Litter dynamics in khasi pine (Pinus kesiya Royle ex Gordon) of North-Eastern India

Forest Ecology and Management, 10 (1985) 135--153 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

135

LITTER DYNAMICS IN KHASI PINE (PINUS K E S I Y A R O Y L E EX. G O R D O N ) OF N O R T H - E A S T E R N INDIA

ASHESH

KUMAR

D A S and P.S. R A M A K R I S H N A N

Department of Botany, School of Life Sciences, North-Eastern Hill University, Shillong 793014 (India) (Accepted 21 M a y 1984)

ABSTRACT

Das, A. and Rarnakrishnan, P.S., 1985. Litter dynamics in khasi pine (Pinus kesiya Royle ex Gordon) of north-eastern India. For. Ecol. Manage., 10: 135--153.

Kumar

Seven-, 15- and 22-year-old khasi pine plantations (Pinus kesiya Royle ex Gordon) at Mawlai (1250 m) in Meghalaya, north-eastern India, produced 6663, 8090, 8984 kg ha-' year-' respectively of total litter. Needle litter varied between 78 and 98% of the total with a m a x i m u m in the 7-year-old plantation. Litter fall occurred throughout the year with peak fall during the drier months of March and April. Differences in concentration of N, P and K for needle litterwere observed throughout the year; Ca and Mg, however, showed very littlechange. Needle litter decomposition showed fast rates with rate constants (k) of --0.46 year-' for 1 year and --0.78 year-' for 2 years. A n exponential relationship was developed between needle litter decomposition and time. Release of elements during decomposition showed considerable variation, with K showing rapid release followed by Ca, Mg, P and N. Data on forest floor nutrient dynamics also showed greater residence time for N and P and a lower turnover rate for these two elements. The C O 2 evolution from the forest floor showed higher values during monsoon months, and lower values during winter months. The significance of higher litter production, along with faster rate of decomposition and release of elements under Pinus kesiya, compared to other pine species of the world is discussed.

INTRODUCTION

Litter fall and litter decomposition are two important processes determining the functioning of a forested ecosystem. The amount, composition and subsequent decomposition of litter is of major importance in studies of energy flow, nutrient cycling and primary production (Ovington, 1962; Newbould, 1967). The litter on the soil surface acts as an input-output system and is important in the nutrition of woodlands, particularly of those on soils of low nutrient status where the trees rely to a great extent u p o n the recycling of litter nutrients. In recent years, much emphasis has, therefore, been placed on determining the nutrient flux accompanying litter fall and decomposition (Scott, 1955; Carlisle et al., 1966; Gessel and Turner, 1976; Lousier and Parkinson, 1976; Maclean and Wein, 1978). 0378-1127/85/$03.30

© 1985 Elsevier Science Publishers B.V.

136

Most of the studies relating to conifer litter dynamics to date are available from the higher latitudes. Pinus kesiya Royle ex Gordon is a highelevation early successional endemic tree species, restricted to north-eastern India and found at an altitude of 800--1900 m in Meghalaya. The conifer forest represented by P. kesiya is different from others in being subjected to heavy rainfall chiefly confined to the m o n s o o n months, with high insolation during the rainless period. Thus, the study of litter dynamics is of interest from the point of view of the pattern of these processes in this subtropical-subtemperate pine species. STUDY A R E A

The study area is located in Meghalaya in Mawlai, 15 km north of Shillong (25°47'N latitude and 91°56'E longitude) and 1250 m above sea level. The soil is a reddish brown loam of lateritic origin. The pH ranges from 5.9 to 6.2. The climatic data for Shillong are shown in Fig. 1. Heavy rainfall is received from May to September during the monsoon. This period is characterized by higher maximum and minimum temperatures. The rest of the year (October--April) has only 525 mm o u t of the total annual rainfall of 2149 ram. The winter extends from November to February with a mean m a x i m u m temperature of 18.4°C and mean minimum of 12.1°C. March and April represent a relatively dry summer.

500

400 E E 300

30~ O o

%

2o

200 ¢@

Q.

100

J

F

M

A

M

J J Months

A

S

0

Fig. 1. Climate of Shillong (1977), e, m a x i m u m o. rainfall.

N

D

temperature; o, m i n i m u m temperature;

137 METHODS OF STUDY

Litterfall Three even-aged plantations (7, 15 and 22 years old) were selected for studying litterfall. An area of 2500 m 2 was demarcated in each plantation for litterfall studies. Wooden frames (1 m × 1 m) were used as litter traps (Newbould, 1967). Six litter traps were randomly placed in each study area. Monthly estimation of litterfall was made by collecting the litter and then sorting it out into four categories: (i) brown needle, (ii) green needle, (iii) cones, bark, and (iv) small branches. The litter so collected was then oven
Litter decomposition Litter decomposition was studied using the nylon bag technique. The bags were of 1-mm nylon mesh, 20 cm × 20 cm in size. Five g of air-dried needles (4% moisture content) were placed in each bag and the bags were placed on the forest floor. Three bags were removed at bimonthly intervals. At each sampling time, retrieved bags were returned to the laboratory, extraneous material was removed and the wet weight of the material measured. The material was reweighed after oven
C02 evolution from the forest floor To assess the metabolic activity associated with the decomposition process, estimates were made of CO2 evolution from the forest floor following the m e t h o d given by Walter and Haber (1957). Absorption of CO2 was measured in 50 ml of a 1 M KOH solution kept in a beaker under an inverted metallic box (5071 cm 3) for 24 h. For estimating soil respiration, the box was pressed onto the soil surface after removing the litter layer. In both cases, the box was additionally sealed with soil around the lower margin. The experiment was run in triplicate. The absorbed CO2 was estimated titrimetrically using 1 M KC1, with phenolphthalein as indicator. The data are presented as CO2 evolved and are expressed as mg m -2 h -1. Soil and litter temperature and moisture contents were recorded at monthly intervals.

138

Chemical analysis For chemical analysis, plant samples were ground and passed through a 70-mesh sieve. Nitrogen was determined by a semi-microkjeldahl procedure using a selenium catalyst (Bremner, 1960). Phosphorus and cations (K, Ca and Mg) were determined after dry-ashing at 450°C for a b o u t 2 h. Test solutions were prepared from a dilute hydrochloric acid extract of the ash after preliminary removal of silica b y a process involving dehydration. Phosphorus was determined colorimetrically by the m o l y b d e n u m blue colour m e t h o d (Peach and Tracey, 1956). Potassium was determined flamephotometrically (Allen et al., 1974). Calcium and magnesium were determined titrimetrically by EDTA titration using Eriochrome black T (EBT) and Reader's and Patten's reagent as two indicators (Allen et al., 1974). To study the residence time (Tn) and fractional annual turnover of nutrients, five replicates of forest floor materials comprising the L F H zone (litter layer + F horizon + H horizon) were sampled from three plantations using 50 cm × 50 cm quadrats. Samples were oven
Forest floor nutrient pool Annual litterfall nutrients

Fractional annual turnover = (1/Tn) X 100 RESULTS

Litterfall Table I shows the annual production of the different components of litter of P. kesiya in three age categories. The total amount of litter produced by a 22-year-old plantation was 8984 kg ha-' year-' and decreased in younger plantations. Needle litter comprised about 98% of the total litterfall in a 7-year-old stand. This percentage decreased with increased stand age. Conversely, production of litter components other than needle production increased in older plantations. Table II shows m o n t h l y variation in litter fall in 7-, 15- and 22-year-old stands. Different categories of litter reached maximum values at different times of the year. Brown-needle litterfaU t o o k place throughout the year b u t reached a maximum during t h e dry winter and summer months, as is typical for a 22-year-old stand. However, this pattern was less marked in younger stands, though maximal fall in all stands occurred during March and April. Green-needle litterfall occurred only at certain times of the year and was highest during the rainy months of July and August. Green-needle

139 TABLE I Annual litterfall in three plantations of P. kesiya Stand age Annual litterfall(kg/ha) a (years)

7 15 22

Brown needles Green needles Cones, bark, Dead branches Total etc. 6 3 8 3 ± 482 (95.80) b 6632 ± 596 (81.98) 6908 ± 580 (76.89)

144± 1 5 (2.16) 130 ± 18 (1.61) 111 ± 14 (1.24)

73± 14 (1.09) 268 ± 30 (3.32) 376 ± 44 (4.19)

8 3 ± 25 (1.25) 1082 ± 99 (13.39) 1551 ± 190 (17.28)

6 6 6 3 ± 484 (100.0) 8090 ± 663 (100.0) 8984 ± 746 (100.0)

a± Standard error (95% confidence limits). b Figures within parentheses indicate percent of total litterfall.

litterfall was totally absent during December--April. Cone fall in older plantations occurred during M a y - O c t o b e r , March and April, with male cones falling chiefly during the latter period. In a 7-year-old stand the cone fall was erratic b u t maximal fall of 2 kg ha -1 of female cones was observed in May. In March, 17.5 kg ha :1 conefall was exclusively due to male cones. Branch litterfall in 15- and 22-year-old stands coincided with peak needle fall and occurred only during May, June and February--April. The branch litterfall was erratic in a 7-year-old stand. The concentration of nutrients in needle litter showed considerable variation throughout the year (Fig. 2). Starting in May, the concentration of nitrogen and phosphorus increased, reaching a maximum in July and remaining steady at a lower level during the next few months, with an increase again starting in March of the following year. Calcium and magnesium on the other hand had slightly higher values during May and in subsequent months remained steady at a somewhat lower level. In general, the concentration of all nutrients was lower in older plantations and highest in the youngest one during the entire study period. Since the monthly variation in nutrient concentration of the green needles, dead branches and cones was not observed, only the average values for the entire study period are presented in Table III. It m a y be noted that green needles had higher (N, K and Mg) or more or less the same level (P and Ca) of different nutrients as the dead branches, whereas the cones had very low levels. Fig. 3 shows the m o n t h l y return of different nutrients to the forest floor through litterfall. While the return of nutrients occurred throughout the year, maximum return through litterfall occurred during February--April with a major peak during this period and a smaller peak during August-September. Table IV shows the total a m o u n t of nutrients returned to the forest floor during 1 year (May 1977--April 1978). The return was in the

140

~1 0

I I I I I I ~

~ 1 ~ 1

i i i~

~

0

I I I O0

0

I I I

0

0

IIllt

I f

~1 ~ <

il

141 order o f N > Ca > K > Mg > P. The return through brown needle litter was 80--85% o f the total a m o u n t of nutrients returned, the o t h e r components making up 15--20% (green needles, dead branches, cones). 1-00 ~' 0.5

z

0

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

!

I

I

I

I

I

I

I

!

I

I

I

I

I

I

I

I

i

l

I

I

I

I

i

l

( 08 •~ o L 10

~ ~04 0 c-

;a.

o

:~

0.60

c ~ 0"30 0

~

qa

~" 3 Z

0.8 E

O-4 0

I

i0"12 F

01

M J J A S O N D J 1977 Months

I

F M A

1978

Fig. 2. Nutrient concentration changes of brown needle litter of Pinus kesiya Royle ex Gordon, from May 1977 to April 1978. o, 7-year old; e, 15-year old; a, 22-year old.

Litter decomposition Dry weight loss o f pine needles due to d e c o m p o s i t i o n is shown in Fig. 4. Weight loss, which is expressed as a percentage o f the original dry weight, decreased exponentially with time. The equation may be given as Y = 104.376 e -°'°61~ (r = 0.961), where Y = p e r c e n t loss in weight and x =

142

~ 0

O 0

dN

O 0

od +1

~ 0

~o +1

O 0 +1

+1

O 0 +1

+1

N~4 do

~N +1

~d

o~ +1

dd

+t

i°

N~

+I

+I

+i

÷I

+I

+I

o~ +I

+I

+I

0

e~

O +I

+I

+I

+1

+1

+1

oo

oo +I

~

e~ 0II

•

°

.

•

°

o

dd +I

+I oo

oo

oo

0

O

+I

+I

+I

0

+t

+1

+1

0

oo

oo

÷I

0

o

.

•

°

°

oo +1

+1

+I

÷I

,~

e" O +L

•

e.,

+I

o o ~ a o •

e~ +1

O e~

8 [...

+1

+1

°

°

143 2G Nitrogen

15

2.0

)

Potassium

o 10.0!

Caicium

5.(]

Magnesium

~ 2-5

M

J

J

A ~.

5

O Months

N

D

J

F

M

A

;

Fig. 3. Monthly return of nutrients (N, P, K, Ca and Mg) through needle litter to the forest floor ofP. kesiya plantations, v, 7-year old; m, 15-year old; m, 22-year old.

decomposition time; e is the base o f the natural logarithm. Dry weight loss for the first year was about 37% of which 25% occurred during the first 2 months, June and July. No significant loss was observed between September and January. In the second year about 41% loss was observed, most of

144

which was during July--November. Thus, the cumulative loss for the 24m o n t h period was about 79%. Dry weight loss (%) along with decomposition constant k, as well as half time (t0.s0) and time to 95% loss of dry weight (t0.gs) a r e presented in Table V. The annual decomposition constant k was --0.46 year -1 for 1 year and --0.78 year -1 for 2 years. IO0 a

3=

\'~''"'~-~Y

_

104 • 376 • -0"061X ( r= 0-961 )

"O

.S

•

._~ t.. o 50

"%

I

i

0 2 4 (May 77)

I

I

6

6

I

I

.~

I

•

I

I

I

I

I

10 12 14 16 1~ 20 22 2/, Period (months)

Fig. 4. Needle litter decomposition of P. kesiya. Bars indicate 95% confidence interval. Solid line indicates cumulative weight loss; and broken line, transformed predicted weight loss based on negative exponential function.

TABLE V Dry weight loss and decomposition parameters of P. kesiya needle litter Decomposition time (months)

Dry weight loss (%)

ka

t0. s0

t0.95

12 24

37.5 79.2

0.46 0.78

1.50 0.88

6.52 3.84

ak, annual decomposition rate.

Changes occur in the concentration as well as the absolute quantity of different mineral elements during the course of decomposition as shown in Fig. 5. Expressed as a percentage of the original concentration, nitrogen showed a considerable fluctuation during the course of study but at the end o f 2 years it showed an increase from 100 to 136%. However, absolute nutrient mass declined gradually during the course of decomposition. In the first 12 m o n t h s about 68% of the total nitrogen mass remained in the litter

145

bag and this decreased to 29% after 24 months, indicating that 71% of nitrogen is released in 2 years. Phosphorus concentration also fluctuated during the study period but both concentration as well as absolute mass declined after 24 months. Only 10% of the original phosphorus in the litter bag remained after 24 months. Potassium, calcium and magnesium all showed a more or less similar trend of decline in concentration and absolute mass over the 2-year period. However, the initial rate of loss of potassium 150 " - ~ ,

~

__

I00

/ 0 ~

~0..o...~...~

o,

50

o Z 101

I

I

I

I

I

I

I

I

50

I

I

I

I

I

'

i

I

i

I

I

i

,

I

I

0

0 c 0

E c o u

._~ h-

,

10(3

0

100 5"

E 3

50 ~

50

3 E

3

3

~ so -..~,~

,o._.(~..~_~__o

"

u

o . . 0 . . . 0 . _ <). ..<). . .O

I

EI

0

I

0

50

0

I

I

I

~

i

'

'

'

'

i

I

10

I00

"

i

'

.

50

0 2 4 6 8 10 12 14 16 18 20 22 2/, May77 May79 Elapsed period (months) Fig. 5. Changesin the concentration and absolute amount of N, P, K, Ca and Mg during the decomposition of brown needle litter, o--o, concentration change;o---o, absolute amount.

146

was sharper and the final values obtained at the end of the study period were lower than those for calcium and magnesium. Increasing mobility of nutrients from decomposing pine needles was in the order: K > Ca > Mg >P>N.

C02 evolution from the forest floor The m o n t h l y variation in CO2 evolution from the forest floor is shown in Fig. 6. CO2 evolution from both litter and mineral soil was very low durioo[-

25

,~

u -

2O o..

t5 ~

E Q¢

40

300 -

lO ~

,C

20

5

0

I I I I I I I I I I I 0 2 3 4 5 6 7 8 9101112 May 77 A p r i l 78 Period ( M o n t h s )

O

•

0

: 200

~

100

I

I

I

I

I

I

I

I

I

I

1

2

3

4

5

6

7

8

9

10

May 77

I

I

11 12 April 78

Period ( Months ) Fig. 6. M o n t h l y v a r i a t i o n in CO 2 e v o l u t i o n f r o m f o r e s t floor. A, l i t t e r COs; o, soil CO 2. I n s e t figure s h o w s m o n t h l y v a r i a t i o n in soil a n d l i t t e r t e m p e r a t u r e a n d m o i s t u r e contents. A, l i t t e r ; o, soil; ~ , moisture content;-- -, temperature.

147

ing the winter months of November--February but increased considerably during the warmer part of the year. The peak period of CO2 evolution from the litter layer was in September and that from the mineral soil was in August. The inset figure shows the pattern of change in moisture and temperature conditions of litter and mineral soil during the year. CO2 release was related to moisture and temperature in such a way that it declined at low temperature and moisture levels. Although moisture content during March and April was low, there was a rise in temperature during these 2 m o n t h s favouring increased production of CO2. The forest floor nutrient mass of three stands is shown in Table VI. The relative abundance of nutrients in the forest floor was N > Ca > K > Mg > P. The nutrient mass tended to increase with the age of plantation. T A B L E VI N u t r i e n t c o n t e n t o f t h e f o r e s t floor o f t h r e e p l a n t a t i o n s o f P. kesiya

Plantation age (years)

Nutrient content (kg/ha) N P K

Ca

Mg

7 15 22

181.53 231.04 276.86

66.56 81.08 87.54

32.23 37.51 40.72

26.82 33.47 38.25

42.63 49.82 55.38

The residence time or turnover time of nutrients and fractional annual turnover values for different nutrients in three plantations (Table VII) varied considerably for mineral elements. Residence time for nitrogen and phosphorus was much higher and it was least for potassium; correspondingly, the annual turnover rate of the former two was the lowest. The mobility of different nutrients on the forest floor was in the order: K > Ca > Mg >P>N. T A B L E VII R e s i d e n c e t i m e a n d f r a c t i o n a l a n n u a l t u r n o v e r o f n u t r i e n t s o n t h e f o r e s t f l o o r o f P.

kesiya p l a n t a t i o n s Plantation age (years)

Residence time (years) N P K Ca

Mg

Fractional annual turnover (%) N P K Ca Mg

7 15 22

3.54 3.79 4.31

1.56 1.63 1.68

28.24 26.39 23.22

2.16 2.41 2.49

1.26 1.35 1.38

1.61 1.72 1.78

46.34 41.56 40.24

79.24 74.22 72.38

62.24 58.29 56.26

64.23 61.44 59.38

DISCUSSION

The present studies on the three stands of Pinus kesiya (7, 15 and 22 years of age) reveal an increasing trend in the production of needle and

148

non-needle litter as the stand ages, an observation also made by other workers (Wiegert and Monk, 1972; Cole et al., 1975; Gessel and Turner, 1976; Maclean and Wein, 1978), though some have reported a decreasing litter production after a certain age (Ebermayer, 1876; Zavitkovski and Newton, 1971). The total litter production in the present study was higher when compared with the world survey done by Bray and Gotham (1964) and that reported for a 25-year-old stand of Pinus roxburghii at Dehra Dun in western India (Subba Rao et al., 1972). However, Freezaillah {1966) observed 6178 kg ha -I year -1 of needle-litter production in a 5-year-old stand of Pinus caribaea in Malaysia which is comparable to 6690 kg ha -1 year -1 in a 7-year-old stand obtained during this study. Bray and Gotham (1964) have shown: (i) that an inverse relationship exists between the a m o u n t of total litter production per year and the latitude of the locality; and (ii) that leaf litter constitutes roughly 70% of total litter. From their graph (Fig. 7) total annual litter production for the present study should be 7200 kg ha -~ year -1, with 5040 kg ha -~ year -~ of needle litter. The observed value in the present study, however, showed a somewhat higher range (6663--8984 kg ha -~ year -~ for total litter and 6 3 8 3 - - 6 9 0 8 kg ha -~ year -~ for needle litter). This m a y be related to the more favourable temperature and rainfall conditions in the north-eastern hill region for a major part of the year with growth retardation occurring only for a b o u t 3 months during the dry winter. Faster growth rate in this early successional tree species with three flushes in a year and a shorter life-span of a b o u t 10 months for the needles {Das and Ramakrishnan, unpublished) may also contribute towards high litter production. 12

ed value (Total litter )

8 ..c

0

~"

6

o

4

=

2

0

I

I

I

I

10

20

30

~0

North

or South

I

I

60 Latitude (degrees)

50

",.I

70

Fig. 7. Annual production of total litter in relation to latitude (adapted from Bray and Gorham, 1964) and its comparison with the present study.

149

According to Bray and Gorham (1964), the litterfall pattern in gymnosperms may range from a distinctly seasonal to an irregular pattern throughout the year. The seasonal pattern of litterfall shown in the present study, with its peak during the months of March and April, may be related to the drier climate prevailing during t h i s period. Most of the green-needle litterfall recorded in the present study occurred during the rainy months, an observation similar to that of Bagnall (1972) in Nothofagus forest and which was attributed to severe storm conditions. Changes in the concentration of nutrients in needle litter was observed during the study period. Increased concentrations of nitrogen and phosphorus were observed during May--July which could be due to lesser retranslocation of these nutrients before abscission and also due to the addition of nutrients through precipitation, while residing in the litter trap. The comparatively low concentration of nitrogen and phosphorus during FebruarymApril may be due to greater re-translocation of these nutrients before major litter fall. Potassium, which is easily leachable, showed a lower concentration during MaymJuly; calcium and magnesium, which are immobile, showed little change in concentration throughout the year. The changes in the concentration of litter through the year have been observed by other workers (Malkonen, 1974; Lamb and Florence, 1975; Maclean and Wein, 1978). The total litterfall nutrient return in the present study showed higher values than similar studies done elsewhere (Table VIII). Greater nutrient returns in Pinus kesiya could be accounted for by greater litter production. Available data on litter decomposition of different pine species, as shown in Table IX, indicate that the first year's loss in dry weight of needle litter of P. kesiya is lower than that of P. taeda and P. sylvestris in a temperate climate, though other studies from similar climates showed much lower rates of decomposition. However, many of these studies were not continued for more than a year, although the importance of long-term studies for slowly decomposing litter like that of pines was emphasized recently by Fogel and Cromack (1977). Considering the rates over 2 years, the rate of decomposition was found to be higher for P. kesiya than in other similar studies. Temperature and moisture conditions are the two important abiotic factors controlling the rate of decomposition under natural conditions {Witkamp, 1966) both of which are very much favourable to P. kesiya. Thus, the rate of litter loss, which is higher during the monsoon months, as supported by the study on CO2 evolution, is indicative of favourable conditions for decomposition during this time of the year: higher temperatures and wetter soil moisture conditions. Changes in concentration and mass of nutrients occurred during the decomposition of needle litter. Although the concentration of nitrogen increased by 36%, the absolute nutrient mass decreased because the rate of weight loss was greater than the concentration increase. Such an increase in concentration of nitrogen was also reported by others (Coldwell and

150

u~ t'.-

u~ 0

e~ 0

c~

e~

u'~ u~

¢.,

~J 0

0

t

0 oO u~

t",-

0

e~.

0

0

I

I

t,~ t'.-

I

t~

c~

0

I I

0 0 ,..~

I d

00

0

e~ u~ u~

e.

I

I i

I e~

t-,-

I

I I

I c~ u~

T

e~

u~

Z

u~

.~

. ~

a:

0

z

151

T A B L E IX C o m p a r i s o n o f a n n u a l d e c o m p o s i t i o n r a t e in t h e p r e s e n t s t u d y w i t h d a t a f r o m t h e l i t e r a t u r e Location

Tree species

Decomposition time (months)

Dry weight loss (%)

ka

References

North Carolina (U.S.A.)

Pinus s t r o b u s

12

36.9

0.46

Cromack and Monk, 1975

12 12

44.0 48.0

0.58 0.65

T h o m a s , 1968 Hayes, 1965

12

24.5--29.9

0.307--0.355

Maciean and Wein, 1978

24 12 24 36 12 24

36.6--42.9 32.7 46.6 54.6 37.5 79.2

0,228--0.280 0,396 0.314 0.263 0.46 0.78

Tenessee (U.S.A.) P. taeda England P. sylvestris New Brunswick (Canada) P. banksiana

Finland

Pinus spP.

S h i l i o n g ( I n d i a ) P. k e s i y a

Mikola, 1960

Present study

ak, annual decomposition rate.

Delong, 1950; Will, 1967; Anderson, 1973; Howard and Howard, 1974) though Maclean and Wein (1978) reported increases in both concentration and absolute mass during decomposition of the needle litter of Pinus banksiana. The increased concentration of nitrogen during the decomposition of P. kesiya needle litter could be due to addition of nitrogen through precipitation. Potassium, being highly leachable, showed maximum loss, an observation also made by other workers (Will, 1967; Maclean and Wein, 1978). Comparing the available literature (Table X) on nutrient mass remaining after different periods of decomposition, P. kesiya was found to be highly efficient in nutrient release. This was also indicated by low residence time and high turnover rate of nutrients on the forest floor. TABLE X C o m p a r i s o n o f n u t r i e n t c h a n g e s d u r i n g d e c o m p o s i t i o n o f n e e d l e l i t t e r in t h e p r e s e n t s t u d y w i t h d a t a f r o m t h e l i t e r a t u r e . R e s u l t s a r e p r e s e n t e d as p e r c e n t a g e o f t h e o r i g i n a l n u t r i e n t m a s s r e m a i n i n g a f t e r various periods of decomposition Location

Tree species

Decomposition time (months)

Pinus s t r o b u s

12

Nutrient mass r e m a i n i n g (%) N

North Carolina (U.S.A.)

P

K

References

Ca

Mg

100 100 18 100 32

N e w B r u n s w i c k P. b a n k s i a n a (Canada)

12 24

85 148 22 83 133 18

47 43 31 37

P. b a n k s i a n a

12 24

103 188 17 102 185 17

80 63 50 68

P. k e s i y a

12 24

Shillong (India)

67 28

47 12 13 2

37 38 1 0 11

Cromack and Monk, 1975

Maclean and Wein, 1978

Present study

152

Thus under the climatic conditions prevailing at higher elevations in northeast India, Pinus kesiya is efficient, both in production and decomposition of litter as compared to other pine species of the world. These characteristics contribute towards a rapid turnover of nutrients. Forests of khasi pine often occur on soils of low fertility. The success of this species may therefore be dependent upon the turnover rate of nutrients. The frequency of flushing during the year, the shorter life span of the needles and the consequent high litter production along with faster release of nutrients may all contribute towards the success of P. kesiya as an early colonizer on comparatively infertile sites. ACKNOWLEDGEMENTS

This study was sponsored and supported b y the University Grants Commission, New Delhi, India. We thank D.I. Bevage, Forestry Department, Australia, for useful comments on this manuscript. The help rendered by the Forest Department, Meghalaya, India, is gratefully acknowledged.

REFERENCES Allen, S.E., Grimshaw, H.M., Parkinson, J.A. and Quarnby, C., 1974. Chemical Analysis of Ecological Materials. Blackwell Scientific Publications, Oxford, 565 pp. Alway, F.J. and Zon, R., 1930. Quantity and nutrient contents of pine leaf litter. J. For., 28: 715--727. Anderson, J.M., 1973. Stand structure and litter fall of a coppiced beech and sweet chestnut woodland. Oikos, 24 : 128--135. Bagnall, R.G., 1972. The dry weight and calorific value of litter fall in a New Zealand Nothofagu~ forest. N.Z.J. Bot., 10: 27--36. Bray, J.R. and Gotham, E., 1964. Litter production in forests of the world. Adv. Ecol. Res., 2: 101--157. Bremner, J.M., 1960. Determination of nitrogen in soil by the Kjeldahl method. J. Agric. Sci., 55: 11--33. Carlisle, A., Brown, A.H.F. and White, E.J., 1967. The nutrient contents of tree stem flow and ground flora litter and leachates in a sessile oak (Quercus petraea) woodland. J. Ecol., 54: 65--85. Coldwell, B.B. and DeLong, W.A., 1950. Studies of the composition of deciduous forest tree leaves before and after partial decomposition. Sci. Agric., 30: 456--466. Cole, D.W., Turner, J. and Gessel, S.P., 1975. Elemental cycling in Douglas-fir ecosystems of the Pacific Northwest: a comparative examination. Paper presented at 12th Int. Bot. Congr., Leningrad, U.S.S.R., 12 pp. (mimeogr.). Cromack, K. and Monk, C.D., 1975. Litter production, decomposition, and nutrient cycling in a mixed hardwood watershed and a white pine watershed. In: F.G.H. Howell, J.B. Gentry and M.H. Smith (Editors), Mineral Cycling in South Eastern Ecosystems. U.S. Energy Research and Development Administration, Springfield, VA, pp. 609--624. Ebermayer, E., 1976. Die gesamte Lehre der Waldstreu m i t Riicksicht auf die chemische ~tatik des Waldbaues. Springer, Berlin, 116 pp. Fogel, R. and Cromack, K., Jr., 1977. Effect of habitat and substrate quality on Douglasfir litter decomposition in western Oregon. Can. J. Bot., 55: 1632--1640. Foster, N.W., 1974. Annual macro element transfer from Pinus banksiana Lamb. forest to soil. Can. J. For. Res.. 4: 470--476.

153 Freezaillah, B.C.Y., 1966. Some notes on Pinus caribaea Mor. grown in Malaya. Paper presented at Pan-Malaysian Forestry Conference, 10--17 Sept. 1966, Forestry Department o f Malaya, Forest Research Institute Kualalumpur, No. 54, 8 pp. Gessel, S.P. and Turner, J., 1974. Litter production by red alder in western Washington. For. Sci., 20: 325--330. Hayes, A.J., 1965. Studies on the decomposition of coniferous leaf litter. I. Physical and chemical changes. J. Soil Sci., 16: 121--140. Howard, P.J.A. and Howard, D.M., 1974. Microbial decomposition of tree and shrub leaf litter. I. Weight loss and chemical changes of decomposing litter. Oikos, 25: 341--352. Johnson, N.M., Likens, G.E., Bormann, F.H. and Pierce, R.S., 1968. Rate of chemical weathering of silicate minerals in New Hampshire. Geochim. Cosmochim. Acta, 32: 531--545. Lamb, D. and Florence, R.G., 1975. Influence of soil type on the nitrogen and phosphorus content of radiata pine litter. N . Z . J . For. Sci., 5: 143--151. Lousier, J.D. and Parkinson, D., 1976. Litter decomposition in a cool temperate deciduous forest. Can. J. Bot., 54: 419--436. Lutz, H.J. and Chandler, R.F., 1946. Forest Soils. Wiley, New York, NY, 514 pp. Maclean, D.A. and Wein, R.W., 1978. Litter production and forest floor dynamics in pine and hardwood stands of New Brunswick, Canada. Holartic Ecol., 1: 1--15. Malkonen, E., 1974. Annual primary production and nutrient cycle in some Scots pine stands. Commun. Inst. For. Fenn., 84" 1--87. Mikola, P., 1960. Comparative experiments on decomposition rates of forest litter in Southern and Northern Finland. Oikos, 11: 161--166. Newbould, P.J., 1967. Methods for estimating the Primary Production of Forests. IBP Handbook no. 2. Blackwell Scientific Publications, Oxford. Olson, J.S., 1963. Energy storage and the balance of producers and decomposers in ecological systems. Ecology, 4 4 : 3 2 2 - - 3 3 1 . Ovington, J.D., 1962. Quantitative ecology and the woodland ecosystem concept. Adv. Ecol. Res., 1: 103--192. Peach, K. and Tracey, M.V. (Editors), 1956. Modern Methods of Plant Analysis, Vol. I. Springer, Berlin, 542 pp. Scott, D.R.M., 1955. A m o u n t and chemical composition of the organic matter contributed by overstorey and understorey vegetation to forest soil. Yale Univ. Sch. For. Bull. 62, 73 pp. Subba Rao, B.K., Dabral, B.G. and Pande, S.K., 1972. Litter production in forest plantation of chit (Pinus roxburghii), teak (Tectona grandis) and sal (Shorea robusta) at New Forest, Dehra Dun. In: P.M. Golley and F.B. Golley (Editors), Tropical Ecology with an Emphasis on Organic Productivity. International Society for Tropical Ecology, University of Georgia, Athens, GA, pp. 235--243. Tappeiner, J.C. and Aim, A.A., 1975. Undergrowth vegetation effects on the nutrient content of litter fall and soils in red pine and birch stands in northern Minnesota. Ecology, 56: 1193--1200. Thomas, W.A., 1968. Decomposition of loblolly pine needles with and without the addition of dogwood leaves. Ecology, 49: 568--571. Walter, H. and Haber, W., 1957. Uber die Intensit/it der Bodenatmung mit Bemerkungen zu den Lundergardschen Werten. Bar. Dtsch. Bot. Ges., 70: 257--282. Wells, C., Whigham, D. and Lieth, H., 1972. Investigation of mineral nutrient cycling in an upland Piedmont Forest. J. Elisha Mitchell Sci. Soc., 88: 66--78. Wiegert, R.G. and Monk, C.D., 1972. Litter production and energy accumulation in three plantations of longleaf pine (Pinus palustris Mill.). Ecology, 53: 949--953. Will, G.M., 1961. Decomposition of Pinus radiata litter on the forest floor. Part I. Changes in dry matter and nutrient content. No. 2. J. Sci., 10: 1030--1044. Witkamp, K., 1966. Rates of carbon dioxide evolution from the forest floor. Ecology, 47 : 492--494. Zavitkovski, J. and Newton, M., 1971. Litter fall and litter accumulation in red alder stands in Western Oregon. Plant Soil, 35: 257--268.