODUCTION IN FORESTS O F THE WORLD
Missouri it is reported (Anon., 1960) that 60% of litter-fall occurs in the 3 months from September to November. I n Cool Temperate forests seasonal patterns of litter-fall are often striking (Fig. 4), with autumnal cooling leading to more or less complete leaf-fall in deciduous species, as shown by the graphs for Dutch Quercus and mixed Angiosperms, and for Finnish. Betula. I n New Hampshire (Anon., 1932) it is reported that four-fifths of the mixed Angiosperm litter-fall over the seven months June to December occurs in October. Among Gymnosperms the pattern of deposition ranges from distinctly seasonal, as in the various stands of Pinus silvestris represented in Fig. 4, to irregular throughout the year, as is the case with Picea abies in the stands shown. Chandler (1944) has noted however that Picea abies planted in the north-eastern U.S.A. shows distinctly lower needlefall in spring and summer than at other times of year. In contrast irregular collections by Lindberg and Norming (1943) in Sweden showed high rates of needle-fall during late spring and early summer. Picea sitchensis in Wales showed a rather irregular pattern of needle-fall whether the total for the year was high (1946-47, with a very cold winter) or low (1947-48). There was however a slight tendency for spring and autumn maxima. Such a bimodal spring and autumn pattern of needlefall was more strongly exhibited by Japanese stands of Cryptmeria japonica, Chumaecyparis obtusa and Pinus densijora. TABLEXVII Speci,fic Differences in Leaf Fall within an Upland Oak Porest in Tennessee, U.S.A. Leaf fall as per cent of total for each species Late August Overstory Understory Miscellaneous
Quercw velutina Quercus coccinea Cornus sp. Oxydendrum arboreum Nyssa sylvatica Quercw alba Quercw montana Quercus falcata Quercw stellata Aeer rubrum Carya sp. Pinw echinata
* Balance of 10% overwinters, 5 % ~
~
0 1 3 1 63 0 0 0 0
0 0 0
MidOctober 3 12 72 99 37
16 4
43
71 32 52 20
Early December 97 87 25 0 0 74* 96 57 29
68 48 80
~~~~
falling by February and the remainder by April.
138
J. ROGER BRAY AND EVILLE OORHAM
The difference in leaf-fall periodicity of different species within mixed forest has been shown clearly by Blow (1955), working in upland oak forest of eastern Tennessee in the U.S.A. Table XVII shows the percentage of leaf-fall during the year 1948-49 which was collected by late August, mid-October and early December. From this table it appears that the overstory species lose their leaves later than the understory species, and that even within these groups there are distinct specific differences. The only species in this forest which retains many leaves (10%) through the winter is Quercus alba, although a few remain REF
40
u. LK
W I-
t
40-
MALAYAN FOREST ANISOPTERA
M A L A Y A N FOREST,
SHOREA
SHOREA
LAEVIS
.
I
11)
.20
QUERCUS
N E T H E R L A N D S FOREST
I
.
- 40
20-
-3
40
+ 60 z
*
0
T R EM U L A
40
20
20 0
J A N . FEB. MAR. APR. MAY JUNE JULY
AUG. SEPT OCT. NOV. DEC.
FIG.5. Seasonal litter-fall of individual species in mixed forests. (1) Mitchell (P.c.); (2) Witkamp and van der Drift, 1961.
on Quercus stelbta. Apparently overstory species may lose their leaves earlier than understory species, or even understory individuals of the same species, in other areas, as for example in mixed savannah forest of NW Thailand (Ogawa et al., 1961). Pig. 5 shows the marked variation in litter-fall periodicity among mixed Angiosperms in the Netherlands (Witkamp and van der Drift, 1961). Populus tremula and Quercus robur show distinct peaks of litterfall in October and November respectively. Betula verrucosa also reaches a peak in October, but litter-fall is quite heavy in August and September as well. Alnus glutinosa is unusual in exhibiting a bimodal pattern, with many green leaves being shed in July in addition to the major fall of brown leaves in October. Tadaki and Shidei (1960) found that in a
139
LITTER PRODUCTION IN FORESTS O F THE WORLD
3-year-old Ulmus parvifolia stand, there was a decreasing attached leaf weight of from 438 g/mz on 20 May t o 297 g/m2 on 27 July. This decrease, which equaled 31% of the total leaf canopy by weight and was the result of a loss of all the lower and more shaded leaves, may be more typical of young sapling stands than of forests of adult trees. Individual species in Equatorial forests may also show seasonal variation, t o a lesser degree than in most Temperate forests but t o a, greater degree than the Equatorial mixed forest as a whole. rig. 5 shows a more or less bimodal pattern for three Malayan species, which may be compared with the data for whole Malayan forests in Fig. 2. 2. Annual Variation Total litter-fall may differ greatly in different years, as illustrated by data, in Table XVIII. Owing to variation in sampling procedures these TABLEXVIII Annual Variation of Total* Litter Production in Stands Sampled for Four or More Years (muximumlminimum ratios) Species EQUATORIAL FOREST Mixed secondary forest, Malaya EVERGREEN ANGIOSPERM Nothofqua trunmta, New Zealand DECIDUOUS ANGIOSPERMS Acer sacccharum mixed forest, Canada Popdua plantations. U.S.S.R. Quercua alba, Q. velutina, U.S.A. Betula, Norway Fagua silvatim, 30 to >90 yra, Germany GYMNOSPERMS EVERGREEN PiGea abies, Germany Picea abies, Norway Picea abies. Germany Pinua silvestris, Germany Pin- silvestris, Germany
Authority
No. yeam Max/& sampled litter-fall
Mitchell (P.c.)
4
1.1
Miller and Hurst, 1957
4
2.7
Bray Sviridova, 1960
4 4
1.8 1.1
Hole and Nielsen (P.c.) Mork, 1942
5 6
1.4 1.3
Ebermayer, 1876
7
1-3
Krutzsch, 1869 4 2.4 Mork, 1942 6 I -4 Ebermayer, 1876 7 1*5 Krutzsch, 1869 4 1-3 Krutzsch, 1869; Ebermayer, 1876 7 2.2 Pinua nigra, Austria Bohmerle, 1906 12 5.1 Pinua reainosa, U.S.A. Lunt, 1951 21 3.4 Pseudotsuga menziesii, U.S.A. Dimock, 1958 6 3.2 * In the few caaes where leaf litter was measuredseparatelyresults were similar.
140
J. ROGER BRAY AND EVILLE GIORHAM
values are not always strictly comparable, and it may be observed that for Angiosperms sampled over 4 years the ratio of maximum to minimum annual litter-fall may be as high as 2.7 (in a New Zealand Nothofagus truncata forest). The highest ratio for Northern Hemisphere deciduous Angiosperms is 1.8 for Acer saccharurn mixed forest. Records over 7 years yield no higher ratios. Data for Gymnospermsinclude some much longer periods of comparison, and the greatest annual variation is recorded for a Pinus nigra stand observed over 12 years, the maximum/minimurn ratio being 5-1. I n general the longer periods of observation yield higher ratios, as expected. Over comparable periods in the North Temperate zone, Gymnosperms tend to show high ratios a little more frequently than Angiosperms. It is well known that the longevity of evergreen Gymnosperm leaves depends upon both internal and external conditions, so that fluctuations from year to year in the environment might be expected to affect the leaf-fall of such species more than that of deciduous Angiosperms whose leaves are necessarily shed every year. The single 4-year ratio for Equatorial forest is very low, at 1.1, as might perhaps be expected where climatic fluctuations are not very severe. The fall of non-leaf litter has not often been measured over several years, but annual variation in the four recorded cases is relatively high, maximum/minimum ratios over 4-6 years ranging from 1.9 for Nothofagus truncata (Miller and Hurst, 1957) to 11.9 for Quercus forest (Hole and Nielsen, private communication). Bray recorded a ratio of 5.8 for Acer saccharurn mixed forest and Mork (1942) a ratio of 3.7 for Betub. Such wide variation is to be expected, since the fall of branches is a very local phenomenon of great weight where it occurs. Among environmental factors mentioned as associated with abnormal litter-fall are storms (Picea abies - Bornebusch, 1937; exotic Gymnosperms in New Zealand -Will, 1959; Betula - Knudsen and MauritzHansson, 1939), which may have a very great effect on twig and branch litter-fall. Insect attack may also be important (Picea abies - Mork, 1942). Dryness has been remarked as a factor in high Picea abies needlefall (Bornebusch, 1932), but in contrast Witkamp and van der Drift (1961) observed that in the Netherlands three surface-rooting deciduous species exhibited distinctly low litter-fall during a dry summer, while a fourth deep-rooting species yielded only slightly less litter than usual. I n New Zealand, Miller and Hurst (1957) reported that hot dry summers favor flowering of Nothfagus truncata, and since leaf bud production for the following year’s foliage varies inversely with flowering, a lower subsequent leaf-fall would be expected. Cold temperatures may also increase litter-fall, for Owen’s (1954) data on Picea sitchensis in Wales show nearly twice as much needle deposition in 1946-47, when the
LITTER PRODUCTION I N FORESTS O F THE WORLD
141
winter was extremely cold, as in the following year. Dimock (1958) also reported for Pseudotsuga menziesii in Washington state, U.S.A., that in the 10 months following a severe cold spell litter-fall amounted to nearly three times that of previous years. Viro (1955) in Finland found that the cold September of 1949 led to early leaf-fall in Betula, while the warm September of 1947 led to late leaf-fall. Mork (1942) has suggested that cool temperatures during leaf development may lead to a light litter-fall later.
3. Age of stand I n no case has litter-fall been followed through a generation in an individual stand, so that all studies of age effects have been based on diverse stands of different ages. The results of such studies are also rather diverse. For example, Danckelmann (1887b) found litter-fall in Fagus silvatica forests on good soils increased about 20% between 30 and 90 years, after which a slight decline was manifested, also evident in Hartig’s data for stands aged 80 to 120 years (cited by Ebermayer, 1876). On the other hand Ebermayer (1876) reported a trifling decline in litter-fall from 30 years on, and Moller (1945) found that standing crop of leaves varies rather little between young (31-60 years), medium (61-119 years) and old (120-200 years) forests, the crops averaging 2.8, 2.5 and 2.7 t/ha respectively. I n the case of Pinus silvestris Danckelmann (1887a) reported a very slight decline in litter-fall from age 30 on, while data from Voronezh in the U.S.S.R. (compiled by Sonn, 1960) showed a more striking drop, from 2.5 t/ha at age 20 to 1.3 t/ha at age 100. Ebermayer (1876) however recorded litter-falls of 2.9, 3.0 and 3.6 t/ha at ages 25-50,50-75 and 75-100 years respectively. For Picea abies Danckelmann (1887b) found maximum litter-fall to occur in middle age (60-80 years), while Ebermayer (1876) observed a steady decline from 4.5 t/ha in stands less than 30 years old to 2.8 t/ha in stands over 90 years old. If all the above-mentioned European data are graphed together and medians taken for successive intervals, little variation in litter-fall is evident from 30 to more than 100 years of age. It would appear that there is no inherent tendency toward higher or lower litter-fall with increasing age, once the canopy becomes closed, but that environmental conditions (including biological agents such as insects or fungi) exert a decisive influence. One additional Australian case may be of interest, in which Eucalyptus regnans stands of 25 years (height 27 m, density 1013 t/ha), 55 years (43 m, 217 t/ha) and circa 200 years (76 m, 47 t/ha) were examined by Ashton (private communication). Total litter-fall amounted to 6.1,
142
J. ROGER BRAY AND EVILLE GORHAM
7.2 and 7.2 t/ha for these three ages, and leaf litter to 3.2, 3.7 and 3.7 t/ha. Litter-fall was thus the same under the 55- and 200-year forests, despite a more than four-fold difference in density. However, undergrowth litter contributed about a quarter of the total litter collected beneath the 200-year forest and only about a tenth of that beneath the 55-year stand.
VI. STANDING CROP OF LEAVES A. SEASONAL CHANGES -INTRINSIC Olsen (1948) found no consistent dry weight change in leaves of Fagus silvatica after the rapid increase accompanying foliage maturation in May. The terminal value for yellow leaves prior t o defoliation was a trifle low, but cannot be specified accurately from his graph. Mitchell (1936) reported rather marked increases in leaf dry weight of six eastern American Angiosperm trees until the beginning of July (and in the two Quercus species until the beginning of August). Carya (Hicoria) ovata leaves in full autumn color weighed only a littlk less than green leaves sampled a month before. Tamm (1955) observed a spring phase of rapid dry weight increase in needles of Swedish Pinus silvestris and Picea abies, followed by a dry weight loss of about 20% in June and July. Viro (1955)sampled different age groups of needles of the same species in Finland during August, and found the dry weight of 1000 Pinus silvestris needles to be 28.6 g in the first year, 28.9 g in the second, 29.5 g in the third, and 34.4 g in older needles ranging up to eight years in age. For Picea abies needles the correspondingweights were 3.51,4-76,4*58and 5.02 g. Weight changes upon and immediately prior to abscission have been investigated by Viro (1955) in a comparison of dry weights of 1000 green leaves or needles collected in August with dry weights of 1000 yellow leaves or needles collected partly from the tree and partly from the ground at the end of September. Weight loss associated with yellowing averaged 21% (range 19 to 23%) for the deciduous Angiosperms Betula (pubescens and verrucosa), Populus tremula, Alnus incana and Salix caprea. If yellow Pinus silvestris needles are compared with needles older than three years, the yellow ones weigh 44% less. For Picea abies the difference is 39%. However, it cannot be assumed that all yellow needles are more than three years old. If yellow and three-year needles are compared, the weight loss on yellowing would appear to be only 34% for both Pinus and Picea. Such a weight loss would still be very high, about one-third of the total dry matter. A much lower difference between brownish and green Picea pungens needles was observed at Minneapolis, U.S.A., on 29 May 1963. Sixty-eight brownish needles were
LITTER PRODUCTION I N FORESTS OF THE WORLD
143
carefully plucked and trimmed along with the same number of immediately adjacent green needles, and a dry weight loss of only 13% was associated with browning. However, these brown needles were not quike ready to fall, for they required a distinct tug with forceps to pluck them. It was also apparent in this case that many needles remained long after abscission upon the branches beneath, where they had become trapped when falling. Presumably considerable weight loss might take place before such needles reached a litter collector. No data could be found for dry weight changes associated with abscission of Warm Temperate or Equatorial tree leaves. However, in 1962, leaflets were sampled from a small leguminous tree, Tamarindus indica, growing in the greenhouse of the Botany Department at the University of Toronto. This tree has compound leaves with from twenty to twenty-six opposite leaflets which yellow and drop off separately. Collections were made of leaflet pairs in which one leaflet was yellow, possessed a well-formed abscission layer, and dropped when lightly touched; while the opposite leaflet was green, healthy and fimly attached. Leaflets were washed with detergent to remove dust and other contaminants, and oven-dried at 80°C for 12h. The results of four leaflet collections from 2 March to 27 April showed the weight of yellow leaflets to vary from 77 to 84% of that of green leaflets, with a mean value of 81%. There was a slight tendency for the relative weight of the yellow leaflets to decrease as the season advanced and solar radiation and greenhouse temperature increased. On average, the Tamarindzls leaves appeared to lose nearly one-fifth of their dry matter before falling. I n another test on 23 May 1963, leaves were collected from a Ficus elastica tree growing in the greenhouse of the Botany Department at the University of Minnesota. A very few of the leaves were yellow, and fell when touched. Ten of these were collected along with immediately adjacent green and healthy leaves of closely similar size. Four 21 mm leaf discs were cut with a cork borer at random (but excluding the midrib) from each pair of washed leaves. The green and yellow leaves of each adjacent pair were superimposed so that disc locations would be the same, and two discs were cut with the green leaf on top, and two with the yellow leaf on top. Discs were then oven-dried a t 80' C overnight. The weight of the yellow discs was 81% of the weight of the green discs, indicating (as in the case of Tamarindus) that Ficus leaves lose nearly one-fifth of their dry matter just prior to abscission. It is interesting that results are identical for two leaves of such very different type, the leguminous leaves being small and rather delicate, the fig leaves large, leathqry and with a waxy surface.
144
J . ROGER BRAY AND EVILLE GORHAM
B. SEASONAL CHANGES - EXTRINSIC Estimates of the percentage utilization of attached leaves of forest trees by primary consumers range from 5.9% for an Acer saccharum Betula lutea - Fagus grandifolia swamp forest to 10.6y0 for an upland Quercus forest (Bray, 1964). The mean of leaf co&.umption values in Lindquist (1938), Rothacher et al. (1954) and Bray is 7.5%. The rate of consumption, decomposition and respiration occurring in leaves immediately after leaf-fall has seldom been studied. Lindquist (1938) estimated that 15% of Fraxinus leaf litter and 10% of Ulmus leaf litter were eaten by earthworms within 1 week after completion of leaf-fall. Loss of weight by respiration may also be high, especially before the leaf becomes desiccated. Studies of weight loss with various techniques of litter collection are badly needed, since such weight loss may be higher than is usually realized, especially when collections are made from the ground. There, leaves are subject to animal consumption, and also, if they remain moist, to microbial decay. Bocock et al. (1960) found that Quercus petraea leaves on a highly acid moder humus layer lost only about 10% of their dry weight in two months. The loss was about 13% on a faintly acid mull. Leaves of Fraxinus excelsior, much more susceptible to decay, lost about 26% of their dry weight in one month on the moder and about 43% on the mull. On the mull earthworms removed many whole Fraxinus leaflets from the nylon nets in which they were held. Lunt (1935) observed that in 7 weeks after leaf-fall the dry weight loss of some eastern North American Angiosperm tree leaves ranged from 3 to 12%, being low for Quercus alba and Fagus grandifolia, and high for Acer rubrum and Cornus jiorida. Earthworms were excluded from the samples by the fine cloth mesh beneath the flat boxes in which the leaves were placed.
c. MAGNITUDE
OF LEAF CROPS
Table XIX shows weights of all attached leaves in various forests, collections being made during the period of maturity but preceding the phase of defoliation. Data are on an annual production basis, to allow comparison of Angiosperms and Gymnosperms. The magnitude of these values for yearly leaf production is similar to that of the cold temperate leaf litter data in Table IV, but variability in site conditions, plant populations and growing season climate makes direct comparison dificult. I n view of the extrinsic and intrinsic losses between the period of petiole attachment and of collection in litter traps, it is likely that the leaf crop values in Table XIX are somewhat higher than litter values for the same community. Direct studies of leaf production and leaf litter within one forest are needed.
TABLEXIX Dry Weight of Xtunding Crops of Leaves on an Annual Production Basis* Authority
Location
Lat. Long. ~~
Bartholomew et al., 1953
Congo, Yangambi
Jacobs, 1936 Burger, 1947 Moller, 1945 Burger, 1947 Zemljanickii, 1954 Ovington, 1962 Potts, 1939 Rothacher et al., 1954
Southern Australia Switzerland, Adlisberg Denmark Switzerland, Winterthur U.S.S.R., Zavetnoe and Kamyshin U.S.S.R. U.S.A., Saugus, Mass. U.S.A., Tennessee
Ovington, 1962 Bray, unpublished
U.S.A., Bethel, Minn. U.S.A., Bethel, Minn.
U.S.A., San Dimas Forest, California Tadaki and Shidei, 1960 Japan Switzerland, Aarburg Burger, 1940 Denmark Mhller, 1945 Boysen-Jensent Denmark Denmark Tadaki and Shidei, 1960 Japan Denmark Mhller, 1945 Jokela and Yliinen, 1956 Finland Ovington, 1962 N. Sweden Ovington, 1962 U.S.S.R.
Kittredge, 1944
1N
56N 47N 47N 43N 45N 46N
Plant community
Age (yr)
~
6 24E Musanga cecropioides pioneer forest Musanga cecropioides pioneer forest 8 Musanga cecropioides pioneer forest 17-18 Evergreen Eucalyptus giganteu forest Quercus robur 13 50 12E Quercus robur 9E Quercus robur - Fagus silvatica forest 65 43E Quercus robur - Fraxinus pennsylvanica 17 shelterbelt Quercus forest 22-200 71W Quercus forest Quercus forest, heavily cut 15 yrs before sampling 93W Quercus forest 57 93W Quercus ellipsoidalis - Q. alba closed forest 62 Quercus elliwoidalis open forest 43 Quercus ellipsoidalis -Q. macrocarpa savannah 60 Quercus chrysolepis 55
35N 136E Quercus mongolica v. grosseserrata 47N 8E Fagus silvatica Fagus silvatica Fagus silvatica Fraxinus excelsior 35N 136E Fraxinus rnandshurica Betula verruco8a Betula verruwsa, B e t d a alba Betula verrucosa Betula vemucosa
* All oven-dried except the U.S.S.R. t From Tadaki and Shidei (1960).
(air-dried) and possibly the Finnish semplee.
80 40
25 26 20-40
Leaf crop (metric tonsblur) 5.6 5.4 6.4 4.4 5.3 4.0 3.1 3.0
3.1 2-6 3.8
3.5 5.2 2-1 0.8 4.1 2.7
3.2
2-7 3-1 2-7 2.2 3.3 2.0 2-7 3.6
TABLEXIX - continued Authority
Ovington and Madgwick, 1959 Ovington, 1962 Tadaki et al., 1961 Tadaki and Shidei, 1960 Bray and Dudkiewicz, 1963 Bray and Dudkiewicz, 1963 Satoo et al., 1956 Auten, 1941 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Ovington, 1957
Location
Lat. Long.
Plant community
England, Peterborough
53N
Japan Japan Japan U.S.A., Itasca, Minn.
Betula maximowicziana 43N 144E Betula platyphylla 35N 136E Betula ermanii 47N 95W Populw tremuloidee closed forest
Canada, Dorset, Ontario
45N
Japan, Hokkaido U.S.A., Illinois or Indiana
43N 40N
Japan Japan Japan Japan England, Brandon
35N 35N 35N 35N 52N
Kittredge, 1944
U.S.A., Stanislaus National Forest, California Maruyama and Satoo, 1953 Japan, Makibori, Iwate Mork, 1942 Norway, Hirkjolen Burger* Switzerland Shibamoto* Japan
38N 40N 62N
OW Betula verrucosa
79W Populua tremuloidea - Populua grandidentaka open forest 143E Populua davidiana: 88W Robinia pseudacacia on old field Bassafras albidum on old field 136E Alnus hirsuta 136E A l n w hirsukz v. sibirica 136E S a l k gracilistyla 136E Salix vulpina 1E Pinua dveatris, plantation Pin- silvestris, natural regeneration P i n w nigra, plantation P i n w ponderosa 120W 88W Pinua densiJora forest 10E Picea abies Larix decidua Larix leptolepis
*From Tadaki and Shidei (1960).
Age
(Yd
24-55
Leaf crop (metric tonslhalvr) 1.7
41
2.2 1.2 2.4 3.8
39
1.6
25-40 9 12
2.2 2.9 2.8 2.6 2.6 3.5 2-3 2.9 3.9 3.7 2.0
10
3-55 11-14 31 65-69 40
1.7
0.8 2.6 3.3
LITTER PRODUCTION IN FORESTS OF THE -WORLD
147
The mean leaf crop in t/ha/yr for closed canopy Angiosperm forests in Table XIX is 3.7 for eleven Quercus sites, 3.0 for three Fagus sites, 2.9 for two Salix sites, 2.6 for two Alnus sites, 2.5 for two Fraxinus sites, 2-5 for three Populus sites, and 2-4 for eight Betula sites. The high values for Quercus sites, which range from 2.6 to 5.3 t/ha and include four studies with values of 4-0 t/ha or more, are noteworthy. The Quercus leaf is usually thick and leathery, with a high lignin content (see Handley, 1954, Table XII). It is possible that Quercus forests are among the highest pPoducers of leaf litter within the Temperate regions; and the thick soil litter layers frequently found in Quercus forests may be related to high production of leaves as well as to the slow rate of leaf decay of many species in this genus. Some of the Betula and Populus data &retaken from more northerly areas of the Temperate zone, and are not directly comparable with the Quercus values. Leaf crops of Gymnosperms in Table XIX are similar to those of Angiosperms, with means in t/ha/yr of 2.8 for five Pinus sites and of 3.0 for two Larix sites. Of the nine Angiosperm and Gymnosperm genera with two or more sites, seven genera, including both Gymnosperm genera, have leaf crops between 2.5 and 3-0 t/ha/yr. Mean Angiosperm leaf production by genera is 2.8 t/ha/yr which is similar to the Gymnosperm mean of 2.9 t/ha/yr.
VII. LEAFLITTERAS AN INDEXTO NET PRODUCTION Although leaf litter represents an amount somewhat less than leaf production, owing to intrinsic and extrinsic weight losses prior to and probably also following abscission, it may still be useful as a guide to minimum levels of total net production. There is a logarithmic relationship between the foliage weight of some needle-leaved and a few broadleaved trees and tree stem diameter (Kittredge, 1944; Cable, 1958; Satoo, 1962). It is doubtful if this relationship is of much use in predicting net total production since (1) the constants in the regression equation obtained for a given stand will not, because of varying modes of competition, necessarily apply to other stands of the same species (Satoo, 1962) and (2) the relationship does not apply over the entire life-span of a tree since it is common for many Gymnosperms, including Pinus banksiana and P. contorta, to have a reduced, scraggly, broomshaped crown in later years, which is much smaller than the crown in the earlier part of the life span. Cooper (1960) demonstrated a linear relationship between needle air-dry weight and growth of stem basal area from stump sections in two plots of young (30 yr and 49 yr) Pinus ponderosa. There was no statistical difference in the regression equation for the two plots. Other studies of foliage in relation t o net production are desirable to determine whether a general regression equation can be
TABLEX X Net Leaf Production in Relation to Net Non-leaf Production* ~~
~
Authority
Species
Total
Leaf
Stem
(metric tons /ha/yr) Polster, 1950 Ovington, 1957 Ehwald, 1957 (data of Zhmerle) Polster, 1950 Moller, 1945 Ehwald, 1957 (data of Zimmerle) Polster, 1950 Polster, 1950 Polster, 1950 Moller et al., 1954 Ehwald, 1957 (data of Dieterich) Ovington and Madgwick, 1959 Polster, 1950 Ovington et al.. 1963 Polster, 1950 Satoo et al., 1956 Bray and Dudkiewicz, 1963 Moller, 1945 Nye, 1961 Bartholomew et al., 1953 Means
Below ground
Pinua silvestris Pinus silvestris Pinua mXvestria
9.4 12.4 8.8
1.5 3.3 3.0
6.3 7.2 4.6
( 1.6) 1.9 1.2
Picea abies Picea abies Picea abies
14.2 15.6 14.8
2.1 2.7 3.7
9.7 (10.4) 9.0
(2.4) (2.5) 2.1
Pseudotsuga rnenziesii Larix europaea Fagus silvatica Fagus silvatica Fagus silvatica
17.5 14.2 14.2 11.4 12.6
2.7 5.6 3.2 2.5 3.5
11-9 6.2 8.6 7.4 7.3
(2-9) (2.4) (2.4) 1.5 1.8
Betula verrucosa Betula verrucosa Quercus borealis Quercus robur Populua davidiana Populus trernuloidee Fraxinus excelsior Equatorial forest, Ghana Equatorial forest, Congo 7 evergreen Gymnosperms 10 deciduous Angiosperms 18 cold temperate forests 2 equatorial forests
9.0 8.6 9.1 10.4 7.8 10.9 10.9 24.3 31-5 13.2 10.5 11.7 27.9
1.7 2.0 3.5 2.4 2.2 3.8 2.7 7.0 9.5 2.7 2.8 2.9 8.3
5.1 5.2 4.1 6.3 4.3 5.3 6-7 14.7 19.2 8.4 6-0 7.0 16.9
2.2 (1.4) (1.5) (1.7) (1.3) (1.8) 1.5 2.6 2.8 2.1 1.7 1-9 2.7
* Figures in brackets were estimated (see text).
LITTER PRODUCTION IN FORESTS OF THE WORLD
149
derived which is applicable within species or taxonomic groups. It is likely that amount of foliage will be more easily correlated with current growth than with mean growth over the lifetime of a tree or forest. Table X X lists strdies from which leaf production can be compared to non-lea€and total net production. If below-ground production figures were lacking, a conversion factor of 0.2 times above-ground production was employed to estimate them (Bray, 1963). A value of 12.9 t/ha for stem plus below-ground production in Picea abies (Moller, 1945) was separated into 10.4 and 2.5.t/ha respectively by using the average ratio of stem to below-ground production in six Cool Temperate stands for which observed values were available. (The stand of Betula verrucosa on deep peat, sampled by Ovington and Madgwick (1959), was excluded because it fielded a widely aberrant ratio.) It is clear from Table XX that stem production (4.3 to 19-2 t/ha/yr) exceeds leaf production (1.5 to 9.5 t/ha/yr), which in turn exceeds root production (1.2 to 2.9 t/ha/yr). Total annual production ranges from 7.8 t/ha in a Japanese stand of Populm davidiana to 31.5 t/ha in a Congo forest. A summary of relative litter production by climatic zones together with various indexes of net total production is shown in Table XXI, with Arctic-Alpinevalues being taken as unity in the f i s t three columns, and Cold Temperate values in the last three columns. Bole production was estimated from data in Paterson (1956) by determining the range of C W (climate-vegetation-productivity) indexes for the climatic areas of the stands summarized in Table IV from Tables 16, 17, 18, 19, 20 and 21 of Paterson as follows: Arctic-Alpine,, CVP: 25-100; Cold Temperate, CVP: 100-500; Warm Temperate, CVP: 500-ca 3 000; Equatorial, CVP: 3 000-20 000. Mean bole production in m3/ha calculated from Table XXII of Paterson was 2.0 for Arctic-Alpine, 5.5 for Cold Temperate, 10-3 for Warm Temperate and 14.0 for Equatorial forest areas. Relative bole production for the four climatic areas was 1 to 2.7 to 5-1 to 7.0, which was similar to the ratios for leaf litter of 1 to 3.6 to 5.1 to 9.7, although the relative range for bole production from Arctic-Alpine to Equatorial forest was less than the range for leaf litter production. The other relative production values summarized in Table XXI are for Cold Temperate and Equatorial forest only, and show a range of from 2.3 to 3.0 (mean 2.6) for Equatorial forest over Cold Temperate values. Litter production of Equatorial forest varies from 2.7 (leaf litter) to 3.1 (total litter) times Cold Temperate litter production, which indicated that the use of litter data t o predict total production would slightly overestimate the differencein production between Cold Temperate and Equatorial forest. The ratios in Tables XX and XXI indicate that Equatorial forest is around two to three times as productive as Cold Temperate forest ; that Warm Temperate forest productivity F
C.E.R.
TABLEXXI Relative Litter, Bole and Total Organic Matter Production in Four Major Climatic Zones Total litter (from Table XI)
Leaf litter Bole production Total production Total broad-leaved Total needle-leaved tree production tree production (from (from (from (from Becking, 1962) (from Becking, 1962) Table XI) Paterson, 1956) Table XX)
Arctic-alpine*
1.o
1.0
1.0
-
-
-
Cold temperate?
3.5
3.6
2.7
1.0
1*o
1.0
Warm temperate
5.5
5.1
5.1
-
-
-
10.9
9.7
7.0
2.3
3.0
2.4
Equatorial
* Taken as unity in the firat three columns.
7 Taken aB unity in the last three columns.
151
LITTER PRODUCTION IN FORESTS OF T E E WORLD
is nearer t o Cold Temperate than to Equatorial forest productivity, and that Arctic-Alpine forest is less than half as productive as Cold Temperate forest.
TABLEXXII Ratios of Total, Non-leaf and Stem Production to Leaf Production Total Leaf
~~
Non-leaf Leaf
Stem Leaf ~
Cool temperate evergreen Gymnosperms Cool temperate deciduous Angiosperms Equatorial forest
4.9
3.9
3.1
3.7 3.3
2.7
2.1 2.0
2.4
Ratios of total net production, non-leaf production and stem production to leaf-production are given in Table XXII, for evergreen Gymnosperms and deciduous Angiosperms in the Cool Temperate zone and for Equatorial forests. It is evident that the Gymnosperms exhibit the highest ratios, and the Equatorial forests the lowest. The apparent lower efficiency of tropical tree leaves in producing non-leaf material probably reflects a high rate of respiration (relative to rate of photosynthesis) under higher tropical temperatures. The higher efficiency of temperate Gymnosperm as compared with Angiosperm leaves in producing non-leaf material may be owing to their much longer period (more than two years) of contribution to net production. The significance of the ratios in Table XXII is di%cult to assess because of the small number of studies available. Further productivity research is needed, especiallyin tropical and warm temperate forests, and until such work is done our estimates of net forest production cannot be securely founded. If the ratios of non-leaf to leaf production are approximately correct, then a comparison of them shows that leaf litter cannot be employed directly as an index to net forest production, since evergreen Gymnosperm leaves produce annually over 40 % more non-leaf material than do deciduous Angiosperm leaves, and over 60% more than Equatorial forest leaves. The use of leaf litter values as production indices would therefore greatly overestimate Equatorial forest production and underestimate production by evergreen Gymnosperms. The Cool Temperate Gymnosperms are about 25% more productive than the Angiosperms (13.2 t/ha as against 10.5 t/ha in Table XX). The evergreen nature of the Gymnosperm trees (allowing photosynthesis whenever temperatures are suitable), and the great weight of canopy carried (with several years’ needles present), are presumably responsible for their comparatively high levels of production. Ovington (1956) has
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found that in English forest plantations Gymnosperms may be several times as productive as Angiosperms on the same sites. I n a general comparison over wide areas, however, the tendency of Angiosperms to occur on better soils than Gymnosperms may lessen the differences in production brought about by differences in canopy weight and duration. REFEBENCES Aaltonen, V. T. (1948). “Boden und Wald”, 457 pp. Berlin and Hamburg: Paul Parey. Alway, F. J., Methley, W. J. and Younge, 0. R. (1933).Soil Sci. 36, 399-407. Distribution of volatile matter, lime and nitrogen among litter, duff, and leaf mold under different forest types. Alway, F. J. and Zon, R. (1930).J. For. 28, 715-727. Quantity and nutrient contents of pine leaf litter. Andersson, S. 0. and Enander, J. (1948). Svenska SkogsvF&en. Tidakr. 46, 265-270. Om produktionen av lovforna och dennas sammansiittning i ett mellansvenskt aspbesthd. AndrB, P. (1947). Svenska SkogmForen. Tidskr. 45, 122-131. Bamkens och mossornasfornaproduktion i ett barrskogsbest&nd. Anonymous (1932). Bull. N.H. agric. Exp. Sta. no. 262. Formation of forest soils: rate of deposition of litter. Anonymous (1960).Rep. cent. St. F o r . Exp. Sta., p. 12. Auten. J. T. (1941). Tech. Notes cent. St. For. Exp. Sta. 32, 9 pp. Black locust, pines and sassafras as builders of forest soil. Bartholomew, W. V., Meyer, J. and Laudelot, H. (1953).Publ. INEAC Ser. Sci., 57, 27 pp. Mineral nutrient immobilization under forest and grass fallow in the Yangambi (BelgianCongo) region. Becking, J. H. (1962).I n “Die Stoffproduktion der Pflanzendecke” (ed.H. Lieth), pp. 128-131. Stuttgart: Gustav Fischer Verlag. Ein Vergleich der Holzproduktion im gemiissigten und im tropischen Klima. Black, J. N. (1956). Arch.. Met. Wien, Ser. B, 7 , 165-189. The distribution of solar radiation over the earth’s surface. Blow, F. E. (1955).J. For. 53, 190-195. Quantity and hydrologic characteristics of litter under upland oak forests in emtern Tennessee. Bocock, K. L., Gilbert, O., Capstick, C. K., Twinn, D. C., Waid, J. S. and Woodman, M. J. (1960).J. Soil Sci. 11, 1-9. Changes in leaf litter when placed on the surface of soils with contrasting humus types. Bohrnerle, K. (1906). “Die Streuvemuche im grossen Fohrenwalde”. 22 pp. Vienna: W.Frick. Bonnevie-Svendsen, C. and Gjems, 0. (1957).Medd. Norske Skogsfors~ksv.48, 111-174. Amount and chemical composition of the litter from larch, beech, Norway spruce and Scots pine stands and its effect on the soil. Bornebusch, C. H. (1937). pOr8tl. Fors0bv. Danm. 14, 173-176. Iagttagelser over rpldgranens naalefald. Boysen-Jensen, P. (1930).Forstl. Forsoksv. Danm. 10, 365-391. Undersogelser over Stofproduktionen i yngre Bevoksningeraf Ask og Bog. 11. Brauns, F. E. and Brauns, D. A. (1960). “The Chemistry of Lignin”, Suppl. Vol., 804 pp. New York and London: Academic Press.
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Bray, J. R. (1964). Ecology 45, 165-167. Primary consumption in three forest canopies. Bray, J. R. (1963). Canad. J . Bot. 41, 66-72. Root production and the estimation of net productivity. Bray, J. R. and Dudkiewicz, L. A. (1963). Bull. Torrey bot. Cl. 90, 298-308. The composition, biomass and productivity of two Populus forests. Broadfoot, W. M. and Pierre, W. H. (1939). Soil Sci. 48, 329-348. Forest soil studies: I. Relation of rate.of decomposition of tree leaves to their acid-base balance and other chemical properties. Burger, H. (1925). 2. Forst- u. Jagdw. 57, 473-482. Die Transpiration unserer Waldbiiume. Burger, H. (1940). Mitt. Schweiz. ZentAnst. forstl. V e r a u c h . 21, 307-348. Holz, Blattmenge und Zuwachs. IV. Ein 80 j h i g e r Buchenbestand. Burger, H. (1947). Mitt. Schweiz. ZentAnet. forstl. V e r s u c h . 25, 211-279. Holz, Blattmenge und Zuwachs. VIII. Die Eiche. Cable, D. R. (1958). Forest Sci. 4, 45-49. Estimating surface area of ponderosa pine foliage in central Arizona. Chandler, R. F., Jr. (1941). J . Amer; SOC.Agron. 33, 859-871. The amount and mineral nutrient content of freshly fallen leaf litter in the hardwood forests of central New York. Chandler, R. F., Jr. (1944). Proc. Soil Sci. SOC.Amer. 8, 409-411. Amount and mineral nutrient content of freshly fallen needle litter of some north-eastern conifers. Claudot, M. (1956). FAO/SCMIEUI7-B. Influence de 1’Eucalyptussur l’evolution des sols au Maroc. (Mimeographed.) Coldwell, B. B. and DeLong, W. A. (1950). Sci. Agric. 30, 456-466. Studies of the composition of deciduous forest tree leaves before and after partial decomposition. Cooper, C. F. (1960). Ecol. Monogr. 30,129-164. Changes in vegetation, structure, and growth of south-westernpine forests since white settlement. Crosby, J. S. 1961. Tech. Pup. cent. St. For. Exp. Sta. 178, 10 pp. Litter-and-duff fuel in shortleaf pine stands in Southeast Missouri. Curtis, J. T. (1959). “The Vegetation of Wisconsin”, 657 pp. Madison, Wisconsin: University of Wisconsin Press. Danckelmann, B. (1887a). 2. Forst- u. Jagdw. 19, 457-466. Streuertragstafel fiir Kiefern bestlinde. Danckelmann, B. (1887b). 2. Forst- u. Jagdw. 19, 577-587. Streuertragstafel fiir Buchen- und Fichtenhochwaldungen. Dimock, E. J. (1958). Northw. Sci. 32, 19-29. Litter fall in a young stand of Douglas fir. Eberinayer, E. (1876). “Die gesamte Lehre der Waldstreu mit Rucksicht auf die chemische Statik des Waldbaues”, 116 pp. Berlin: Julius Springer. Ehwald, E. (1957). Dtsch. Akad. Landwirtschaftwiesenschaften Berlin. 6 , 1-56. ifber den Nlihrstoffkreislaufdes Waldes. Gaffron, H. (1946). I n “Currents in Biochemical Research” (ed.D. E. Green), pp. 25-48. New York: Interscience. Photosynthesis and the production of organic matter on earth. Glesinger, E. (1949). “The Coming Age of Wood”, 279 pp. New York: Simon and Schuster. Handley, W. R. C. (1954). Bull. For. Corm. London, 23, 115 pp. Mull and mor formation in relation to forest soils.
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Hatch, A. B. (1955). LeafE. For. Bur., Canberra 70, 18 pp. The influence of plant litter on the jarrah forest soils of the Dwellingup region, Western Australia. Hesselman, H. (1925). Medd. Skogsforsoksanst 22, 169-552. Studier over barrskogens humustacke, dess egenskaper och beroende av skogsvhrden. Heyward, F. and Barnette, R. M. (1936). Bull. Fla. agric. Exp. Sta. 302, 27 pp. Field chmacteristics and partial chemical analyses of the humus layer of longleaf pine forest soils. Jacobs, M. R. (1936). Commonwe&h Por. Bur. Bull. (Canberra, Australia) 18, 78 pp. The primary and secondary leaf-bearing systems of the eucalypts and their silvicultural significance. J&6, Z. (1958). Erd4szettudodnyi Koslednyek, Sopron 1, 151-162. Alommennyis6gek a magyar erdokben. Jenny, H., Ge~sel,S. P. and Bingham, F. T. (1949). Soil Sci. 68,419-432. Comparative study of decompositionrates of organic matter in temperate and tropical regions. Joffe, J. (1949). “Pedology”, 662 pp. New Brunawick, N.J.: Pedology Publications. Jokela, E. and Yliinen, J. (1956). Metsut. Aikakausl. 73, 131-132. Koivikoiden lehtkadon miiliriistli. Kendrick, W. B. (1959). C a d . J . Bot. 37,907-912. The time factor in the decomposition of coniferous leaf litter. Kittredge, J. (1940). J. For. 38, 729-731. A comparison of forest floors from plantations of the same age and environment. Kittredge, J. (1944). J . For. 42, 905-912. Estimation of the amount of foliage of trees and shrubs. Knudsen, F. and Mauritz-Hansson, H. (1939). Svenska SkogsvForen. Tidskr. 37, 339-347. Om produktionen av lovforna och dennaa sammrtnslittning i ett mellansvenskt bj orkbesthd. Krutzsch. H. (1869). Tharandt.forstl. Jb. 19, 19S227. Untersuchungen iiber die Waldstreu. Lespeyres (1898). 2. Forst- u. Jagdw. 30, 521-537. Der Einfluss der Streuniitzung auf den Holzwuchs in den Kiefernbestlinden des nordostdeutschen Flachlrtndes. Laudelot, H. and Meyer, J. (1954). Act@ et Comptes Rendua du V eCongrbs International de la Science du Sol 2, 267-272. Les cycles d’6lBments mineraux et de mrttihre orgaaique en for6t Bquatorialecongolake. Levina, V. I. (1960). Bot. Zh. 45, 41&423 (cited in For. Abstr. 21, 532, 1960. Determination of the amount of annual litter fall in two types of pine forest on the Kola Peninsula). Lindberg. S. and Norming, H. (1943). Suenska SkogsvForen. TicEskr. 41, 353-360. Om produktionen av barrforna och dennas sammrtnslittning i ett granbesthd invid Stockholm. Lindquiat, B. (1938). Actaphyzogeogr.Suec. 10,273 pp. Dalby Soderskog. Lunt, H. A. (1935). J . For. 33, 607-609. Effect of weathering upon dry matter and composition of hardwood leaves. Lunt, H. A. (1951). Proc. Soil Sci. SOC.Amer. 15, 381-390. Liming and twenty years of litter raking and burning under red (and white) pine. Lutz, H. J. and Chandler, R. F., Jr. (1946) “Forest Soils”, 514 pp. New York: John Wiley. Maruyarna, I. and Satoo, T. (1953). Bull. For. Exp. Sh. Meguro 65, 1-10. Estimation of the amount of foliage of trees and stands. Report 1. On the Akamatu of Iwate District. Mayer-Krapoll, H. (1956). “The Use of Commercial Fertilizers -particularly
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Nitrogen - in Forestry”, 11 1 pp. Translated and published by Nitrogen Div., Allied &em. and Dye Corp., New York. Melin, E. (1930). Ecology 11, 72-101. Biological decomposition of some types of litter from North American forests. Metz, L. J. (1952). Proc. Soil Sci. SOC.Amer. 16, 38-41. Weight and nitrogen and calcium content of the annual litter fall of forests in the South Carolina Piedmont. Mikola, P. (1954). Commun. Inst. for. Finl. 43, 1-50. Kokeellisiatutkimuksia metsiikarikkeiden hajaatumisnopeudesta. Miller, R. B. and Hurst, F. B. (1957). N.Z. For. Res. Notes 8, 14 pp. The quantity and nutrient content of hard beech litter. Mitchell, H. L. (1936). Black Rock For. Pap. 1, 30-44. Trends in the nitrogen, phosphorus, potassium and calcium content of the leaves of some forest trees during the growing season. Moller, C. M. (1945). Forstl. Forseksv. Danm. 17, 287 pp. Untersuchungen iiber Laubmenge, Stoffverlust and Stoffproduktion des Waldes. Moller, C. M. (1947). J . For. 45, 393-404. The effect of thinning, age and site on foliage, increment and loss of dry matter. Moller, C. M., Miiller, D. and Nielsen, J. (1954). F o r d . Forsokew. Danm. 21, 273-301. Respiration in stem and branches of beech. Mork, E. (1942). Me&. Norske Skogfors~ksv.29, 297-365. Om strafallet i v b e skoger. Miiller, P. E. (1887). “Studien uber die natiirlichen Humusformen und deren Einwirkung auf Vegetation und Boden”, 324 pp. Berlin: Julius Springer. Navarro de Andrade, E. (1941). J . Hered. 32, 215-220, and 240. T h e eucalyptus in Brazil. Nye, P. H. (1961). Plant & Soil 8, 333-346. Organic matter and nutrient cycles under moist tropical forest. Nykvist, N. (1963). Stud& for. Suec. 3, 31 pp. Leaching and decomposition of water-solubleorganic subst?nces from different types of leaf and needle litter. Ogawa, H., Yoda, K. and Kira, T. (1961). Nature and Life in8.E. A& 1,21-157. A preliminary survey of thle vegetation of Thailand. Ohmasa, M. and Mori, K. (1937). Bull. For. Exp. Sta. Tokyo-Fu 3, 39-101. The amount of fall and decompositionof the leaf litter of the forest trees of Japan. Olsen, C. (1948). C.R. Lab. Carlsberg, Ser. Chim., 26, 197-230. T h e mineral, nitrogen and sugar content of beech leaves and beech leaf sap at various times. Ovington, J. D. (1956). New Phytol. 55, 289-304. The form, weights and productivity of tree species grown in close stands. Ovkgton, J. D. (1957.)Ann. Bot., Lond. N.S. 21, 287-314, Dry matter production by Pinus sylvestris L. Ovington, J. D. (1962). Adv. Ecol. Res. 1, 103-192. Quantitative ecology and the woodland ecosystem concept. Ovington, J. D., Heitkamp, D. and Lawrence, D. B. (1963). Ecology 44, 52-63. Plant biomass and productivity of prairie, savanna, oakwood and maize field ecosystemsin central Minnesota. Ovington, J. D. and Madgwick, H. A. I. (1959). Plant & Soil 10, 271-283. The growth and composition of natural stands of birch. 1. Dry matter production. Ovington, J. D. and Pearsall, W. H. (1956). Oikos 7, 202-205. Production ecology 11.Estimates of average production by trees. Owen, T. H. (1954). Forestry 27, 7-15. Observations on the monthly litter-fall and nutrient content of Sitka spruce litter. Paterson. S. S. (1956). “The Forest Area of the World and its Potential Pro-
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ductivity”, 216 pp. and map. Sweden: Dept. of Geography, the Royal University of Goteborg. Patterson, S. S. (1961). Medd. SkogsforsknInst. Stockh. 50, 1-145. Introduction to phyochorology of Norden. Perina, V. and Vintrova, E. (1958). Sborn. Esl. Akad. zeme‘d. (Lesn.)4, 673-688. The effect of fallen pine-needles on the humus conditions of $he pinewoods on the Pleistocene sands (Engl. summary). Pirie, N. W. (1953). Chem. Ind. Lond., No. 19, 442-445. The efficient use of sunlight for food production. Pirie, N. W. (1958). Sci. News, Harmondsulorth 49, 17-38. Unconventional production of foodstuffs. Pirie, N. W. (1961). Econ. Bot. 15, 302-310. Progress in biochemical engineering broadens our choice of crop plants. Pirie, N. W. (1962). J . R . stutiet. SOC.Ser. A. 125, 399-417. Future sources of food supply: scientific problems. Polster, H. (1950). “Die physiologischen Grundlagen der Stofferzeugung im Walde”, 96 pp. Munich :Bayerischer Landwirtschaftsverlag. Potts, S. F. (1939). J . For. 37, 922-923. A method for determining the quantity of foliage per acre of woodland. Remezov, N. P. and Bykova, L. N. (1953). Pochvovedenie 8, 28-41. (Cited in For. dbstr. 16, 334-335, 1955. Uptake and cycle of nitrogen and ash elements in aspen stands.) Richards, P. W. (1957). “The Tropical Rain Forest”, 450 pp. Cambridge Univ. Press. Rothacher, J. S., Blow, F. E. and Potts, S. M. (1954). J . For. 52, 169-173. Estimating the quantity of tree foliage in oak stands in the Tennessee Valley. Satoo, T. (1962). J . Jup. For. SOC.44, 267-272. Notes on Kittredge’s method of estimation of amount of leaves of forest stand. Satoo, T., Kunugi, R. and Kumekawa, A. (1956). Bull. Tokyo Univ. For. 52, 33-58. Materials for the studies of growth in stands. 3. Amount of leaves and production of wood in an aspen (Populua davidiana) second growth in Hokkaido. Scott, D. R. M. (1955). Yule Sch. For. Bull. 62, 73 pp. Amount and chemical composition of the organic matter contributed by overstory and understory vegetation to forest soil. Sims, I. H. (1932). J . For. 30, 90-91. Litter deposition and accumulation ,iathe pine-oak type of the Southern Appalachians. sjors, H. (1954). Actaphytogeogr.w e c . 34, 135 pp. SlBtterSngar i Grangiirde Finnmark. Smith, A. H. (1958). “The Mushroom Hunter’s Field Guide”, 197 pp. Ann Arbor: University of Michigan Press. SOM, S. W. (1960). “Der Einfluss des Waldes auf die Boden” (trans.P. Kundler), 166 pp. Jena: Gustav Fischer Verlag. Stoate, T. N. (1958). Rep. For. Dep. W . Austral. 25, 25. Silvicultural and soils research. A. Karri silviculture. Sviridova, L. K. (1960). Pochvovedenie 4, 68-73. (Trans.in Soviet Soil Sci. 1961, 401-405. Role of improvement cuttings in raising forest soil fertility.) Tadaki, Y . and Shidei, T. (1960). J . Jap. For. SOC.42, 427-434. Studies on productive structure of forest. 1. The seasonal variation of leaf amount and the dry matter production of deciduous sapling stand ( U l m w parviflora). Tadaki, Y . , Shidei, T., Sakasegawa, T. and Ogino, K. (1961). J . Jap. For. Sot.
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43,19-26. Studies on productive structure of forest. 2. Estimation of standing
crop and some analyses on productivity of young birch stand ( B e t h PktYPhYW. T a m , C. 0. (1955). M a . SkogsforsknInst.Stockh. 45, no. 5, 34 pp. Studies on forest nutrition I. Seasonal variation in the nutrient content of conifer needles. T a m , C. 0. (1958). In “Forest Fertilization, a New Era”, pp. 2-11. h e r . Potash. Inst. Handbook. Forest fertilization in Europe, its research and practices. Tarrant, R. F., Isaac, L. A. and Chandler, R. F., Jr. (1951). J . For. 49, 914-915. Observations on litter fall and foliage nutrient content of some Pacific Northwest tree species. Viro, P. J. (1955). Commun. Inst.for. Finl. 45, 65 pp. Investigations on forest litter. Walter, H. and Lieth, H. (1960). Klimadiagramm-Weltatlas. Jena: Gustav Fischer. Weck, J. (1955). “Forstliche Zuwachs-und Ertragskunde”, 160 pp. Radebeul and Berlin : Neumann Verlag. White, D. P. (1954). Proc. Soil Sci. SOC.Amer. 18, 326-330. Variation in the nitrogen, phosphorus and potassium contents of pine needles with season, crown position, and sample treatment. Wiedemann, E. (1951). “Ertragskundliche und waldbauliche Grundlagen der Forstwirtschaft”, 346 pp. Frankfurt-aml?lctinMain: J. D. Sauerlander’sVerlag. Will, G. M. (1959). N.Z. J . ugric. Rea. 2, 719-734. Nutrient return in litter and rainfall under some exotic conifer stands in New Zealand. Witkamp, M. and van der Drift, J. (1961). Plant &Soil 15,295-31 1. Breakdown of forest litter in relation to environmental factors. Wright, T. W. (1957). Forestry 30, 123-133. Some effects of thinning on the soil of a Norway spruce plantation. Zemljanickii, L. T. (1954). Pochwovedenie 12, 30-35. (Cited in For. Abstr. 16, 469, 1965. Quantity and ash composition of litter in artificial forest plantations in the zone of chestnut soils.)
F2
C.E.R.
.
J ROGER B R A Y
Grasslands Division. D.S.I.R., Palmerston North. New Zealand and E V I L L E GORHAM
Botany Department. University of Minnesota. Minneapolis. Minn., U .S.A . I. Introduction ........................................................ 101 I1. SourcesofData...................................................... 104 A. UnpublishedStudybyJ.R.Bray ................................... 104 B . WorldReview .................................................... 106 I11. Selection and Presentation of Data ..................................... 107 A Criteriafor Acceptance ............................................ 107 B . Arrangement ..................................................... 108 IV. Litter Components ................................................... 118 A Detailed Litter Separation ......................................... 118 B . Percentage of Non-Leaf Litter ...................................... 118 C Understory Litter ................................................ 119 D MineralMaterial .................................................. 121 E . OrganicMaterial.................................................. 125 V Factors Affecting Litter-Fall .......................................... 125 A. Evergreen Gymnosperm and Deciduous Angiosperms ................. 125 B Environment ..................................................... 127 C. Treatment ....................................................... 131 D . TheTimeFactor ................................................. 133 VI. StandingCropofLeaves.............................................. 142 A SeasonalChanges-Intrinsic ...................................... 142 B . Seasonal Changes - Extrinsic ....................................... 144 C . MagnitudeofLeafCrops ........................................... 144 VII . Leaf Litter as an Index to Net Production ............................... 147 References................................................................ 152
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I . INTRODUCTION The organic debris shed by forest vegetation upon the surface of the soil has long engaged attention . I n the past. branches and twigs were
t This study formed part of the authors’ research programmes while they were on the staff of the University of Toronto. Canada.
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used as fuel, and leaves as bedding for farm animals or as a soil treatment. I n Germany such utilization prompted concern over site degradation, and provided a stimulus for Ebermayer’s (1876) classic work on the production and chemical composition of forest litter. This study demonstrated conclusively the importance of litter-fall in the nutrient cycle of the forest, at the same time that its significance in soil development was being shown by Miiller’s (1887) pioneer investigation of the types of forest humus layer. More recent studies of the importance of litter-fall in the forest ecosystem have been reviewed by Lutz and Chandler (1946). I n the future, forest litter may assume additional significance. The current rapid increase in human population, with its consequent pressure on food supplies and accelerated depletion of non-renewable resources such as coal and oil, will eventually necessitate much fuller use of the world’s organic production (cf. Gaffron, 1946). To be thoroughly efficient such utilization must be mainly a t the level of green plants, the primary producers in the food web. It will also depend upon cheaper sources of energy and on great expansion of biochemical engineering, with current plant residues of all kinds serving as raw materials in addition to the present mainstays - agricultural crops, tree boles, and fossil plant deposits of coal and oil. Because much of the world’s land is best suited to the growth of trees, and wood will in any case remain a valuable raw material in its own right, forests will probably be a major source of materials for the new biochemical technology, particularly since mature stands can in certain circumstances be managed economically on a sustaining basis by selective felling. Moreover, forests utilize both light and growing season to a much greater degree than most agricultGa1 crops, especially if the trees arel evergreen. Total yields of forest dry matter compare favorably with those of farm crops, even without the constant cultivation and fertilization the latter receive (Weck, 1955 ;Ovington and Pearsall, 1956; Ovington, 1956). If forest production is to be used with maximum efficiency, the leaves and other debris should be utilized along with boles and slash, since they make up an important part of the total yield (see Table XX, p. 148). One promising use of leaf litter is as a source of protein which could be extracted from the leaves and incorporated into palatable foodstuffs. Such protein is “not as good as milk protein, but is as good as, or even better than, fish meal” (Pirie, 1962). Pirie (1953, 1958, 1961) has provided cogent arguments for attempting the extraction of protein from forest and agricultural waste on a commercial scale, and the cultivation of useful micro-organisms on the residue. The cultivation of edible fungi on beds of forest litter or on the forest floor itself (“fungal farming”) is another use of litter which might add to the world food supply.
103 The harvesting of present edible fungal growth is still inefficient and haphazard. Smith (1958) notes that conifer forests and plantations of Michigan, U.S.A., each year “burst with great quantities of relatively few species of Boletus”. He suggests that lumber companies could harvest the fungus crop as a means of paying taxes and other costs while the trees are growing to commercial size. Glesinger (1949), in a popular account entitled “The Coming Age of Wood”, points out that the cellulose in wood wastes is capable of being used not only as natural fibre, but as reconstituted cellulose in rayon and plastics, and as raw material for hydrolysis to sugar. The sugar can then be used to produce alcohol, high-protein yeast fodder, and a variety of other useful products. Presumably the cellulose in litter materials could also be so employed, though not as economically. It seems likely that the lignin in wood waste and litter, like the cellulose, can eventually become the raw material for a wide range of chemical conversions, whose industrial importance will increase greatly as reserves of coal and oil dwindle and demands for industrial raw materials grow. Brauns and Brauns (1960, pp. 742-9), in their book on lignin chemistry, point out that this substance is already used (though not on a large scale, in proportion to its availability) in the production of vanillin, plastics, ion-exchange resins, soil stabilizers, fertilizers, rubber reinforcing agents, tanning agents, stabilizers for asphalt emulsions, dispersants in oil-well drilling and other processes, and in ceramic processing. New and large-scale industrial uses will undoubtedly appear as the chemistry of lignin is further investigated. Other litter components beside cellulose and lignin may have industrial potential, the oils and resins in Gymnosperm litter being perhaps the most probable example. If litter is to be utilized commercially, harvest methods will need to be developed. Mechanized raking might serve in well-spaced plantations with closed canopy and little ground flora. I n other types of forest some form of vacuum collection might be devised, since the litter material is loose and unattached. Should litter utilization become economic, it will inevitably involve replacement of the nutrient elements present in the organic debris harvested. Nitrogen is probably the most important of these, but phosphorus, potassium and calcium will also be significant (Tamm, 1958). I n time, nitrogenous fertilizers may be synthesized from atmospheric nitrogen a t low cost, through the use of small nuclear reactors which could provide local sources of power in forested areas. The increasing use of human excretory wastes as fertilizers through sewage processing may also enable a low cost return of nitrogen, phosphorus, potassium and other nutrients to forested areas, especially since the costly sterilization needed for the agricultural use of LITTER PRODUCTION I N FORESTS O F THE WORLD
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J . ROGER BRAY A N D EVILLE GORHAM
sewage will not be necessary in forest areas. Aerial application of various fertilizers may become a widespread technique for economically renewing or improving the fertility of forest soils, as the demand for forest products rises. Even if forest litter does not become an economic raw material in the near future, the study of quantitative aspects of litter-fall remains an important part of forest ecology, dealing with a major pathway for both energy and nutrient transfer in this type of ecosystem. And since litter production is easy to measure in comparison with the difficult and expensive techniques for estimating total net production of forest stands, the possibility that litter-fall might serve as a simple and convenient index to net production provided an additional stimulus for this review. The chief aim of the study, however, is to collate available data on the quantity of litter produced by forests in different parts of the world, -and to assess the influence of environment upon litter-fall under different forest communities.
11. SOURCES OF DATA A. UNPUBLISXED STUDY B Y J . R. BRAY Litter production was measured by Bray from 1957 to 1961 in an Angiosperm forest with a slight admixture of Pinus strobus. This forest occurs on the upper slope of the east bank of the Don River valley at Glendon Hall, Toronto, Canada (43" 40' N, 79' 22' W). It is dominated by Acer saccharurn with a density of 247 treestha. The composition is shown in detail in Table I. I n 1957 and 1958, leaves and stem fragments were collected from the forest floor in late autumn at the close of the period of leaf-fall. These collections were made from 1 f t 2 quadrats (30.5x 30-5 cm) placed at equal intervals along a transect. Newly fallen leaves and any stem material included were lifted intact from the decomposed duff layer in each quadrat. Samples were taken to the laboratory, where each leaf was inspected for signs of decay. If a mesic, calcium-rich leaf (e.g. Acer saccharurn, Fraxinus pennsylvanica) showed only slight decay or tiny holes it was retained as representative of the current crop. If a leaf with a tough, leathery surface (e.g. Quercus boreaZiis, Q. alba) was even moderately decayed, it was rejected as belonging to the previous year's crop. On this basis it was possible to separate the leaves of the current season from those of the previous season in all but a few cases. Samples were then oven-dried at 105°C. I n early winter of 1959, Hty galvanized iron litter pails (0.093m2 in area) were placed in the forest in a regular block pattern. No pail was located beneath a shrub or low sapling which would intercept litter
TABLEI Forest Composition, Glendon Hall, Toronto, Canada Basal area Frequency Density Basal area Importance at breast height index* (treeslha) (m2/tree) (m2/ha) (percentage of total) Density
Acer saccharurn Fraxinus pennsylvanica Pinus strobus Prunus serotina Quercus alba Quercus borealis
247 29 15 44 87 160
-
0.044 0.017 0.128 0.115 0.181 0.116
11.0 0.5 1.9 5.1 15.7 18.6
42.4 6.1 3.0 6.1 18.2 24.2
42.5 5.0 2-5 7.5 15.0 27.5
* Sum of frequency, density and basal area percentages.
20.8 0.9 3.5 9.5 29.9 35.2
106 12 9 23 63
87
106
J . ROGER BRAY A N D EVILLE G O R H A M
from the canopy. Each pail was wired to two adjacent steel posts t o hold it level. The bottom of the pail was slightly above ground surface, and was perforated to allow for drainage of rain and snow melt. A copper screen was placed on the bottom of each pail to prevent tiny litter particles such as bud scales from washing through the drainage holes. Samples were taken at three or more irregular intervals during the year, the major collection being made at the close of leaf-fall. A few leaves blew into the pails in winter and early spring after the canopy opened and leaf-fall was complete. These leaves were discarded from the sample. All stem material in the pails was collected along with that portion of any fallen stem lying directly above the inside perimeter of a pail. All material of animal origin, including fecal matter, was rejected from the sample. Samples from 1960 and 1961 were oven-dried at 70". I n 1958 and 1961 leaf samples were ashed in a muffle furnace at around 550°C for 24 h, to measure mineral content. Litter-fall and ash content are shown in Table 11. The similarity of leaf litter values indicates a rather uniform yearly production. Stem data are much more variable.
TABLEI1 Litter Production in Glendon Hall Forest, Toronto, Canada Litter fall (metric tons/ha/yr) 1957 1958 1960 1961 Mean Leaf, incl. bud scales, fruit Stem, incl. bark Total Ash content of leaves (% d r y w t )
2.8 0.6 3.4
3.2 3.2 6.3
3.2 0.5 3.7
0.8
3-1 3.9
3-1 1.3 4.3
-
7.9
-
9.0
8.4
B. WORLD REVIEW Literature containing data on litter-fall was reviewed in Biological Abstracts, Forestry Abstracts and miscellaneous journals. Coverage is undoubtedly incomplete owing to the wide range of journals and annual reports in which data of this kind are published. Biologists in areas for which data could not be found were consulted for literature references and for unpublished material. We are most grateful to many biologists throughout the world who answered our letters of inquiry. The following have very kindly supplied unpublished data or additional information about published data: Dr D. H. Ashton, Dr J. Brynaert, Dr H. R. De Selm, Mr A. Deville, Mr E. J. Dimock, Mr G. S. Meagher, Mr B. A. Mitchell, Dr J. S. Olson, Dr A. M. Schultz, Dr L. J. Webb, Drs F. D. Hole and G. A. Nielsen.
LITTER PRODUCTION I N FORESTS O F THE WORLD
107
We are especially indebted to the librarians in the reference room of the University of Toronto Library for their expert and unfailing bibliographic assistance.
111. SELECTION AND PRESENTATION O F DATA
A.
CRITERIA FOR ACCEPTANCE
Despite wide variation in methods of litter collection (e.g., raking of cleared surface, cloth or wire screen at soil surface, box or bucket with screen bottom above soil surface) and adequacy of sampling, most of the data examined have been included in this review, in order to obtain maximum coverage. Owing t o the difficulty of equating number, area and type of litter traps, length of exposure, etc., studies of very unequal value have had to be given equal weight. I n the case of Japanese forests (Ohmasa and Mori, 1937) the few data based on less than five plots were omitted. A study by Tarrant et ul. (1951) has been excluded because the data refer mainly to one year's growth of leaves or needles sampled from the lower portion of the crown (G. S. Meagher, private communication). All values based on complete or representative sampling of forest tree canopy have been segregated for separate examination of the yearly standing crop of tree foliage (see Table XIX). No attempt has been made to convert air-dry to oven-dry weights, partly because it has not always been possible to ascertain the method of drying, but also for other reasons. There appears to be considerable variation in weight loss upon further drying. Table I11 shows between 7 and 18% loss in weight by air-dry litter after drying either at an elevated temperature or in vucuo. Ebermayer (1876) reported losses
TABLEI11 Loss of Weight by Air-dried Litter upon Further Drying Material
% weight loss
Fagus sihatica litter Picea abies litter Pinus silvestris litter Fagus silvatica leaves Picea abies needles Picea abies needles Picea abies needles Picea ubiecr needles Populus leaves Bet& litter
18 15 14 9.4 10.0 8.1 6.8 6.9 7.8 10.5
Betub litter
10.8
Angiosperm tree litter Heath and moss litter
8.7 9.5
Drying method
100"c
Authority
Ebermayer, 1876 Ebermayer, 1876 100" c Ebermayer, 1876 Burger, 1925 Burger, 1925 I n vacuo, P,O, Lindberg and Norming, 1943 I n vacuo, P,O, Lindberg and Norming, 1943 100-105" C, 5 h. Lindberg and Norming, 1943 I n vucuo, P,O, AnderssonandEnander,1948 I n vacuo, 20" C Knudsen and Mauritz-Hansson,1939 10@-103°C, 2.6 h. Knudsen and Mauritz-Hansson, 1939 105' C Bray, unpublished In vacuo, P,O, AndrB, 1947
looo c
108
J . ROQER BRAY A N D EVILLE QORHAM
between 14 and 18%, all other losses ranged between 7 and 11%. The average for all data is lo%, whether or not each author's data are combined before averaging. Although air-dry litter may retain appreciable amounts of water, the air-drying process may also result in considerable loss of organic matter. Tamm (1955) reported dry weight losses of 1 to 10% by living pine and spruce needles stored upon moist filter paper during 48 h at room temperature, only about 2% appeared to be lost by respiration. White (1954) observed that needles of Pinus resinosa air-dried for six weeks, and then oven-dried, yielded 9% less dry weight than needles oven-dried immediately at 7OoC. If the needles were left on whole branches during air-drying, the dry weight decline amounted to 14%. It thus appears that in some cases, oven-drying and air-drying of living leaves should give fairly comparable results, since the excess water content of air-dry needles may be balanced by their dry weight losses. Whether the same is true of litter remains to be ascertained. I n any case, differences owing to drying techniques are small compared with variations in litter weight from other causes, and are unlikely to affect seriously any conclusions drawn from the material.
B. ARRANGEMENT The collected records of litter-fall are presented in Table IV, as metric tons of leaves, other, and total litter per hectare per annum (1 metric ton/ha = 892 lb/acre). Owing to rounding off original figures, total litter does not always exactly equal the sum of leaf and other litter. An initial grouping of data is given under four major headings based on broad climatic zones : Equatorial, Warm Temperate, Cool Temperate and Arctic-Alpine. The Equatorial forests are all within a 10" band north and south of the Equator, in Colombia, the Congo, Ghana and Malaya. The Warm Temperate group ranges between about 30" and 40" both south and north of the Equator, including Australia, New Zealand, and southern parts of the U.S.A. (Florida, the Carolinas, Tennessee and California). The Cool Temperate forests in North America range from Missouri and the mountains of California to Minnesota and Quebec, or about latitude 37-47' N; and in Europe from Hungary to Finland, or about 47" to 62" N. Japanese forests are included in this group, for although the mean annual temperature is not greatly different from that of New Zealand, the climate is more extreme, with distinctly cool winters. The scanty Arctic-Alpine data come from stands at 3 000 m altitude in the Sierra Nevada of California, at 800m in southern Norway, and from the Kola Peninsula in the U.S.S.R., the last region being the most northerly at approximately latitude 67" N. Within the broad climatic zones, data are arranged alphabetically by country. For each country the presentation is alphabetically by
TABLEI V Annual Production of Leaf,Other a.nd Total Litter by the Forests of the World Authority
Date
Location
Lat. Long. (approx.)
Jenny el al. Bartholomew et at. Brynaert
1949 Colombia 1953 Congo (Yangambi) p.c. (Ituri)
4s 1N 2N
74w 24E 27E
Laudelot and Meyer
1954
(Yangambi)
1N
24E
Nye
1961 Ghana (Kade)
6N
1w
Mitchell
p.0.
3N
102E
Malaya
Alt. (m)
1700 1800 1650
150
c 600 c 230 c 300 c 450
Ashton
p.c.
Australia (Victoria)
Hatch
1956
(Dwellingup)
Stoate
1958
(Western)
37s
145E
33s
ll6E
c 33s
c ll6E
270
Plant community EQUATORIAL FORESTS Rain forest Forest Ewalyptus saligna Cupressus lwrilanica Mixed forest Musanga ceeropioides, young secondary forest Mawolobium forest Mixed forest Brachystegia forest Dioapyros spp., mature secondary forest Dipterocarpue forest, lowland Dipteromrpus forest lowland Dipterocarpua forest: upland undisturbed Secondary forest, apparently never cultivated, moderately disturbed Secondary forest apparently never cultivated, moherately disturbed Secondary forest apparently never cultivated, mohefately disturbed Dipterocarpue baud%% plantation Druobahnops armnatica plantation Fagraea fragrane plantation Shoreu lepr08uh plantation (close planting) Shorea Zep7osllla plantation (wide planting) FORESTS WARMTEMPERATE (including subtropical) Eucalyptus regnans, mature forest with undergrowth, 47 trees/ha Eucalyptus regnaw, spar forest, 217 trees/ha Eucalyptus regnaw, pole forest, 1013 trees/ha Eucalyptus marginata virgin forest Eucalyptus marginata: pole forest Eucalyptus mnrginata sapling forest Eucalyptue diversieoldr, virgin forest, 0.65 canopy
I=indigenous, E=exotic.
* O=oven
dry, A=air dry.
Origin1 Age
(yr)
I I
E E I I I I I I
Drying methoda
Litter-fall (metric tons/ba/yr Leaves Other T o L 10.2 123
0 22 25
40
8.3 2.9 85
0
7.0
14.9
3.5
15.3 12.4 12.3 10.5 7.2 5.5 6.3
I I I
0
I
0
8.3
I
0
10.5
0
14.4
0
0
I I I
0
I
I
28 28 25 30
0 0 0
9.3 10.9 7.7 14.8
I
30
0
10.2
I
200
4.2
3.9
8.1
I
55
4.1
3.9
8.1
I
25
I I I I
36 c 25
0 0 0
34
3.3
6.9
1.2 2.0 1.6 2.8
1.1 1.1 1.0 2.9
2.4 3.1 2.6
6.7
TABLEIV - continued Authority
Webb
Claudot Miller and Hurst Will
Date
P.C.
Lat.
Location
(North N.S.W.)
Long. (approx.)
Alt.
Warm Temperate Forests-continued Eucalyptus diversieolw, regrowth, 0.87 canopy. Subtropical rain forest, Brgyrodendron Fieus Low suhtropkal rain forest emergent Eucalyptus acmenioides e‘tc. Warm temperate rain forest, Ceratopetalum, Schizotperia Warm temperate rain forest, Ceratopetalum, Schizomeriq Tall warm temperate rain forest with l’riatania eonferta Wet sclerophyll forest, Eucalyptus
c 305 c 15OE
1956 Morocco (Rharb) 1957 New Zealand (Wellington) 1959 (Rotorua)
34N 415 385
zrilularis
7W 175W 176W
Biawell and Schults Blow
p.c. U.S.A. (California) 1955 (Tennessee)
39N 36N
123W 84W
915
De Selm et al.
p.c.
(Tennessee)
36N
848
245
Heyward and Barnette
1936
(N.Florida)
30N
83W
Kittredge Mete
1940 1952
(California) (5. Carolina)
38N 35N
122w 82W
Plant community
(4
Eucalyptus camaldulensia Nothofag? twncata Pinus radzata Pinus radiata P i n w nigra Pseudotsuga ~ z i e s i i Pseudotsuga menziesii L a k t decidua Pintu ponderosa, pure stand Mixed Quercue spp cut over a t 62 yr. Larger trees Q .ldccinea and 9.velutina, Panus virgintuna secondary forest Secondary growth Quercue alba, Q . velulina Q . prinus Pinue palustha second growth, 889 trees/ha Pinus palustns second growth, 1161 trees/ha Pinus palustns second growth, 1947 treeslha Pinus palustns second growth, 2 402 treeslha Pinus caribaea second growth, 1277 trees/ha. Pinus cananenas P i n w taeda, P . eehinata Pinue echinata Pinus taeda Pinus eehinata and mixedangiosnerm8 ~~
l
I=indigenous, E =exotic.
a
0 -oven dry, A=air dry.
Origin‘
Age Drying (yr) method*
Litter-fall (metric tons/halyr) Leaves Other Total
2.7
I
0
3.3
I
0
7.3
I
0
4.5
I
0
5.9
I
0
6.8
I
0
6.0
0 A
4.2 3.5 4.2 5.1 1.5 2.2 2.2 2.1
1.5 3.9 2.0 2.8 1.4 0.7 1.5
0 0
3.8 3.5
0.7 1.0
I
0
2.7
I
0
3.4
I
0
2.7
I
0
3.3
I
0
3.9
I I
0 0 0 0 0
5.0 3.3 4.2 3.8
1 I E
E E P E E I I
I I
I
I I
40 28 45
40 33
45
78 15
20-25 30-40 10 1-60
A A
A A A 0 0
6.0
7.2
6.0 5.7
7.4 6.3 7.9 2.9 2.9 3.7 24
1.3 1.3 0.3 1.6
44 4.6
6.7
6.3
46 4.6
64
TABLEIV - continued Authority
Olson
Date
p.c.
Sims
1932
Biihmerle
1906 Austria
Bray Coldwell and De Long
Location
(Tennessee)
(N.Carolina)
Table11 Canada (Toronto) 1950
(Montreal)
Perina and Vintrova 1958 Czechoslovakia Bornehusch 1937 Denmark (Nsdebo)
Lat. Long. (approx.)
36N
Alt. (m)
Warm Temperate Forest-onlinued Mixed angiosperms and Pinue eehinac Mixed angiosperms and Pinusspp. Mixedsnmosoermq Mixed a n ~ o s ~ e - 6 Mixed angiospem Pinus eehinatu north-facing slope Pinu8cehinatu:south-facina slope Pinua eehina&level upland Liriodendrontulipifera Pqpulua, Frminzlsin sinkhold Querctls Carua Liriodendron lulip$era,ndrth-facing slope Q w m s ,Carya, Liriodendron lulipifera,south-f3cin~slope Quercua Carya, Liriaddrmi .!uZip$era, level upland uercu.9,Carya, Liriodendron valley inwr - uercud forest,unburned Pinus - 8uercus forest,burned
84W
36N
83W
48N
16E
44N
80W
47N
74W
B
COOLT E ~ E R A T E FORESTS Pinua niura plantation Pinus nigra plantation 120 Acer saccharurn Quermsboralis alba slight’admixtnre Pi& %obua’ Beer saccharuna
c 49N c l 8 E 56N 12E
Boysen-Jensen
1930
(Sor0)
56N
12E
Moller Aaltonen (data of Svinhnfvud)
1945 1948 Finland (South)
56N c 62N
12E c22E
Plant community
*I=indigenous, E=exotic.
Origin1 Age Drying (yr) method’
Litter-fall Leaves Other Total (metric tons/ha/n)
I
1-60
0
4.3
1.7
6.0
I I I I I I I I
1-40 1-150 1-50 1-45
0
3.6 46 4.1 4.1
1.1 07
4.6 53 4.7 61
0
0 0 0 0 0 0
09
6.6
6.2 3.8 4.7
I
4.0
I
5.0
I
6.4
I
6.3 3.5 2.0
I I
I I I
37 57 60-200
0 0 0
3.1
I
0
3.4
I I I
0
0 0
A
2.2 1.7 1.7 2.2 1.6
Fagus grandifolia Betula populifolia Pwulus arandidenlata. P. trmuloidee Pi+&spl Piceaabie6,stem diam.6 cm., 7 000/ha Picea abies, stem diam. 10 cm., 3 700/ha P i c a abiee, stem diam.21 cm., 1200/ha Fraxanue excelsior.unthinned Fraxinus excelsior,thinned Fagus silvatica PinUS 8dVestl.is
I
A
1.2
I
A
1.6
Picea abiea
I
O=oven dry, A=air dry.
0.6
I
I I I I
94
1.3
3.5 3.8 4.3
1.4
34
12 12 5-200 A
1.0
TABLEI V - continued Authoilty
viro
Danckelmann
Danckelmann
Date
1056
Location
Lat. Long. (approx.)
Alt.
(Eva)
61N
25E
105
(Vilppula) (Eva)
62N 61N
25E 25E
105 105
(Hyytiala) (Vesijako)
62N 61N
24E 25E
150 110
48N
11E
1887a Germany (5.Bavaria)
18871,
(throughout)
c 50N
(m)
c 10E
'I=indigenous, E=exotic.
Plant community Cool Temperate Forests-continued Belula Pinussilvestris Pinuasilve.at+ Pinussilvestrzd Piceaabies Picea abies Pieeaabia Betula Betula Pinus silvestris,plantations on good soils Pinwr silvestri.8, plantations on good soils Pinus silvertris, plantatibns on good soils Pinus silvestris,plantations on good SOilS Pinus silvestri.8, plantations on good soils Pinus silvestris,plantations on moderately good to poor soils Pinus silvestris, plantationson moderately good to poor soils Pinus silvest7i.8,plantationson moderately good to poor SOUS Pinus stluestrzd,plantations on moderately good to poorsoils Pinus siZvestri8,plantations on moderately good to poor solls
Fagus silvatiea, good to moderately good Soil8 Fugwr silvatiea, good to moderately good soils Fagua silvutieu, good to moderately good soils Fagus silvdica, good to moderately good soils Fagus silvdim, good to moderately good soils Fagus silvatica, fair to poor soils Fagwr silvatica fair to poor oils Fugw silvuth: fair to poor soils Picea at+ Pieea a h 8 O=oven dry, A=air dry.
Origin1
I I
I I I I I I
Age Drying (yr) methoda
50 88 58 68
A 0
78
0 0 0 0 0
I I
86 21-40
0 A
91
0
Litter-fall (metric tons/ha/yr) Leaves Other Total
1.7 1.2
0.6 0.6
1.9 1.9 1.7 1.3
1.0 0.5 0.4 0.5
1.9 2.3 1.8 2.7 2.8 2.4 2.2 1.8 1.5 3.3
I
4140
A
3.2
I
61-80
A
3.2
I
81-100
A
3.1
I
100
A
3.0
I
21-40
A
2.4
I
41-60
A
2.3
I
61-80
A
2.2
I
81-100
A
2.0
I
100
A
1.9
I
21-40
A
3.6
I
41-60
A
4.2
I
61-80
A
4.6
I
81-100
A
5.0
I
100
A
4.6
I
4140 61-80 81-100 21-40 41-60
A A A A A
3.9 4.2 3.1 3.7
I I
I I
3.6
TABLEI V - continued Authority
Ebermayer
Ebermayer (data of Hartin)
Date
1876
1876
Location
(Bavaria)
Lat. Long. (approx.)
c 49N
c 12E
Alt. (m)
Plant community
Cool Temperate Forest&-continued Picea abies Pieea dies Picea abies Fagus silvatica Fagua &vat+ Fagus silvatwa P i c a abies P i c a abiea Picea abies Picea abies Pinus si1veatri.a Pinus 6ilvestri.a Pinua eilvestris Faqua silvatica
Origin'
Age Drying (yr) methoda 61-80 81-100 100 30-60 60-90 90 30 30-60 60-90 90 25-50 50-75 75-100 80 100
A A A 0 0 0 0 0
0
0 0
0 0
A A
Litter-fall (metric tons/hs/gr) Leaves Other Total 3.8 3.6 3.4 3.4 3.4 3.3
4.5
3.4 2.9 2.8 2.9 3.0 3.6 4.0 3.8
TABLEIV - continued Authority
Ohmasa and Kori
Date
1937 Japan
Location
(Kunadacs) (Godollo) . (Era) (Kunadacs) (Retsag) (Godollo) (Ugod) (Rallol (Kunadacs) (Kallo) (Matra) (Kallo) (Kallo) (Godollo) (Retsag)' (Godollo)
Witkamp and van der Drift
1961 Netherlands (Amhem)
Bonnevie-Svendsen and Qjem
1967 Norway (Eidsberg)
Lat. Long. (wwox.)
Ale. (m)
Plant community Cool Temperate Forests-continued Populus (Hungarian szurke) Populue nigra hybrid UZmw (Hungarian venic) Betula
48N
48N
22E 201
c 36N c 136W
62N
I
W W U 8 8Ee8aflo7U
I I
uercue robur
Chanzaecyparisobtuea Pinue denaiflora Pinus thunbergii Thujopsid dolabrata Lark kampferc (leptolepia) Abies eaclutlinensur PieeajEZO6nSd Pieea glehnii Caetanea crenata Betula latifolia Quercuarobur, Betula vem(coda, mor
6E
.nil
60N
11E
160
61N 62N 6ON 6ON
11E 11E 12E 11E
69N
10E
170 330 250 80 250 150 170 50
I =indigenous, E =exotic.
mull Boil b r k Sibirieo on brown earth
Lark silririca on brown earth La& sibirica on iron podzol Lark decidua on iron podzol La& l@ptol,e& on brown earth
Pieea abies on iron podzol Pieea a h 8 on brown earth Picea abies on brown earth Pice0 abkd on brown earth (tram. to nnaroii r"-"".,
0 =oven dry, A =air dry.
Age Drying (yr) method' 24 35 40 30 35 45 70
w c u e robur
~ e i & cerruco~)a,&tletnur rob~r,etc., (Ringsaker) (Storelvdal) (Qrue)
Origin'
I E E E I
83
51
60
70 75 76 12-16 28 45
A A A A A A A A A A A A A A A
A
3.8 1.8 2.5 3.6 3.9 2.0 1.1 1.6 1.6 1.9 1.4 2.3 2.8 1.6 2.7
1.0
3.7
A
2.6
1.6
41
I I I
I I
I E E E I E I I I I
4.4 4.0 4.9 3.6 3.3 3.8 2.7 3.4 4.0 44 4.7 4.6 38 41 4.5 6.0
A
I I
I I I I I I .I
Litter-fall (metric tons/ha/yr) Leaves Other Tow
45
0
2.8
36 60 90 30 80 60 30-40 45-66
0 0 0 0 0 0 0 0
2.8 1.2 2.1 3.4 2.0 3.z 2.0 46
TABLEI V - continued Authority
Date
Location
Lat. Long. (approx.)
Origin'
Age
Drying
I I
90-130 80
0 0
I I I I I
26 39 63 62
0 0 0 0 0
2.5 1.6 1.3
0.6
0.3 0.0
3.1 3.1 1.0 1.0
0.1
1.7
(yr) method'
Litter-fall (metric tOns/ha/yr Leaves Other T o L
1939
(Stockholm)
69N
18E
I
0
1.6
1943
(Stockholm)
SON
18E
Pieea abiea
I
0
3.1
1038 1964
(S.W. Dalama)
(Lurid)
66N 60N
13E 16E
I I
A
2.8 1.7
47N
9E
Mixed angiosperms Betula pubeseens, open parkland (46% canopy) Fagus dlvdiea
York
Ehwald (dataof Liebundgut)
1967 Switzerland (Zurich)
Kendrlck Owen Wright
1069 U.K.(Cheshire) 1964 (N. Wales) 1967 (Roxburghahire)
330 60
61N
11E
69N
18E
63N 63N 66N
1033 U.S.A.(Minnesota) 1030 (hfinnesota)
47N 47N
96W 92W
Anonymous Chandler
1960 1941
(Missouri) (New York)
c 39N
c 92W
1944
(NewYork)
43N
42N
80 80 180 180
3w 4w 3w
Alway et al. Alway and Zon
Chandler
Plant community Cool Temperate Forests-continued Pinus silvestrb on iron podzol Fagus silvatiea on brown earth (trans. to podzol) F a g w siludiea on brown earth Pieea abiee Pieea ab-ia Bet& Populust remula, herb-rich, some Betula and Cmylus Betula pubeacend and hybrids
(Storelvdal) (Brunlanes)
Anderason and Enauder b u d s e n and Yauritz-Hanaaon Lindberg and Norming .Lindquist Sjors
Alt. (m)
77w
._..
7RW
I -indigenous, E =exotic.
Fagus eilvdica Pinus silvegtris Picea suchensis Picea abiet?, light low thinning, 460 trees/ha Pieea abies, medium thinning, 237 treestha Picea abies, heavy thinning, 67 trees/ha Pieea abiea, light crown thinning, 152 trees/ha deer saecharum and Tilia ame&ann Pinus banksiana and P . resinosa Pinus resmnosa Pinus bankaiana Pinus resinosa and P. 8trobun Pinus banksiana Pinus echinata Acer saccharurn and some mixed angiosperms Tilia americana and some mixed angiosperms aneiosDerms Tilia-americana, Tilia americana, Q y e w rubra, Carya cordifomzts Acer saccharurn, QUErcuS rubra, R little Fagus grandifolio Pinus strobus
* 0 =oven
dry, A =air dry.
I
P
A
60
2.0 2.6
19
2.8
0 0 0
4.1 2.1
0.7
1-7 48
E E
30 ,46
0 0
E
46
0
4.3
E
46
0
3.7
E
46
0
I I I I I I I I
60
0 0 0 0 0 0
2.2 2.0 2.2 2.1 2.0 2.0
30-70
0
3.3
I
30-70
0
3.1
I
30-70
0
2.9
I
30-70
0
2.9
I
c24
0
3.1
5.7
4.2
38
TABLEI V - continued Authority
Dimock
Hole and Nieleen Jenny el al.
Date
1958
p.c. 1949
Location
(Washington State)
(Wisconsin) (California)
Lat. Long. (approx.) 44N 42N 42N 44N 44N 44N 44N 47N
43N 37N
74w 76W 76W 74w 74w 74w
74w
123W
89W ll9W
Lnnt
1951
(Connecticut)
42N
73w
Scott
1955
(Connecticut)
42N
73w
Ehwald (data of Abramova)
1957 U.S.S.R.(Velikije Luki)
57N
31E
Ehwald (data of Bykova)
1957
62N
391
Ehwald (data of Nesterov)
Ehwald (data of Sacharov)
1967
1957
(Voronezh)
(MOSCOW)
(Brjansk)
66N
63N
Alt. (m)
Plant community
Cool Temperate Forests--eontinued Pinus atrobus Pinua reainosa Picea abies Picea rubens Tauga canadensis Thuja oceidenlalis Abiea balsamea 330 Paeudotauga menziesii unthiuned 300 Paeudotauga menzicsi( light thinning 320 Pseudotsuga menzhii, medium thinning 310 Paeudotsuga menziesii, heavy thinning 290 w c u a alba Q.vdutina, 420 treespa 1200wrcua kedggii 1800 1 200- Pinusponderoaa 2 200 1500 Wxed gymnosperms Pinua resinoaa Pinus strobus Beer aaccharum, Qww rubra and mixed angiosperms Pinus strobua P i c a abiea with Ozalis &a& ground flora PGea abiea with Vmcini:ummurtillw, grouud Eora Pinus advestria
8
Age
Drying method*
I I E I I I I I I I
65 c24 c24 150 150 65 25 45 46 45
0 0 0 0 0 0 0
I
45
0
(yr)
0 0
Litter-fall (metric tonslhaly~) Leaves Other Total 2.9 3.8 3.9
1.9 1.5
0
1.1
I I
100-125 60-100
0
I
is0
o
2.1
0
46
I I I I
50 30-50
I I I I I I I I
0
4.6
1.5
0
4.0 4.0 2.1
0 A
1.7 4.6
A 20
40
60
80
100
6.2 1.3
0 0 0
0 0
37 2.5 2.3 1.9 2.0 1.3
Pinua silvurtria with Qww
I
A
3.0
Pinus silvurtria with Beer Pinus silveatris with mixed spp. Pieeaabies withSambunwr understory Pica a b h Pinua ailveetris with Vaccinium &is-idaea ground flora Pinus ailvurtris with Colylus under-
I I I
A A A
3.6 4.2 8.2
38E
34E
Origin1
at,nro
I=iudigenous, E=exotic.
* 0 =oven
dry, A=air dry.
45-68
I I
A? A
2.7
0.6
6.9 3.2
I
A
4.7
2.2
6.0
TABLEI V - continued Authority
Date
Location
(Velikije Luki)
Lat. Long. (approx.)
I I
Populus tremula, with Cowlus and some ground flora Populus tremula with Cmylu8, Tilia and much modnd flora P o p u l u hemka-w ~ ith TiEia Acer platunoides add much grdund flora Pinus siluestris with Quercwr Pinus siluestris with Acer Pinus siluestris with Vaecinium sitis-idma eronnd . .. . -- -~~flora Quercusplantation Quercus and Frazinus plantation Quercus, Fraxinus and Caragann lnicrophylla Quercusand deer Quercuswith Begopodiumground flora Quernur with Aegopodium and Carex ground flora Qu.ercu.8,solonetz soil Populus, density 0.75,1688trees/ha (thinned) Pomlus densitv 1.0. 2 460 treeslha (thinned) Populus density 0.8, 988 trees/ha (thinnkd) Populus, density 1.1,1464trees/ha
I
10
0
3.9
I
25
0
4.1
I I I I
50
0
4.9
(Kiev)
51N
31E
1953
(Voronezh)
52"
39E
(Derkul steppe)
52N 49N
393
~~
40E
(unspecified) Sviridova
1960
(Voronezh)
52N
39E
"
Mork
Jenny et al. Levina
1942 Norway (Hirkjolen)
1949 U.S.A. (California) 1960 U.S.S.R. (Kola Peninsula)
62N
37N
67N
10E
119w 37E
800
3 000
0 hi
La
Litter-fall (metric tons/ha/yr) Leave8 Other Total
P i c a abks with mixed angiosperms Pinus siluestris
1957
(Voronezh)
Drying methoda
I I
Ehwald (data of Zrazevskij and Krot) Remezov and Bykova
1960
Origin1 Age (yr)
31E
1957
Sonn
Plant community Cool Teniyeralc Forcsls-- continued Picea abies with Vacciniuni mrrtiUu8 and Ozalis aceloselln groiind flora Picea ubies with Relula sp.
Ehwald (data of Smirnova)
57N
Alt. (m)
I =indigenous, E =exotic.
* 0=oven
dry, A =air dry.
A
3.3
1.6
4.9
0
1.5
0.5
2.0
0 10,45,105 0
2.1
0.6
2.7 2.4
1.3 2.0 4.5
30 60
15
3.3 3.1 4.3
50 c 210 130
5.2 4.1 4.1
25
I
ALPINEAND ARCTICFORESTS Picea abies, very slight Betula admixture Pinue siluestri-9,appreciable Belula admixture Betula Pinus conlorta Pinue siluestris with Cladonia ground flora Pinwr silveetri.8 with H~loconzium ground flora
70 38-90
I I I I I I
c 170 30
A
30
A
55
A
5.4
55
A
4.6
1.4 6.0
5.2
el35
0
0.9
0.6
c200
0
0.5
0.3
0.8
c 105 200
0 0
0.6
0.2
0.8
1.5
1.2 0.6 1.0
118
J . ROGER BRAY AND EVILLE GORHAM
author, which involves some separation of data from the same areas within the U.S.A. and the U.S.S.R.
IV. LITTERCOMPONENTS A. DETAILED LITTER SEPARATION Table V shows that leaf material contributed 60-76y0 of litter for the species listed, branches 12-15%, bark <1-14y0 and fruit <1-17%. Trees with loose dehiscent bark produced considerably more bark litter TABLEV Detailed separation of Litter Cmponents Percentage of total litter Leaf Fruit Branch Bark Other*
Pinua Pinua Pinua Picea Picea-Betulu Betula Quercua Eucalyptua
60 62 69 73 76 71 75 60
11 17 2 5 6
-
t l 15t
12 1-21-+] 12 13
14 11
-
k-,l8-----+I
12 <1 15 9 )-2b+]
<1 6 10 16 -
Authority Perina and Vintrova, 1958
Mork, 1942
Viro, 1955 Viro, 1955 Mork, 1942 Viro, 1955 Nieleen and Hole, p.c. Hatch. 1955
* Flowers, bud scales, fragments, epiphytes, insects.
t Including buds.
than did tight-barked trees. For example, the floor of a Eucalyptus forest was often covered with fallen bark; and Pinw forests, particularly of P. resinosa, also showed a high bark-fall. Bark litter from Pagw, Carpinw and other tight-barked trees was negligible. The variation of fruit litter reflects the widely varying fruit size and production of tree species and the usually short period over which litter is sampled. Curtis (1959) found that an Acer saccharurn forest produced from 99 000 seeds/ha/yr to 13 million seeds/ha/yr. Miller and Hurst (1957) noted great annual variation in seed production by a pure Nothofagus truncata forest, and observed that hot dry summers favored flowering. The occurrence of “mast years” in true beech (B’agw)forests is well known. B. PERCENTAGE O F NON-LEAF LITTER The difficulties of sampling tree stem litter have been noted frequently. Nye (1961) observed that timber-fall over a small area was very erratic and difficult to measure, since it was influenced greatly by the fall of even a single large tree. Data from Toronto (Table 11)
LITTER PRODUCTION IN FORESTS OF THE WORLD
119
showed stem litter ranging from 14 to 50% of total yearly litter over four years. Non-leaf litter data in Table IV range from 2.8% in an angiosperm stand of Bonnevie and Gjems (1957) to 55% in an Angiosperm forest of Stoate (1958). These variations emphasize that stem litter sampling requires larger areas and longer time spans than leaf litter sampling if accurate comparisons of the two are to be made. * On average, non-leaf litter makes up about 27 to 31% of the total, as shown by Table VI. The mean of all values is 30%. Values for AngioTABLEVI Percentage of Non-leaf Material in Forest Litter
All species
Angiosperms Gymnosperms
BY
Individual values
author
30 30 29
30 31 27
sperms are slightly higher than those for Gymnosperms, owing mainly to high values for several Australian Warm Temperate species. If the data are divided into latitudinal zones (Table VII), Warm Temperate TABLEVII Percentage of Non-leaf Litter in Different Climates* Climate Gymnosperms Tropical Warm Temperate, Australia and New Zealand (39) Warm Temperate. North America 37 Cool Temperate 23 Arctic-Alpine (39)
Angiosperms (33) 42 23 21 21
~~
*Figures in brackets represent a single author’s data.
areas tend to have a higher non-leaf litter percentage than Cool Temperate areas. This relationship is especially evident in the Gymnosperm species. Among Angiosperms this tendency is less clear, for while the Warm Temperate forests of Australia include many loose-barked trees (e.g. Eucalyptus), the forests of the southern U.S.A. show lower nonleaf litter percentages similar to those of their Cool Temperate counterparts farther north.
c.
UNDERSTORY LITTER
The contribution of understory plants to forest litter is closely related to the density of the forest canopy and light penetration to the under-
TABLEV I I I Understory Litter Species
Understory litter (metric (yoof total tonslhalyr) litter)
Eucalyptus regnans mature forest, 47 treeslha Eucalyptus regnans spar forest, 217 treeslha Eucalyptus regnans pole forest, 1013 trees/ha Robinia pseudacacia, 9 yr Sassafras albidum, 12 yr Larix leptolepis Larix sibirica Picea abies Pinus silvestris Ulmus glabra and mixed Angiosperms Pinus strobus Acer sacchrum Populus tremula, 30 yr, 2 460 treeslha Populus tremula, 30 yr, 1688 treeslha Populus tremula, 55 yr, 1464 treeslha Populus trernula, 55 yr. 988 trees/ha Quercus robur Mixed Angiosperms, cut in 1940
* Probably includea lower story trees. t Living material harvested in mid-summer.
2*0* 0.9*
0.8*
1.1.t 0.210.3 0.2 0.1
0.2
0.3 0.3 0.3 0.4 0.5f 0.3
0.35 0-1 0.8
25 11 11 28 7 10 7
3 7 10 16 15 8 10 8 6 4 20
Authority
Ashton (P.c.) Ashton (P.c.) Ashton (P.c.) Auten, 1941 Auten, 1941 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Bonnevie-Svendsen and Gjems, 1957 Lindquist, 1938 Scott, 1955 Scott, 1955 Sviridova, 1960 Sviridova, 1960 Sviridova, 1960 Sviridova, 1960 Witkamp and van der Drift, 1961 Witkamp and van der Drift, 1961
f Improvement cut 1952, sampled 195S58. 8 Improvement cut 1940-42, sampled 1955-58.
LITTER PRODUCTION I N FORESTS OF THE WORLD
121
story. Data in Table VIII reveal that the maximum contribution of understory plants to total litter is 28% in a very young stand of Robinia, while an old open stand of Eucalyptus reaches 25%. Another high value of 20% is exhibited by a mixed Angiosperm stand (height 6.5-10.5 m) opened by cutting. Other values range from 3 to IS%, and average 9%.
D.
MINERAL MATERIAL
Forest litter is not wholly organic, but always contains some mineral matter. Table I X provides average values for the ash content of litter from Angiosperm and Gymnosperm species in North America and Fennoscandia. I n both regions, the Angiosperm group, and especially the non-fagaceous Angiosperms, contained more mineral material than the Gymnosperm group ; with the majority of Gymnosperms having from 2 to 6% ash, the majority of Fagaceae from 4 to 8% ash and the majority of non-fagaceous Angiosperms from 8 to 14% ash content. Mean ash content as a percentage of dry matter of the nineteen Gymnosperm species was 3-7%, of the thirteen species of Fagaceae 6.3%, and of the forty-three non-fagaceous Angiosperms 10.4%. Among genera summarized in Table I X with two or more species, mean per cent ash contents are as follows : Gymnosperms, Pinus, 3.0; Picea, 4.5 ; Juniperus, 4.6 ;Larix, 5.2 ;Fagaceae, Castanea, 4.4; Quercus, 6.6; F q u s , 6-9; non-fagaceous Angiosperms, Acacia, 4.8 ; Populus, 5.5 ; Betula, 5.8; Prunus, 7-7; Acer, 8.4; Diospyros, 9.0; Fraxinus, 10.7; Aesculus, 14.7; Ulmus, 16.1; Morus, 16.3; Celtis, 21-4. Broadfoot and Pierre (1939) present ash contents of leaf litter from trees in West Virginia, U.S.A., indicating a range of from 2 to 3% dry weight for three Pinus species (P. strobus, P . rigida, and P. virginiana). Juniperus virginiana had 5% ash. Leaf litter from fifteen Angiosperm tree species ranged from 3 to 12% ash. It is noteworthy that ash content is usually low for taxa in Table IX such as Acacia, Betulu, Castanea, Juniperus, Pinus, Populw, and Quercus, which are usually pioneer in forest development and which often occur on the more infertile sites. There is a higher ash content in taxa such as Acer saccharurn, Aesculus, .Celtis, Cladrastis lutea, Diospyros,
Praxinus, Juglans nigra, Liriodendron tulipifera, Magnolia macrophytla, Morus, Tilia americana and Ulmus, which usually occur in the more developed (or “climax”) forest communities and on the more mesic and fertile soils. Ash content of litter may vary with region, owing mainly to soil differences. For example, among the Fennoscandian data, those from Finland tend to be rather low. Detailed analyses of the major elements comprising the mineral material in litter are numerous, and have been reviewed extensively
TABLEI X Ash. Content of Litter from Various Trees ~
~
~~~~~~~~
North America
Ash yo of dry weight
1
Scott, 1955 (freshly fallen leaves or foliage)
"
Joffe, 1949 (old leaves)
*Various authors
Frequency
Gymnosperms
Fagaceae Non-fagaceous Angiosperms
Pinus rigida Pinus silvestris
2
4
Fennoscandia*
2
0
0
Pinus rigida
Pinus reainosa Pinus strobus
Pinus silveatris
4
0
0
Pinus banksiana Pinus cari baea Pinw, palustris Quercus borealis
Abies balsamea Picea rubens Populus grandidentata
Larix leptolepia
6
1
1
Acacia angustissima Caatanea sativa Juniperus pinchotii Juniperus utahensia Pinus resinosa
Betula popal~olia Acer rubrum Castanea vulgaris
3
2
3
3
3
4
Acacia roemeriana Acer rubrum Pinus strobus Quercus alba Quercus breviloba Quercus palustris
Betula pabeacens and vermosa Sorbua aucuparia Larix sibirica P i c a abies
* Anderssonand Enander, 1948. Bonnevie-Svendsenand Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson,1939. Mork, 1942. Viro, 1955.
TABLEIX - continued North America Ash yo of dry weight 6-
Scott, 1955 (freshly fallen leaves or foliage)
Fennoscandia*
Joffe, 1949 (old leaves)
Fagua grandqolia Quercus virginiana sndifolia mnsylvanica 8
9
10
11
Diospyros virginiana Fraxinus excelsior Fraxinus quadrangulata Liquidambar styraci$ua Prunus serotim
*Various authors
1
3
0
Populus tremzclcl Quercus robur
0
3
4
0
0
6
0
0
6
0
1
3
0
0
3
Carya ovata Catalpa speciosa CornusJorida Diospyros texana Magnolia macrophylla Platanus occidentalis Fraxinua americana
Ulmus americana
Robinia pseudmacia
Fagaceae Non-fagaceom Angiosperms
L a r k decidwz Fagua silvatica
Acer smcharum
Liriodendron tulipij'era Quercus douglaaii Tilia americam
Frequency
Gymnosperms
Acer platanoides
* Andersson and Enander, 1948. Bonnevie-Svendsen and Gjems, 1957. Hesselman, 1925. Knudsen and Mauritz-Hansson,1939. Mork, 1942. Viro, 1955.
TABLEIX - continued North America Ash % of dry weight
-13
Scott, 1955 (freshly fallen leaves or foliage)
-.
Joffe, 1949 (old leaves)
*Various authors
Freauencv
Gymnosperms
Fagaceae Non-fagacsoua Angiosperms
Acer saccharurn
0
0
1
Cladrastis lutea Juglans nigra
0
0
2
Aesculus glabra Robinia pseudacack
0
0
2
0
0
3
0
0
2
0
0
2
Aesculus calijornica Celtis reticulata 16
Fennoscandia*
Fraxinus excelsior
Morus microphylla Morus rubra Celtis occidentalis 26.0
Ulmus scabra 21.3
* AnderssonandEnander, 1948.Bonnevie-SvendsenctndGjems, 1957.Hewelman, 1925.KnudeenandMaurita-Hamson,1939.
Mork, 1942. Viro, 1955.
LITTER PRODUCTION I N FORESTS O F THE WORLD
125
by Lutz and Chandler (1946). Many more recent references may be found in the bibliography at the end of this review. Analyses for several of the minor elements have been made by Scott (1955).
E.
ORGANIC MATERIAL
The organic fractions of forest litter are not a t all well known. Crude proximate analyses of fresh leaf litter from four Gymnosperm and four Angiosperm tree species in eastern North America were carried out according to the methods of Waksman (see Handley, 1954) by Melin (1930), and a similar series of analyses is available for four Angiosperm and four Gymnosperm species in Finland (Mikola, 1954). These may be of interest to persons concerned with the possible utilization of leaf litter. Ether soluble components ranged from 4 to 12% dry weight, coldwater soluble organic matter from 3 to 14%, hot-water soluble organic matter from 3 to 9yo,and alcohol soluble organic material from 3 to 13%. “Hemicelluloses”, estimated crudely from sugars produced by dilute acid hydrolysis of alkali extracts, ranged from 10 to 19% dry weight. “Celluloses”, also crudely estimated by treatment of hemicellulose residues with Schweitzer’s reagent, ranged from 10 to 22%. “Ligninhumus”, the residue remaining after extraction of litter with a mixture containing 10 ml of 18% HC1 and 50 ml of 72% H,SO,, ranged from 5 to 33%. “Crude protein”, estimated by subtracting water-soluble from total nitrogen and multiplying the result by 6.25, ranged from 2 to 15% dry weight. Differences between Gymnosperms and Angiosperms were not consistent. Handley (1954), in discussing such analyses, cites some by Wittich (using methods somewhat different from those above) of German Angiosperm tree litter. These give the following ranges, as percentage of ash-free d q matter: ether soluble 6-14, coldwater soluble 6-25, hot-water soluble P 1 0 , alcohol soluble 2-5, hemicelluloses 25-36, celluloses 7-25, lignin-humus 11-30 and lignin (by acetyl bromide separation) <1-8. Nykvist (1963) has recently investigated the water-soluble aminoacids, sugars and aliphatic acids in Angiosperm and Gymnosperm litter from Swedish forest tree species.
V. FACTORS AFFECTINGLITTER-FALL A.
EVERGREEN GYMNOSPERMS AND DECIDUOUS ANGIOSPERMS
Because of their evergreen nature, Gymnosperms might be expected to be more productive than deciduous Angiosperm trees, although this factor may be countered to some extent by the tendency for Angiosperm forests to occupy more fertile sites. As far as litter-fall is concerned, Table X indicates that when a wide range of sites is considered I2
C.E.R.
126
J . ROGER BRAY A N D EVILLE QORHAM
TABLEX A Comparison of Litter Production by Evergreen and Deciduous Trees in the Northern Hemisphere
Evergreen Deciduous Gymnosperms Angiosperms (metrictons/he/yr) 3.7 3.2 2.6 2.4
No. regions averaged
Total litter Leaf litter
by difference
Other litter observed
8 9
4
1.1 0.7
0.8
0.7
Gymnosperms yield about one-sixth more total litter annually than Angiosperms, the difference amounting to 0-5 t/ha. The difference for leaf litter alone is 8% (0.2 t/ha), and for those stands where other litter was actually collected the Gymnosperm yield was about the same as that of Angiosperm trees, 0.7 t/ha. (In computing averages from combined data, only those countries or states were considered for which both evergreen Gymnosperm and deciduous Angiosperm stand data were available. The averages in Table X, and in Table XI, are based on combined data for each country, with each American or Australian state, TABLEX I Annual Litter Production in Four Major Climatic Zones Leaves Other Total no. regions metric no. regions metric no. regions metric averaged tons/ha averaged tons/ha averaged tons/ha Arctic-Alpine
1
0.7
1
0.4
3
1.0
15
2.5
10
0.9
22
3.5
Warm Temperate
8
3.6
5
1.9
7
5.5
Equatorial
2
6.8
1
3.5
4
10.9
Cool Temperate
and the Werent major areas of the U.S.S.R., treated as countries, except for the following which are grouped - the New England states, the Carolinas.) Data on net production (Table XX) support the generalization that Gymnosperm trees are somewhat more productive than Angiosperm trees, the difference amounting to about one-quarter (2.6 t/ha) for total above- and below-ground production. For leaves the difference is slight (see also data on standing crops of leaves in Table XIX). Specific areas do not always follow the above tendency. For example, within Germany the averages of data in Table I V show somewhat
L I T T E R PRODUCTION I N F O R E S T S OF T H E W O R L D
127
greater total litter production by the deciduous F q u s silvatica, 3.8 t/ha, than by the evergreens Picea abies, 3.5 t/ha, and Pinus silvestris, 3.0 t/ha. If only Ebermayer’s individual data are examined a somewhat different situation is evident, with Fagus averaging 3.3, Pinus 3.2 and Picea 3.0 t/ha (Lutz and Chandler, 1946). B.
ENVIRONMENT
7. Climate and Latitude The predominant influence of climate upon litter production is shown in a general way by Table XI, which summarizes the data for major climatic zones. I n Arctic-Alpine forests total litter production averages 1 t/ha annually, while in Equatorial forests the mean is almost 11 t/ha.i Cool and Warm Temperate forests average 3.5 and 5-5 t/ha respectively. I n round figures the ratios are about 1: 3 : 5 : 10 for the major climatic zones. The range of mean annual temperature spanned by these climatic zones is from below freezing for the most northerly Arctic forests to about 25°C for those of the hottest Equatorial regions. From a biological standpoint the length of the period when temperatures are above freezing is also important. It is of course year-long in the Equatorial forests, and almost so in the Warm Temperate stands; but in Arctic-Alpineregions the mean daily temperature may be above freezing for 6 months or less. The growing season may be considerabIy shorter, for example Paterson (1961) indicates that in parts of northern Fennoscandia the growing season for Gymnosperm forests may be as short as 3 months per annum, while in .Cool Temperate forests it is often about 6 to 7 months in duration. Associated with the higher temperature and longer growing season of the Equatorial zone is the greater amount of insolation during the period of photosynthesis. This must be of considerable importance for primary productivity. Some preliminary calculations based on maps of Black (1956) suggest that the total amount of solar radiation received during the growing season is roughly in the proportion of 1: 3 : 5 for extreme Arctic-Alpine, Cool Temperate and Equatorial sites. I n the Arctic-Alpine sites it is probably less effectively utilized owing to the more open nature of the forest and to the relative coldness of the soil. Data for both leaf and other litter, while less extensive than those for total litter, bear out the general climatic relationship. (In this con-
t I n view of the scarcity of tropical data it may be of interest to note a total annual litter-fall of 14 t/ha by Eucalyptus in Brazil, measured over 8 years (Navarro de Andrade, 1941).This value has not been included in the tables because no further information ia available, particularly as to whether this is dry weight (though it seems unlikely to be otherwise).
128
J . ROGER BRAY AND EVILLE QORHAM
nection it should be borne in mind that the three categories of litter summarized in Table XI do not represent matched sets of data, for some authors collected only leaf litter, and some of those collecting total litter did not separate leaf and other litter.) Leaf litter ranges from 0.7 tjha in Alpine Norwegian forest to nearly 7 t/ha in Equatorial Africa, with the Cool and Warm Temperate zones intermediate a t 2.5 and 3.6 tjha respectively. Data for non-leaf litter are least satisfactory, with less coverage and also less reliability because of the irregular and '4t
NORTH
O R SOUTH LATITUDE ( d e g r e e s 1
FIG.1. Annual production of total litter in relation to latitude. Open triangles equatorial, solid triangles -warm temperate, circles - cool temperate North American (open)and European (closed),squares -Arctic-Alpine. Line fitted visually to means for climatic zones, shown by large crosses. One alpine Californian stand is excluded.
occasional deposition of large branches upon collecting sites. However, even in this instance the annual production in the Norwegian mountains is about one-ninth that in Ghana, 0.4 as against 3.5 tjha. Again the Cool and Warm Temperate forests are intermediate, with 0.9 and 1.9 t/ha. The major role of temperature in controlling litter production is well illustrated in Fig. 1, where total annual litter-fall is plotted versus latitude. The relationship is inverse and linear, with a maximum level of over 11 t/ha at the Equator declining steadily to a little less than 1 t/ha a t latitude 65" N in Europe, where forest grades into tundra. Fig. 1 reveals that litter production in central and north European forests is about the same as that of similar Cool Temperate forests in
129 the northern U.S.A. and Canada, although the European sites are on average about 10 degrees farther north. The warming effect of the Gulf Stream upon European climate is probably the major factor involved, but it is also possible that the intensive management of European as compared with North American forests is important in this connection. LITTER PRODUCTION I N FORESTS OF THE WORLD
2. Altitude and Exposure Ebermayer’s (1876) data for Fagus silvatica, Picea abies snd Pinus silvestris have been summarized by 200 m altitude classes from 250 to 1 250 m. This analysis, in Table XII, indicates a peak litter production at the intermediate elevations from 450 to 850 m, although no species covers the entire altitudinal gradient. The data for Picea are most complete, and show peak litter-fall between 650 and 850 m. There is a tendency in mountainous areas for rainfall and temperature conditions to be optimum for forest growth at intermediate elevations. At higher elevations, temperatures are too low and winds too severe for luxuriant tree growth, and at low elevations, there is often a decreased rainfall. Whether these conditions apply to the data in Table XI1 is not known. TABLEXI1 Litter Production and Elevation in German Porests Elevation
(4 250
650
1050
Fagua ailvatica Picea abies Pinw, silvestris (total litter, metric tons/ha/yr) 3.8
-
3.3
4.1
3.4
6.0t
5.9*
3.9
-
3.6
-
3.1t
1250
* One value.
t Two values.
Ebermayer’s material was also divided into four exposure quadrants, NE, SE, SW and NW. Values from cardinal points (N, E, S, W) were divided in half and assigned to each of the adjacent quadrants. The results of this analysis are given in Table XIII, and indicate a lower litter production in westerly than in easterly quadrants. The highest average litter production was on the NE slope, generally considered to be least exposed to the heating and drying effects of insolation ; while
130
J. ROGER BRAY AND EVILLE GOREAM
TABLEXI11 Litter Production and Exposure in German Forests* Total litter production, metric tonslhalyr
Exposure
Total no.
Fagus silvatica
Picea abies
Pinus silvestris
Mean
Mean weighted by no. of stands
4.1 4.4 3.9 4.1
4.7 3.7 2.5 3.6
4.0 3.7 3.8 3.6
4.3 3.9 3.4 3.8
4.3 3.8 3.2 3.7
NE SE SW
Nw
stands
14.5 10.0 15.0 23.5
* From data in Ebermayer f1876). the lowest average litter production occurred on the most exposed (SW) slope. The greater average exposure effect of SW as compared with SE slopes is presumably owing to maximum reception of insolation on SW slopes in the afternoon, when the air is warmest, driest, and usually clearest. Thus insolation and evaporation maxima tend to be greatest on SW slopes.
3. Soil Fertility The influence of site class on litter production, with special reference to soil fertility, is shown in Table XIV. Site class designations are the European “bonitat” grades of decreasing fertility from I to V. Table XIV generally shows decreasing litter-fall with a decline in site quality,
TABLEXIV Litter Production and Soil Fertility in German Forests Species
Pinus szhestris
Piceu abies Fagus silvatica
Authority
Site class
Total litter (metric tonslhalyr)
I 1-111 I11
3.0 3.2 2.0 2.2 1.0 3-8 3.0 3.5 4.4 2.5 3-9
Zimmerle, 1933* Danckelmann, 1887a Wiedemann, 1948* Danckelmann, 1887a Wiedemann, 1948* Zimmerle, 1949* Wiedemann, 1936* Dietrich, 1925* Danckelmann, 1887b Wiedemann, 1931* Danckelmann, 188713 ~~
m-v
V I I11 I 1-111 I11 111-V ~~
* Cited by EhwaId (1957).
.
LITTER PRODUCTION IN FORESTS OF THE WORLD
131
although for Pagus silvatica the data fiom nineteenth- and twentiethcentury authors require separate consideration. The data for Pinus silvestris provide the clearest indication of a site effect, with litter production on the poorest site (V) one-third that on the best site (I).The intermediate site class (111)produces two-thirds as much littgr as the best class. Data of Bonnevie-Svendsen and Gjems (1957) also indicate higher litter-fall on more fertile soils in Norway. Mean litter production for Larix spp. is 1-6 t/ha on iron-podzol and 2.8 t/ha on transitional and brown-earth soils. For Picea abies the corresponding figures are 2.0 t/ha and 3.2 t/ha respectively. 4. Soil moisture Litter data from Ebermayer (1876) for Pinus silvestris and Picea abies are shown in Table XV from mesic and dry soil moisture sites.
TABLEXV Litter Production and Soil Moisture in German Forests* Species
Pin- silvestris P i n w silvestris Picea abies Picea abies
Soil moisture
No. of sites
Total litter (metric tons/ha/yr)
Mesic
6 11 31 2
4.0
Dry
Mesic
Dry
3.5 3.8 2.3
* From data in Ebermayer (1876). The decrease in litter-fall from mesic to dry conditions is especially marked for Picea, a mesic species, and less noticeable for Pinus, which tends to occur more often on exposed dry sites.
c.
TREATMENT
1. Plantations and Native Forests Only one study (Ohmasa and Mori, 1937) gives sufficient data to allow comparisons of litter-fall in natural forest stands and plantations. I n both Chamaecyparis obtusa and Pinus densijiora there is no significant difference between mean litter-fall in plantaJion and forest. Investigation by Mitchell (private communication) of a variety of indigenous Malayan species yields a mean value of 8-7 t/ha for natural communities and 10.6 tiha for plantations, not necessarily of the same species. 2. Influence of Tree Density and Basal Area Within closed-canopy forests litter production appears to be little affected by differences in tree density, as shown in Table XVI. Com-
132
J . ROGER BRAY AND EVILLE GORRAM
TABLEXVI Litter Production and Tree Density Species
Authority
Fagw silvatica
Moller, 1945
Populus trernula
Sviridova, 1960
Pinus paluatris
Heyward and Barnette, 1936
Pinus ponderosa
Biswell and Schultz (P.c.)
Density (treeslha), 179 233 244 248 281 317 901 908 1173 5 842 6 732 988 1464 1688 2 460 889 1161 1 947 2 402 1196 1495 2 931 3 459
Litter (metric tons/ ham) 2.8 2.3 2.3 2.6 2.7 2.5 2.9 2.8 2.6 2.2 3.0 5.0 4.2 5.4 4.9 2.7 3.4 2.7 3.3 2.6 2.0 1.8 2.1
parison of eleven stands of Fugw silvatica (Moller, 1945) by a rank correlation test showed no significant correlation ( p>0.10) between litterfall and tree density. Similarly, studies by Sviridova (1960), Heyward and Barnette (1936) and Biswell and Schultz (Schultz, private communication) failed to show any consistent relationship between these two variables, although in each of these instances only four stands were compared. I n Norway Bonnevie-Svendsen and Gjems (1957) have shown a distinct correlation between annual fall of leaf litter and stand basal area in a series of Gymnosperm and Angiosperm stands. Litter-fall averaged about 70-75 kg per m2basal area, over a basal area range from 8 to 40 m2/ha. In Missouri (U.S.A.),Crosby (1961) has demonstrated a correlation between total litter-fall of Pinus echinata and stand basal area, but in this case an increase from minimum to maximum basal area coverage of three-fold only doubled the annual litter-fall. The stands of low basal area had been thinned a few years prior to litter collection, and presumably the less productive trees were removed.
LITTER PRODUCTION I N FORESTS O F THE WORLD
133
3. Effect of Thinning If a closed-canopy forest is thinned there is a decrease in litter production which is roughly proportional to the degree of thinning. Data in Table IV demonstrate this relationship for Pseudotszqa menziesii (Dimock, 1958), Picea abies (Wright, 1957) and Fraxinus excelsior (Boysen-Jensen, 1930). I n all cases the control stand has the highest litter-fall and the most heavily thinned stand the lowest. Moller (1945) has shown the effect of thinning upon the standing crop of Fagus silvatica leaves. With no thinning, leaf crop was 2.0 tiha, with Bregentved thinning 1.9 t/ha and with Vemmetofte thinning 1.7 t/ha.
4.'Effect of Litter Removal Rights to utilize forest litter still existed in Germany in 1954, particularly in Bavaria, where it sometimes caused extreme reduction of forest growth (Mayer-Krapoll, 1956). By comparing areas with and without rights to litter utilization, it has been estimated that annual forest output may require forty years to recover from long-continued litter removal. The loss of nitrogen in the litter is believed to be of especial significance in lessening forest productivity. Wiedemann ( 1951) presented data from study plots (Hermeskeil143,146, Table 363, p. 260) indicating that twenty-five years of litter utilization reduced basal area increase by about two-thirds. Thirty years were then required for recovery.
D.
THE TIME FACTOR
1. Seasonal Variation If forest litter is ever to be utilized economically, it will be of importance to know the pattern of litter-fall, whether distinctly seasonal, or more or less continuous. Such knowledge is also of the utmost importance to students of population dynamics in organisms responsible for litter breakdown, and may be of interest to persons concerned with the role of organic matter in soil development. The pattern of litter-fall varies greatly, as demonstrated by Figs. 2-5. I n the Equatorial forests of Ghana, Colombia and Malaya litter-fall is continuous throughout the year, but with a tendency for slightly greater deposition during the first half of the year. I n Ghana a, short dry season in January and February was noted as leading to increased leaffall (Nye, 1961). Laudelot and Meyer (1954) state that at Yangambi in the Congo there are two minima in the wet seasons and two maxima at the ends of the dry seasons. According to Deville (private communication) seven-year plantation of Acacia decurrens showed highs in
134
J. ROGER B R A Y AND EVILLE G O R H A M RAIN FOREST, COLOMBIA,
40
REP.
TOTAL
40
20
20 -I -I
2 !x
0
20
k J
O
2
40
.
0
.
RAIN FOREST, GHANA, TOTAL
40
w I-
.
40 20
.
(I)
.
( 2.)
0
UNDISTURBED DIPTEROCARP FOREST,
MALAYA,
TOTAL
40
20
20
(3)
0
n
w n.
3 I
40
5
20
=
o
0
.
o
40
.
.
.
.
.
SECONDARY FOREST, MALAYA,
.
.
.
.
.
TOTAL
40
20
.
.
.
.
.
.
.
.
.
.
.
SHOREA LEPROSULA [INDIGENOUS 1 PLANTATION, MALAYA
1 JAN.
(3)
0 40
20
20 0
0
(31
/
FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT.' NOV. OEC
0
FIG.2. Seasonal litter-fall in equatorial forests. (1) Jenny et al., 1949;1(2) Nye, 1961; (3) Mitchell (P.c.).
December (18% of total litter-fall) and June (llx), with lows in May (3%) and August to September (5% each). It should be noted that many individual species of indigenous tropical rain forest are distinctly deciduous, though not necessarily tied to any sort of annual cycle. The pattern and timing of leaf replacement is extremely variable, and dependent upon both external and internal factors (see Richards, 1957, pp. 193-8). I n the Warm Temperate forests of eastern Australia, Fig. 3 shows that litter-fall goes on throughout the year, but with a distinct maximum in spring and early summer (October to December). Precipitation generally increases along with temperature during this period in eastern Australia (Walter and Lieth, 1960). I n the Eucalyptus regnans forests of Victoria, Australia, Ashton (private communication) reports about nine times as much leaf-fallin summer as in winter. I n western Australia both young and old forests of Eucalyptus marginata deposit leaf litter mainly from January to March, the warm dry part of the year. Other litter falls irregularly throughout the year, but with slightly greater intensity at about the time of maximum leaf-fall (Hatch, 1955). Eucalyptus diversi-
LITTER PRODUCTION I N FORESTS OF THE WORLD
40
:AST
AUSTRALIAN
FORESTS,
136
LEAVES SCLEROPHYLL
20
2 a
40
w
20
5
0
2 a
40
I-
I-
W
20
0
: o a
3
I I-
z
0
E
0
0
-t
-t
40 20
O 40 20 0
I I R G l N EUCALYPTUS MARGINATA, WEST A U S T R A L I A
-
OTHER
PlNUS NIGRA,
NEW Z E A L A N D
LEAVES
P l N U S RADIATA, LEAVES
-.-,#'
.___-______ --0
NEW Z E A L A N D
40
OTHER
*A,
'---
...
,
A
- 20
(4)
I-
FIG.3. Seasonal Litter-fd in forests of the southern hemkphere. (1) Webb (P.c.); (2) Hatch, 1956; (3)Miller andHurst, 1957; (4) Will, 1959.
color in western Australia shows a similar pattern of litter deposition (Stoate, 1958). I n New Zealand the peak leaf-fall of Nothofagus truncata is connected with the development of new leaves in the spring months of October and November (Miller and Hurst, 1957). The main fall of non-leaf litter takes place 2 months earlier. For the exotic northern Gymnosperms Pinus nigra, P. radiata and Larix decidua in New Zealand, maximum needle-fall occurs in autumn (March to May), according to Will (1959). While precipitation is rather uniform, March is the driest month of the year (9.4 mm) and June the wettest (14.5 mm). Pseudotsuga menziesii shows no definite seasonal trend. I n all species the fall of non-needle litter is more affected by storms than is needle-fall, which does however show some storm influence. The main period of non-needle litter deposition is clearly mid-winter (June to July) for Pinus nigra, the peak coming about 2 months after cessation of needle-fall. The pattern is less regular for Pinus radiata, the average over 4 years showing one peak near the time of maximum needle-fall and another about 5 months later. The Warm Temperate forests of Tennessee in North America also
136
J . ROGER BRAY A N D EVILLE QORRAM
40
20
0 40
rENNESSEE FORESTS, TOTAL UPLAND PINUS
20
0
0 40
i
FINNISH FORESTS,
LEAVES
(
20
3)
LL 4
a
0
-
40
u
-I W
20
13
3 0 z a u Q
40
20
*- I I 0
I
0
40 20
'ICEA
ABlES SCOTLAND, TOTAL
--
DENMARK, LEAVES
------__-h
_ . I -
40
20,
SITCHENSIS,
WALES,
---_--_
LEAVES YEAR OF LOW L E A F F A L L
YEAR ' O F 4IGH L E A F F A L L
20
(6)
~.0
0 'ICEA
.40
'
.40
0 40
20 0
IAPANESE GYMNOSPERM FORESTS, PlNllS IENSIFLORA
LEAVES
CRYPTOMERIA
oOTUSA
.. AN.
FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
0
FIG.4. Seasonal litter-fall in forests of the northern hemisphere. (1) Witkamp and van der Drift, 1961; (2) Olson (P.c.); (3) Viro, 1955; (4) Kendrick, 1959 and Danckelmann, 1887; (5) Mork, 1942; (6) Wright, 1957 and Bornebusch, 1937; (7) Owen, 1954; (8) Ohmasa and Mori, 1937.
show a seasonal pattern, although some leaf-fall is observed throughout the year (Fig. 4). Angiosperms exhibit a distinct autumnal peak as the weather cools, while the seasonal effect is much less for Pinus echinata (Olsen, private communication). For Pinus echinata farther north in
137
LITTER PRODUCTION IN FORESTS O F THE WORLD
Missouri it is reported (Anon., 1960) that 60% of litter-fall occurs in the 3 months from September to November. I n Cool Temperate forests seasonal patterns of litter-fall are often striking (Fig. 4), with autumnal cooling leading to more or less complete leaf-fall in deciduous species, as shown by the graphs for Dutch Quercus and mixed Angiosperms, and for Finnish. Betula. I n New Hampshire (Anon., 1932) it is reported that four-fifths of the mixed Angiosperm litter-fall over the seven months June to December occurs in October. Among Gymnosperms the pattern of deposition ranges from distinctly seasonal, as in the various stands of Pinus silvestris represented in Fig. 4, to irregular throughout the year, as is the case with Picea abies in the stands shown. Chandler (1944) has noted however that Picea abies planted in the north-eastern U.S.A. shows distinctly lower needlefall in spring and summer than at other times of year. In contrast irregular collections by Lindberg and Norming (1943) in Sweden showed high rates of needle-fall during late spring and early summer. Picea sitchensis in Wales showed a rather irregular pattern of needle-fall whether the total for the year was high (1946-47, with a very cold winter) or low (1947-48). There was however a slight tendency for spring and autumn maxima. Such a bimodal spring and autumn pattern of needlefall was more strongly exhibited by Japanese stands of Cryptmeria japonica, Chumaecyparis obtusa and Pinus densijora. TABLEXVII Speci,fic Differences in Leaf Fall within an Upland Oak Porest in Tennessee, U.S.A. Leaf fall as per cent of total for each species Late August Overstory Understory Miscellaneous
Quercw velutina Quercus coccinea Cornus sp. Oxydendrum arboreum Nyssa sylvatica Quercw alba Quercw montana Quercus falcata Quercw stellata Aeer rubrum Carya sp. Pinw echinata
* Balance of 10% overwinters, 5 % ~
~
0 1 3 1 63 0 0 0 0
0 0 0
MidOctober 3 12 72 99 37
16 4
43
71 32 52 20
Early December 97 87 25 0 0 74* 96 57 29
68 48 80
~~~~
falling by February and the remainder by April.
138
J. ROGER BRAY AND EVILLE OORHAM
The difference in leaf-fall periodicity of different species within mixed forest has been shown clearly by Blow (1955), working in upland oak forest of eastern Tennessee in the U.S.A. Table XVII shows the percentage of leaf-fall during the year 1948-49 which was collected by late August, mid-October and early December. From this table it appears that the overstory species lose their leaves later than the understory species, and that even within these groups there are distinct specific differences. The only species in this forest which retains many leaves (10%) through the winter is Quercus alba, although a few remain REF
40
u. LK
W I-
t
40-
MALAYAN FOREST ANISOPTERA
M A L A Y A N FOREST,
SHOREA
SHOREA
LAEVIS
.
I
11)
.20
QUERCUS
N E T H E R L A N D S FOREST
I
.
- 40
20-
-3
40
+ 60 z
*
0
T R EM U L A
40
20
20 0
J A N . FEB. MAR. APR. MAY JUNE JULY
AUG. SEPT OCT. NOV. DEC.
FIG.5. Seasonal litter-fall of individual species in mixed forests. (1) Mitchell (P.c.); (2) Witkamp and van der Drift, 1961.
on Quercus stelbta. Apparently overstory species may lose their leaves earlier than understory species, or even understory individuals of the same species, in other areas, as for example in mixed savannah forest of NW Thailand (Ogawa et al., 1961). Pig. 5 shows the marked variation in litter-fall periodicity among mixed Angiosperms in the Netherlands (Witkamp and van der Drift, 1961). Populus tremula and Quercus robur show distinct peaks of litterfall in October and November respectively. Betula verrucosa also reaches a peak in October, but litter-fall is quite heavy in August and September as well. Alnus glutinosa is unusual in exhibiting a bimodal pattern, with many green leaves being shed in July in addition to the major fall of brown leaves in October. Tadaki and Shidei (1960) found that in a
139
LITTER PRODUCTION IN FORESTS O F THE WORLD
3-year-old Ulmus parvifolia stand, there was a decreasing attached leaf weight of from 438 g/mz on 20 May t o 297 g/m2 on 27 July. This decrease, which equaled 31% of the total leaf canopy by weight and was the result of a loss of all the lower and more shaded leaves, may be more typical of young sapling stands than of forests of adult trees. Individual species in Equatorial forests may also show seasonal variation, t o a lesser degree than in most Temperate forests but t o a, greater degree than the Equatorial mixed forest as a whole. rig. 5 shows a more or less bimodal pattern for three Malayan species, which may be compared with the data for whole Malayan forests in Fig. 2. 2. Annual Variation Total litter-fall may differ greatly in different years, as illustrated by data, in Table XVIII. Owing to variation in sampling procedures these TABLEXVIII Annual Variation of Total* Litter Production in Stands Sampled for Four or More Years (muximumlminimum ratios) Species EQUATORIAL FOREST Mixed secondary forest, Malaya EVERGREEN ANGIOSPERM Nothofqua trunmta, New Zealand DECIDUOUS ANGIOSPERMS Acer sacccharum mixed forest, Canada Popdua plantations. U.S.S.R. Quercua alba, Q. velutina, U.S.A. Betula, Norway Fagua silvatim, 30 to >90 yra, Germany GYMNOSPERMS EVERGREEN PiGea abies, Germany Picea abies, Norway Picea abies. Germany Pinua silvestris, Germany Pin- silvestris, Germany
Authority
No. yeam Max/& sampled litter-fall
Mitchell (P.c.)
4
1.1
Miller and Hurst, 1957
4
2.7
Bray Sviridova, 1960
4 4
1.8 1.1
Hole and Nielsen (P.c.) Mork, 1942
5 6
1.4 1.3
Ebermayer, 1876
7
1-3
Krutzsch, 1869 4 2.4 Mork, 1942 6 I -4 Ebermayer, 1876 7 1*5 Krutzsch, 1869 4 1-3 Krutzsch, 1869; Ebermayer, 1876 7 2.2 Pinua nigra, Austria Bohmerle, 1906 12 5.1 Pinua reainosa, U.S.A. Lunt, 1951 21 3.4 Pseudotsuga menziesii, U.S.A. Dimock, 1958 6 3.2 * In the few caaes where leaf litter was measuredseparatelyresults were similar.
140
J. ROGER BRAY AND EVILLE GIORHAM
values are not always strictly comparable, and it may be observed that for Angiosperms sampled over 4 years the ratio of maximum to minimum annual litter-fall may be as high as 2.7 (in a New Zealand Nothofagus truncata forest). The highest ratio for Northern Hemisphere deciduous Angiosperms is 1.8 for Acer saccharurn mixed forest. Records over 7 years yield no higher ratios. Data for Gymnospermsinclude some much longer periods of comparison, and the greatest annual variation is recorded for a Pinus nigra stand observed over 12 years, the maximum/minimurn ratio being 5-1. I n general the longer periods of observation yield higher ratios, as expected. Over comparable periods in the North Temperate zone, Gymnosperms tend to show high ratios a little more frequently than Angiosperms. It is well known that the longevity of evergreen Gymnosperm leaves depends upon both internal and external conditions, so that fluctuations from year to year in the environment might be expected to affect the leaf-fall of such species more than that of deciduous Angiosperms whose leaves are necessarily shed every year. The single 4-year ratio for Equatorial forest is very low, at 1.1, as might perhaps be expected where climatic fluctuations are not very severe. The fall of non-leaf litter has not often been measured over several years, but annual variation in the four recorded cases is relatively high, maximum/minimum ratios over 4-6 years ranging from 1.9 for Nothofagus truncata (Miller and Hurst, 1957) to 11.9 for Quercus forest (Hole and Nielsen, private communication). Bray recorded a ratio of 5.8 for Acer saccharurn mixed forest and Mork (1942) a ratio of 3.7 for Betub. Such wide variation is to be expected, since the fall of branches is a very local phenomenon of great weight where it occurs. Among environmental factors mentioned as associated with abnormal litter-fall are storms (Picea abies - Bornebusch, 1937; exotic Gymnosperms in New Zealand -Will, 1959; Betula - Knudsen and MauritzHansson, 1939), which may have a very great effect on twig and branch litter-fall. Insect attack may also be important (Picea abies - Mork, 1942). Dryness has been remarked as a factor in high Picea abies needlefall (Bornebusch, 1932), but in contrast Witkamp and van der Drift (1961) observed that in the Netherlands three surface-rooting deciduous species exhibited distinctly low litter-fall during a dry summer, while a fourth deep-rooting species yielded only slightly less litter than usual. I n New Zealand, Miller and Hurst (1957) reported that hot dry summers favor flowering of Nothfagus truncata, and since leaf bud production for the following year’s foliage varies inversely with flowering, a lower subsequent leaf-fall would be expected. Cold temperatures may also increase litter-fall, for Owen’s (1954) data on Picea sitchensis in Wales show nearly twice as much needle deposition in 1946-47, when the
LITTER PRODUCTION I N FORESTS O F THE WORLD
141
winter was extremely cold, as in the following year. Dimock (1958) also reported for Pseudotsuga menziesii in Washington state, U.S.A., that in the 10 months following a severe cold spell litter-fall amounted to nearly three times that of previous years. Viro (1955) in Finland found that the cold September of 1949 led to early leaf-fall in Betula, while the warm September of 1947 led to late leaf-fall. Mork (1942) has suggested that cool temperatures during leaf development may lead to a light litter-fall later.
3. Age of stand I n no case has litter-fall been followed through a generation in an individual stand, so that all studies of age effects have been based on diverse stands of different ages. The results of such studies are also rather diverse. For example, Danckelmann (1887b) found litter-fall in Fagus silvatica forests on good soils increased about 20% between 30 and 90 years, after which a slight decline was manifested, also evident in Hartig’s data for stands aged 80 to 120 years (cited by Ebermayer, 1876). On the other hand Ebermayer (1876) reported a trifling decline in litter-fall from 30 years on, and Moller (1945) found that standing crop of leaves varies rather little between young (31-60 years), medium (61-119 years) and old (120-200 years) forests, the crops averaging 2.8, 2.5 and 2.7 t/ha respectively. I n the case of Pinus silvestris Danckelmann (1887a) reported a very slight decline in litter-fall from age 30 on, while data from Voronezh in the U.S.S.R. (compiled by Sonn, 1960) showed a more striking drop, from 2.5 t/ha at age 20 to 1.3 t/ha at age 100. Ebermayer (1876) however recorded litter-falls of 2.9, 3.0 and 3.6 t/ha at ages 25-50,50-75 and 75-100 years respectively. For Picea abies Danckelmann (1887b) found maximum litter-fall to occur in middle age (60-80 years), while Ebermayer (1876) observed a steady decline from 4.5 t/ha in stands less than 30 years old to 2.8 t/ha in stands over 90 years old. If all the above-mentioned European data are graphed together and medians taken for successive intervals, little variation in litter-fall is evident from 30 to more than 100 years of age. It would appear that there is no inherent tendency toward higher or lower litter-fall with increasing age, once the canopy becomes closed, but that environmental conditions (including biological agents such as insects or fungi) exert a decisive influence. One additional Australian case may be of interest, in which Eucalyptus regnans stands of 25 years (height 27 m, density 1013 t/ha), 55 years (43 m, 217 t/ha) and circa 200 years (76 m, 47 t/ha) were examined by Ashton (private communication). Total litter-fall amounted to 6.1,
142
J. ROGER BRAY AND EVILLE GORHAM
7.2 and 7.2 t/ha for these three ages, and leaf litter to 3.2, 3.7 and 3.7 t/ha. Litter-fall was thus the same under the 55- and 200-year forests, despite a more than four-fold difference in density. However, undergrowth litter contributed about a quarter of the total litter collected beneath the 200-year forest and only about a tenth of that beneath the 55-year stand.
VI. STANDING CROP OF LEAVES A. SEASONAL CHANGES -INTRINSIC Olsen (1948) found no consistent dry weight change in leaves of Fagus silvatica after the rapid increase accompanying foliage maturation in May. The terminal value for yellow leaves prior t o defoliation was a trifle low, but cannot be specified accurately from his graph. Mitchell (1936) reported rather marked increases in leaf dry weight of six eastern American Angiosperm trees until the beginning of July (and in the two Quercus species until the beginning of August). Carya (Hicoria) ovata leaves in full autumn color weighed only a littlk less than green leaves sampled a month before. Tamm (1955) observed a spring phase of rapid dry weight increase in needles of Swedish Pinus silvestris and Picea abies, followed by a dry weight loss of about 20% in June and July. Viro (1955)sampled different age groups of needles of the same species in Finland during August, and found the dry weight of 1000 Pinus silvestris needles to be 28.6 g in the first year, 28.9 g in the second, 29.5 g in the third, and 34.4 g in older needles ranging up to eight years in age. For Picea abies needles the correspondingweights were 3.51,4-76,4*58and 5.02 g. Weight changes upon and immediately prior to abscission have been investigated by Viro (1955) in a comparison of dry weights of 1000 green leaves or needles collected in August with dry weights of 1000 yellow leaves or needles collected partly from the tree and partly from the ground at the end of September. Weight loss associated with yellowing averaged 21% (range 19 to 23%) for the deciduous Angiosperms Betula (pubescens and verrucosa), Populus tremula, Alnus incana and Salix caprea. If yellow Pinus silvestris needles are compared with needles older than three years, the yellow ones weigh 44% less. For Picea abies the difference is 39%. However, it cannot be assumed that all yellow needles are more than three years old. If yellow and three-year needles are compared, the weight loss on yellowing would appear to be only 34% for both Pinus and Picea. Such a weight loss would still be very high, about one-third of the total dry matter. A much lower difference between brownish and green Picea pungens needles was observed at Minneapolis, U.S.A., on 29 May 1963. Sixty-eight brownish needles were
LITTER PRODUCTION I N FORESTS OF THE WORLD
143
carefully plucked and trimmed along with the same number of immediately adjacent green needles, and a dry weight loss of only 13% was associated with browning. However, these brown needles were not quike ready to fall, for they required a distinct tug with forceps to pluck them. It was also apparent in this case that many needles remained long after abscission upon the branches beneath, where they had become trapped when falling. Presumably considerable weight loss might take place before such needles reached a litter collector. No data could be found for dry weight changes associated with abscission of Warm Temperate or Equatorial tree leaves. However, in 1962, leaflets were sampled from a small leguminous tree, Tamarindus indica, growing in the greenhouse of the Botany Department at the University of Toronto. This tree has compound leaves with from twenty to twenty-six opposite leaflets which yellow and drop off separately. Collections were made of leaflet pairs in which one leaflet was yellow, possessed a well-formed abscission layer, and dropped when lightly touched; while the opposite leaflet was green, healthy and fimly attached. Leaflets were washed with detergent to remove dust and other contaminants, and oven-dried at 80°C for 12h. The results of four leaflet collections from 2 March to 27 April showed the weight of yellow leaflets to vary from 77 to 84% of that of green leaflets, with a mean value of 81%. There was a slight tendency for the relative weight of the yellow leaflets to decrease as the season advanced and solar radiation and greenhouse temperature increased. On average, the Tamarindzls leaves appeared to lose nearly one-fifth of their dry matter before falling. I n another test on 23 May 1963, leaves were collected from a Ficus elastica tree growing in the greenhouse of the Botany Department at the University of Minnesota. A very few of the leaves were yellow, and fell when touched. Ten of these were collected along with immediately adjacent green and healthy leaves of closely similar size. Four 21 mm leaf discs were cut with a cork borer at random (but excluding the midrib) from each pair of washed leaves. The green and yellow leaves of each adjacent pair were superimposed so that disc locations would be the same, and two discs were cut with the green leaf on top, and two with the yellow leaf on top. Discs were then oven-dried a t 80' C overnight. The weight of the yellow discs was 81% of the weight of the green discs, indicating (as in the case of Tamarindus) that Ficus leaves lose nearly one-fifth of their dry matter just prior to abscission. It is interesting that results are identical for two leaves of such very different type, the leguminous leaves being small and rather delicate, the fig leaves large, leathqry and with a waxy surface.
144
J . ROGER BRAY AND EVILLE GORHAM
B. SEASONAL CHANGES - EXTRINSIC Estimates of the percentage utilization of attached leaves of forest trees by primary consumers range from 5.9% for an Acer saccharum Betula lutea - Fagus grandifolia swamp forest to 10.6y0 for an upland Quercus forest (Bray, 1964). The mean of leaf co&.umption values in Lindquist (1938), Rothacher et al. (1954) and Bray is 7.5%. The rate of consumption, decomposition and respiration occurring in leaves immediately after leaf-fall has seldom been studied. Lindquist (1938) estimated that 15% of Fraxinus leaf litter and 10% of Ulmus leaf litter were eaten by earthworms within 1 week after completion of leaf-fall. Loss of weight by respiration may also be high, especially before the leaf becomes desiccated. Studies of weight loss with various techniques of litter collection are badly needed, since such weight loss may be higher than is usually realized, especially when collections are made from the ground. There, leaves are subject to animal consumption, and also, if they remain moist, to microbial decay. Bocock et al. (1960) found that Quercus petraea leaves on a highly acid moder humus layer lost only about 10% of their dry weight in two months. The loss was about 13% on a faintly acid mull. Leaves of Fraxinus excelsior, much more susceptible to decay, lost about 26% of their dry weight in one month on the moder and about 43% on the mull. On the mull earthworms removed many whole Fraxinus leaflets from the nylon nets in which they were held. Lunt (1935) observed that in 7 weeks after leaf-fall the dry weight loss of some eastern North American Angiosperm tree leaves ranged from 3 to 12%, being low for Quercus alba and Fagus grandifolia, and high for Acer rubrum and Cornus jiorida. Earthworms were excluded from the samples by the fine cloth mesh beneath the flat boxes in which the leaves were placed.
c. MAGNITUDE
OF LEAF CROPS
Table XIX shows weights of all attached leaves in various forests, collections being made during the period of maturity but preceding the phase of defoliation. Data are on an annual production basis, to allow comparison of Angiosperms and Gymnosperms. The magnitude of these values for yearly leaf production is similar to that of the cold temperate leaf litter data in Table IV, but variability in site conditions, plant populations and growing season climate makes direct comparison dificult. I n view of the extrinsic and intrinsic losses between the period of petiole attachment and of collection in litter traps, it is likely that the leaf crop values in Table XIX are somewhat higher than litter values for the same community. Direct studies of leaf production and leaf litter within one forest are needed.
TABLEXIX Dry Weight of Xtunding Crops of Leaves on an Annual Production Basis* Authority
Location
Lat. Long. ~~
Bartholomew et al., 1953
Congo, Yangambi
Jacobs, 1936 Burger, 1947 Moller, 1945 Burger, 1947 Zemljanickii, 1954 Ovington, 1962 Potts, 1939 Rothacher et al., 1954
Southern Australia Switzerland, Adlisberg Denmark Switzerland, Winterthur U.S.S.R., Zavetnoe and Kamyshin U.S.S.R. U.S.A., Saugus, Mass. U.S.A., Tennessee
Ovington, 1962 Bray, unpublished
U.S.A., Bethel, Minn. U.S.A., Bethel, Minn.
U.S.A., San Dimas Forest, California Tadaki and Shidei, 1960 Japan Switzerland, Aarburg Burger, 1940 Denmark Mhller, 1945 Boysen-Jensent Denmark Denmark Tadaki and Shidei, 1960 Japan Denmark Mhller, 1945 Jokela and Yliinen, 1956 Finland Ovington, 1962 N. Sweden Ovington, 1962 U.S.S.R.
Kittredge, 1944
1N
56N 47N 47N 43N 45N 46N
Plant community
Age (yr)
~
6 24E Musanga cecropioides pioneer forest Musanga cecropioides pioneer forest 8 Musanga cecropioides pioneer forest 17-18 Evergreen Eucalyptus giganteu forest Quercus robur 13 50 12E Quercus robur 9E Quercus robur - Fagus silvatica forest 65 43E Quercus robur - Fraxinus pennsylvanica 17 shelterbelt Quercus forest 22-200 71W Quercus forest Quercus forest, heavily cut 15 yrs before sampling 93W Quercus forest 57 93W Quercus ellipsoidalis - Q. alba closed forest 62 Quercus elliwoidalis open forest 43 Quercus ellipsoidalis -Q. macrocarpa savannah 60 Quercus chrysolepis 55
35N 136E Quercus mongolica v. grosseserrata 47N 8E Fagus silvatica Fagus silvatica Fagus silvatica Fraxinus excelsior 35N 136E Fraxinus rnandshurica Betula verruco8a Betula verruwsa, B e t d a alba Betula verrucosa Betula vemucosa
* All oven-dried except the U.S.S.R. t From Tadaki and Shidei (1960).
(air-dried) and possibly the Finnish semplee.
80 40
25 26 20-40
Leaf crop (metric tonsblur) 5.6 5.4 6.4 4.4 5.3 4.0 3.1 3.0
3.1 2-6 3.8
3.5 5.2 2-1 0.8 4.1 2.7
3.2
2-7 3-1 2-7 2.2 3.3 2.0 2-7 3.6
TABLEXIX - continued Authority
Ovington and Madgwick, 1959 Ovington, 1962 Tadaki et al., 1961 Tadaki and Shidei, 1960 Bray and Dudkiewicz, 1963 Bray and Dudkiewicz, 1963 Satoo et al., 1956 Auten, 1941 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Tadaki and Shidei, 1960 Ovington, 1957
Location
Lat. Long.
Plant community
England, Peterborough
53N
Japan Japan Japan U.S.A., Itasca, Minn.
Betula maximowicziana 43N 144E Betula platyphylla 35N 136E Betula ermanii 47N 95W Populw tremuloidee closed forest
Canada, Dorset, Ontario
45N
Japan, Hokkaido U.S.A., Illinois or Indiana
43N 40N
Japan Japan Japan Japan England, Brandon
35N 35N 35N 35N 52N
Kittredge, 1944
U.S.A., Stanislaus National Forest, California Maruyama and Satoo, 1953 Japan, Makibori, Iwate Mork, 1942 Norway, Hirkjolen Burger* Switzerland Shibamoto* Japan
38N 40N 62N
OW Betula verrucosa
79W Populua tremuloidea - Populua grandidentaka open forest 143E Populua davidiana: 88W Robinia pseudacacia on old field Bassafras albidum on old field 136E Alnus hirsuta 136E A l n w hirsukz v. sibirica 136E S a l k gracilistyla 136E Salix vulpina 1E Pinua dveatris, plantation Pin- silvestris, natural regeneration P i n w nigra, plantation P i n w ponderosa 120W 88W Pinua densiJora forest 10E Picea abies Larix decidua Larix leptolepis
*From Tadaki and Shidei (1960).
Age
(Yd
24-55
Leaf crop (metric tonslhalvr) 1.7
41
2.2 1.2 2.4 3.8
39
1.6
25-40 9 12
2.2 2.9 2.8 2.6 2.6 3.5 2-3 2.9 3.9 3.7 2.0
10
3-55 11-14 31 65-69 40
1.7
0.8 2.6 3.3
LITTER PRODUCTION IN FORESTS OF THE -WORLD
147
The mean leaf crop in t/ha/yr for closed canopy Angiosperm forests in Table XIX is 3.7 for eleven Quercus sites, 3.0 for three Fagus sites, 2.9 for two Salix sites, 2.6 for two Alnus sites, 2.5 for two Fraxinus sites, 2-5 for three Populus sites, and 2-4 for eight Betula sites. The high values for Quercus sites, which range from 2.6 to 5.3 t/ha and include four studies with values of 4-0 t/ha or more, are noteworthy. The Quercus leaf is usually thick and leathery, with a high lignin content (see Handley, 1954, Table XII). It is possible that Quercus forests are among the highest pPoducers of leaf litter within the Temperate regions; and the thick soil litter layers frequently found in Quercus forests may be related to high production of leaves as well as to the slow rate of leaf decay of many species in this genus. Some of the Betula and Populus data &retaken from more northerly areas of the Temperate zone, and are not directly comparable with the Quercus values. Leaf crops of Gymnosperms in Table XIX are similar to those of Angiosperms, with means in t/ha/yr of 2.8 for five Pinus sites and of 3.0 for two Larix sites. Of the nine Angiosperm and Gymnosperm genera with two or more sites, seven genera, including both Gymnosperm genera, have leaf crops between 2.5 and 3-0 t/ha/yr. Mean Angiosperm leaf production by genera is 2.8 t/ha/yr which is similar to the Gymnosperm mean of 2.9 t/ha/yr.
VII. LEAFLITTERAS AN INDEXTO NET PRODUCTION Although leaf litter represents an amount somewhat less than leaf production, owing to intrinsic and extrinsic weight losses prior to and probably also following abscission, it may still be useful as a guide to minimum levels of total net production. There is a logarithmic relationship between the foliage weight of some needle-leaved and a few broadleaved trees and tree stem diameter (Kittredge, 1944; Cable, 1958; Satoo, 1962). It is doubtful if this relationship is of much use in predicting net total production since (1) the constants in the regression equation obtained for a given stand will not, because of varying modes of competition, necessarily apply to other stands of the same species (Satoo, 1962) and (2) the relationship does not apply over the entire life-span of a tree since it is common for many Gymnosperms, including Pinus banksiana and P. contorta, to have a reduced, scraggly, broomshaped crown in later years, which is much smaller than the crown in the earlier part of the life span. Cooper (1960) demonstrated a linear relationship between needle air-dry weight and growth of stem basal area from stump sections in two plots of young (30 yr and 49 yr) Pinus ponderosa. There was no statistical difference in the regression equation for the two plots. Other studies of foliage in relation t o net production are desirable to determine whether a general regression equation can be
TABLEX X Net Leaf Production in Relation to Net Non-leaf Production* ~~
~
Authority
Species
Total
Leaf
Stem
(metric tons /ha/yr) Polster, 1950 Ovington, 1957 Ehwald, 1957 (data of Zhmerle) Polster, 1950 Moller, 1945 Ehwald, 1957 (data of Zimmerle) Polster, 1950 Polster, 1950 Polster, 1950 Moller et al., 1954 Ehwald, 1957 (data of Dieterich) Ovington and Madgwick, 1959 Polster, 1950 Ovington et al.. 1963 Polster, 1950 Satoo et al., 1956 Bray and Dudkiewicz, 1963 Moller, 1945 Nye, 1961 Bartholomew et al., 1953 Means
Below ground
Pinua silvestris Pinus silvestris Pinua mXvestria
9.4 12.4 8.8
1.5 3.3 3.0
6.3 7.2 4.6
( 1.6) 1.9 1.2
Picea abies Picea abies Picea abies
14.2 15.6 14.8
2.1 2.7 3.7
9.7 (10.4) 9.0
(2.4) (2.5) 2.1
Pseudotsuga rnenziesii Larix europaea Fagus silvatica Fagus silvatica Fagus silvatica
17.5 14.2 14.2 11.4 12.6
2.7 5.6 3.2 2.5 3.5
11-9 6.2 8.6 7.4 7.3
(2-9) (2.4) (2.4) 1.5 1.8
Betula verrucosa Betula verrucosa Quercus borealis Quercus robur Populua davidiana Populus trernuloidee Fraxinus excelsior Equatorial forest, Ghana Equatorial forest, Congo 7 evergreen Gymnosperms 10 deciduous Angiosperms 18 cold temperate forests 2 equatorial forests
9.0 8.6 9.1 10.4 7.8 10.9 10.9 24.3 31-5 13.2 10.5 11.7 27.9
1.7 2.0 3.5 2.4 2.2 3.8 2.7 7.0 9.5 2.7 2.8 2.9 8.3
5.1 5.2 4.1 6.3 4.3 5.3 6-7 14.7 19.2 8.4 6-0 7.0 16.9
2.2 (1.4) (1.5) (1.7) (1.3) (1.8) 1.5 2.6 2.8 2.1 1.7 1-9 2.7
* Figures in brackets were estimated (see text).
LITTER PRODUCTION IN FORESTS OF THE WORLD
149
derived which is applicable within species or taxonomic groups. It is likely that amount of foliage will be more easily correlated with current growth than with mean growth over the lifetime of a tree or forest. Table X X lists strdies from which leaf production can be compared to non-lea€and total net production. If below-ground production figures were lacking, a conversion factor of 0.2 times above-ground production was employed to estimate them (Bray, 1963). A value of 12.9 t/ha for stem plus below-ground production in Picea abies (Moller, 1945) was separated into 10.4 and 2.5.t/ha respectively by using the average ratio of stem to below-ground production in six Cool Temperate stands for which observed values were available. (The stand of Betula verrucosa on deep peat, sampled by Ovington and Madgwick (1959), was excluded because it fielded a widely aberrant ratio.) It is clear from Table XX that stem production (4.3 to 19-2 t/ha/yr) exceeds leaf production (1.5 to 9.5 t/ha/yr), which in turn exceeds root production (1.2 to 2.9 t/ha/yr). Total annual production ranges from 7.8 t/ha in a Japanese stand of Populm davidiana to 31.5 t/ha in a Congo forest. A summary of relative litter production by climatic zones together with various indexes of net total production is shown in Table XXI, with Arctic-Alpinevalues being taken as unity in the f i s t three columns, and Cold Temperate values in the last three columns. Bole production was estimated from data in Paterson (1956) by determining the range of C W (climate-vegetation-productivity) indexes for the climatic areas of the stands summarized in Table IV from Tables 16, 17, 18, 19, 20 and 21 of Paterson as follows: Arctic-Alpine,, CVP: 25-100; Cold Temperate, CVP: 100-500; Warm Temperate, CVP: 500-ca 3 000; Equatorial, CVP: 3 000-20 000. Mean bole production in m3/ha calculated from Table XXII of Paterson was 2.0 for Arctic-Alpine, 5.5 for Cold Temperate, 10-3 for Warm Temperate and 14.0 for Equatorial forest areas. Relative bole production for the four climatic areas was 1 to 2.7 to 5-1 to 7.0, which was similar to the ratios for leaf litter of 1 to 3.6 to 5.1 to 9.7, although the relative range for bole production from Arctic-Alpine to Equatorial forest was less than the range for leaf litter production. The other relative production values summarized in Table XXI are for Cold Temperate and Equatorial forest only, and show a range of from 2.3 to 3.0 (mean 2.6) for Equatorial forest over Cold Temperate values. Litter production of Equatorial forest varies from 2.7 (leaf litter) to 3.1 (total litter) times Cold Temperate litter production, which indicated that the use of litter data t o predict total production would slightly overestimate the differencein production between Cold Temperate and Equatorial forest. The ratios in Tables XX and XXI indicate that Equatorial forest is around two to three times as productive as Cold Temperate forest ; that Warm Temperate forest productivity F
C.E.R.
TABLEXXI Relative Litter, Bole and Total Organic Matter Production in Four Major Climatic Zones Total litter (from Table XI)
Leaf litter Bole production Total production Total broad-leaved Total needle-leaved tree production tree production (from (from (from (from Becking, 1962) (from Becking, 1962) Table XI) Paterson, 1956) Table XX)
Arctic-alpine*
1.o
1.0
1.0
-
-
-
Cold temperate?
3.5
3.6
2.7
1.0
1*o
1.0
Warm temperate
5.5
5.1
5.1
-
-
-
10.9
9.7
7.0
2.3
3.0
2.4
Equatorial
* Taken as unity in the firat three columns.
7 Taken aB unity in the last three columns.
151
LITTER PRODUCTION IN FORESTS OF T E E WORLD
is nearer t o Cold Temperate than to Equatorial forest productivity, and that Arctic-Alpine forest is less than half as productive as Cold Temperate forest.
TABLEXXII Ratios of Total, Non-leaf and Stem Production to Leaf Production Total Leaf
~~
Non-leaf Leaf
Stem Leaf ~
Cool temperate evergreen Gymnosperms Cool temperate deciduous Angiosperms Equatorial forest
4.9
3.9
3.1
3.7 3.3
2.7
2.1 2.0
2.4
Ratios of total net production, non-leaf production and stem production to leaf-production are given in Table XXII, for evergreen Gymnosperms and deciduous Angiosperms in the Cool Temperate zone and for Equatorial forests. It is evident that the Gymnosperms exhibit the highest ratios, and the Equatorial forests the lowest. The apparent lower efficiency of tropical tree leaves in producing non-leaf material probably reflects a high rate of respiration (relative to rate of photosynthesis) under higher tropical temperatures. The higher efficiency of temperate Gymnosperm as compared with Angiosperm leaves in producing non-leaf material may be owing to their much longer period (more than two years) of contribution to net production. The significance of the ratios in Table XXII is di%cult to assess because of the small number of studies available. Further productivity research is needed, especiallyin tropical and warm temperate forests, and until such work is done our estimates of net forest production cannot be securely founded. If the ratios of non-leaf to leaf production are approximately correct, then a comparison of them shows that leaf litter cannot be employed directly as an index to net forest production, since evergreen Gymnosperm leaves produce annually over 40 % more non-leaf material than do deciduous Angiosperm leaves, and over 60% more than Equatorial forest leaves. The use of leaf litter values as production indices would therefore greatly overestimate Equatorial forest production and underestimate production by evergreen Gymnosperms. The Cool Temperate Gymnosperms are about 25% more productive than the Angiosperms (13.2 t/ha as against 10.5 t/ha in Table XX). The evergreen nature of the Gymnosperm trees (allowing photosynthesis whenever temperatures are suitable), and the great weight of canopy carried (with several years’ needles present), are presumably responsible for their comparatively high levels of production. Ovington (1956) has
152
J. ROGER BRAY AND EVILLE GORHAM
found that in English forest plantations Gymnosperms may be several times as productive as Angiosperms on the same sites. I n a general comparison over wide areas, however, the tendency of Angiosperms to occur on better soils than Gymnosperms may lessen the differences in production brought about by differences in canopy weight and duration. REFEBENCES Aaltonen, V. T. (1948). “Boden und Wald”, 457 pp. Berlin and Hamburg: Paul Parey. Alway, F. J., Methley, W. J. and Younge, 0. R. (1933).Soil Sci. 36, 399-407. Distribution of volatile matter, lime and nitrogen among litter, duff, and leaf mold under different forest types. Alway, F. J. and Zon, R. (1930).J. For. 28, 715-727. Quantity and nutrient contents of pine leaf litter. Andersson, S. 0. and Enander, J. (1948). Svenska SkogsvF&en. Tidakr. 46, 265-270. Om produktionen av lovforna och dennas sammansiittning i ett mellansvenskt aspbesthd. AndrB, P. (1947). Svenska SkogmForen. Tidskr. 45, 122-131. Bamkens och mossornasfornaproduktion i ett barrskogsbest&nd. Anonymous (1932). Bull. N.H. agric. Exp. Sta. no. 262. Formation of forest soils: rate of deposition of litter. Anonymous (1960).Rep. cent. St. F o r . Exp. Sta., p. 12. Auten. J. T. (1941). Tech. Notes cent. St. For. Exp. Sta. 32, 9 pp. Black locust, pines and sassafras as builders of forest soil. Bartholomew, W. V., Meyer, J. and Laudelot, H. (1953).Publ. INEAC Ser. Sci., 57, 27 pp. Mineral nutrient immobilization under forest and grass fallow in the Yangambi (BelgianCongo) region. Becking, J. H. (1962).I n “Die Stoffproduktion der Pflanzendecke” (ed.H. Lieth), pp. 128-131. Stuttgart: Gustav Fischer Verlag. Ein Vergleich der Holzproduktion im gemiissigten und im tropischen Klima. Black, J. N. (1956). Arch.. Met. Wien, Ser. B, 7 , 165-189. The distribution of solar radiation over the earth’s surface. Blow, F. E. (1955).J. For. 53, 190-195. Quantity and hydrologic characteristics of litter under upland oak forests in emtern Tennessee. Bocock, K. L., Gilbert, O., Capstick, C. K., Twinn, D. C., Waid, J. S. and Woodman, M. J. (1960).J. Soil Sci. 11, 1-9. Changes in leaf litter when placed on the surface of soils with contrasting humus types. Bohrnerle, K. (1906). “Die Streuvemuche im grossen Fohrenwalde”. 22 pp. Vienna: W.Frick. Bonnevie-Svendsen, C. and Gjems, 0. (1957).Medd. Norske Skogsfors~ksv.48, 111-174. Amount and chemical composition of the litter from larch, beech, Norway spruce and Scots pine stands and its effect on the soil. Bornebusch, C. H. (1937). pOr8tl. Fors0bv. Danm. 14, 173-176. Iagttagelser over rpldgranens naalefald. Boysen-Jensen, P. (1930).Forstl. Forsoksv. Danm. 10, 365-391. Undersogelser over Stofproduktionen i yngre Bevoksningeraf Ask og Bog. 11. Brauns, F. E. and Brauns, D. A. (1960). “The Chemistry of Lignin”, Suppl. Vol., 804 pp. New York and London: Academic Press.
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