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Population dynamics and production studies of species of centropyxidae (Testacea, Rhizopoda) in an aspen woodland soil
Arch. Protistenk, 130 (1985):
165~178
Department of Biology, The University of Calgary, Calgary, Alberta, Canada
Population Dynamics and Production Studies of Species of Centropyxidae (Testacea, Rhizopoda) in an Aspen Woodland Soil By J. DANIEL LOUSIER With 3 Figures Key words: Population dynamics; production; ecology of soil; Centropyxidae; Rhizopoda
Summary Twelve species of Centropyxidae and 1 species of PJagiopyxidae were observed as live cells or empty tests throughout the study period in an aspen woodland soil. Only 3 centropyxid species were considered constant and comprised 4 % of the mean annual abundance, 19 % of the mean annual biomass, 2 % of the total production numbers and 10.5 % of the total secondary production for all species of Testacea. Including the total production biomass for C. sylvatica, an incidental species, the total centropyxid production for the year increased to 20 % of the total testacean production. For the Centropyxidae, mean annual biomass and total annual production were measured as 0.14 and 41.1 g wet weight· m- 2 respectively, while total annual ingestion, respiration losses and egestion losses were calculated as 274, 68.5 and 164.4 g' m- 2 respectively. The annual production biomass varied from 115 to 225 times (mean 160) the standing crop of Centropyxidae in all the soil layers. The dry weight of carbon respired annually by the centropyxids was estimated as 3.22 g : m- 2 , which amounted to 1.2 % of the total annual carbon input.
Introduction Little is known about several aspects of the ecology of soil Testacea, especially annual population dynamics, secondary production, biomass turnover and impact on the organic cycle. The Euglyphidae have received some interest (SMITH 1973; SCHONBORN 1975, 1977, 1978, 1982; COi1TEAUX 1976, 1978; LAMINGER 1978; LAMINGER et al. 1980) but other families, such as the Centropyxidae, have been the object of only limited study. Several other aspects, particularly taxonomy and geographical distribution (DEFLANDRE 1929; THOMAS 1958; BONNET and THOMAS 1960; DECLOITRE 1977, 1978, 1979a, b, 1982), are reasonably well known. Much basic biological information is still unavailable and the interpretation of much of the ecological information available is limited by this. NETZEL (1972, 1975, 1976) and HEDLEY et al. (1976) have provided important information on cellular ultrastructure and test morphology and formation in species of Centropyxis. Some ecological information, e.g., annual fluctuations in density and biomass, annual production, generation times, number of generations per year and mortality rates, is available in bits for a few species of Centropyxidae (LOUSIER 1974a, b; SCHONBORN 1977, 1978, 1982; COUTEAUX 1978; LAMINGlCR et al. 1980; FOISSNER and ADAM 1981). The objectives of this paper are to
166
.J. D. Lousrnn
detail (1) the annual variation in density, biomass, production and turnover in each of the soil and litter layers, (2) the relationship to the total testacean community, and (3) the relative importance in the aspen woodland soil of the Centropyxidae. The study was carried out in a cool temperate deciduous woodland for a period of 57 weeks.
The Study Area The general study area encompassed about 21 km 2 at the northern end of the Kananaskis Valley in the Fisher Range of the Rocky Mountains in Alberta, Canada. Detailed descriptions of the site, including additional information on the soil, vegetation, climate, litter input, litter decomposition, and litter and soil chemistry, were provided by LOUSIER (1974a, 1975, 1976) and LOUSIER and PARKINSON (1976, 1978, 1979). To briefly summarize then, the study site was an aspen woodland located at 1,400 m a.s.l. on a well-drained, south-facing slope. The climate is continental, characterized by short, dry summers and relatively long, cold winters with intermittent, warm, chinook winds. The soil has been classified in the orthic gray luvisol subgroup, and has a surface organic horizon easily separated into L- (whole litter), F - (fragmented litter), H- (humus) and Ah- (black mineral) layers (I.. OUSIER 1974a). The canopy was dominated by trembling aspen (POpUlU8 iremuloides MICHx.),with balsam poplar(P. bal8amifera L.) being less frequent in occurrence. Various grasses, herbs and wild rose shrubs are the main components of the understory.
Methods The arrangement of the study plots in the aspen woodland site has been illustrated in LOUSIER and PARKINSON (1979); the sample preparation techniques and sample examination procedures were outlined by LOUSIER and PARKINSON (1981 a); and the sampling program and population analysis equations were developed in LOUSIER (1984b).
Results Twelve species of Centropyxidae and 1 species of Plagiopyxidae were observed as live cells or empty tests throughout the study period in the aspen woodland soil (Table 1). Only 3 of these species could be considered constant in frequency (sensu COUTEAUX 1976) and were subjected to the detailed population analysis; the others were either incidental or accidental (Table 1). Table 1 also presents the biomass (wet weight· 10-6 cells) measured for each species of Centropyxidae and Plagiopyxidae recorded in the study. Estimates of the live weight of an individual cell were made by calculating the volume of the cell and assuming a specific gravity of about 1.0 (HEAL 1970). The estimates were made primarily on live individuals isolated from field samples with some augmentation with measurements from the COUTEAUX slides. There was no observed seasonal or spat al variation in cell size or biomass. The estimates given in Table 1 compare favourably with those given in ScnoNBoRN (1977). Only O. aerophila, O. aerophila var. 8phagnicola and O. eurqstoma were found living in all 4 soil layers, and were recorded in the decomposing leaf litter after 12, 18 and 36 months decomposition, respectively, generally increasing in biomass from the time of initial colonization (LOUSIER 1982). It should be anticipated that, because of the mineral or the sediment particles required for test construction, the Centropyxidae should be later colonizers and should increase in biomass with the age of the litter and with depth of organic layer profile.
0 .5
25 .1
12.8
1.1
20
20
10
10 80
10
0.7
20 20
±
±
± 0.4
±
± 0.6 25.1 ± 1.1 59. 1 ± 2.0 157.0 ± (;.4
9.4 Hi. 8
20
80 20
100
100
N o . of ce lls m easured F
+1+ + /+ + 1+ + /+ + /+ +/ + + /+ - /+ +1+ + /+ - /- + /+ - /- +1+ - /- - 1+ - /- +/+
2)+/ + +1+ + /+ - /+ - /+ - /+ - /+ - /-
L
Distribut ion
3) Co n s tancy : S pec ies o bser ve d in > 50 % of samples - c on s tan t. in frequency ; Species obser ved in 25-50 % of samples - inc id ental in frequenoy , S p e cies observed in < 25 % of samples - nc c id e n t.a l in frequency (CmiTEAux 1976).
2) O bserved a s liv in g /o b ser ve d as em p t y t ests
I) S tan d a r d error
O. p laoios toma B ONNE1' a n d THOMAS O. minuta D EFI,ANDHB G. platystoma (PEN,\R D) DEFLANDRE G. la evigata P ENAHD Gyc lop yxis eurpstoma DEFLANDHE G. eu ru stom a va l'. qauthieri an no BONNET and T HOMAS G. k ahli. D E}'LANDltE G. p uteus THOMAS Plag iopyx is call ida !'}lNAJlD
G. cassis (\VAI_LI CII) D EFLANDRE
6.1
12.4
O. •~ylva tica (DIWLANDRE) THOMAS
10.0
G. aeroph ila v u r . s p ha onicola DEFLANDRE
± O.liI ) ± 0.6 160 .0 ± 7.7 12.:1 ± 0. :> 25.1 ± 1.2
Bi oma ss
Gentrop y x is aero phila DEt'LANDHE
S p ecies o bs e rve d
--+1+ + /+ +/+ +1+ + /+ +/ + + /+ +/ + +1+ + /+ + 1+ + 1+ + /+
H
+ /+ + /+ - 1+ - /+ - /+ -/ + -/ + - 1+ +/ + +/ + + 1+ - /+ + /+
Ah
0
0
0
0
100
0
0
0
0
0
:14
100
100
L
10
0
26
10
100
0
12
12
:18
14
50
100 100
F
18
12
:14
18
100
8
20
20
46
28
44
100
100
H
Cons t.anoy ( %)3)
12
0
8
8
0 94
()
0 0
0
114 0
100
All
Tabl e l. O ccurrence, di stribution, biomass (mg· 10 - 6 cells) a n d co n s t a n cy of spec ies o f Ce n t r op y x id a e a n d Plagiopyxida e in the o rgan ic lay ers o f th e aspen woodland so il
0 '"
~
-:I
...-
g"
'< ~.
'"0
"::;.
('J
S,
'<
'0'0"
trj
s"::::
~
168
J. D.
800
LOUSa;R
Cenlropyxis oerophi/o
AOO
•
AOOO
F
• ~
i
.. . •
>-
"'0
til
Q.
< w U
< to-
I/)
•
6000
w
to-
.... 0
•
AOOO
Ill: W I:C
~
::> Z
2000
•
Fig. 1. The annual fluctuations of numbers of active, encysted and empty tests of Centroputci« aerophila (- - - encysted tests; • indicates significant difference from previous • for active or emtpy tests; • indicates significant difference from previous. for encysted tests).
Centropyxis aerophila The populations in the four soil layers all had peaks in active abundance in late November and late February (Fig. 1). The H- and Ah-layer populations also had peaks in late October (i.e., after leaf fall). During the rest of the study period, the populations were quite low and quite static. C. aerophila was the only species to have its highest number of generations per year in the Ah-layer (Table 2). In relation to the other species, C. aerophila had low intrinsic rates of natural increase, biomass turnover rates,
169
Population Ecology of Centropyxidae
2000
Csnfropyxis oerophi/o
•
1000
ol==:::::::::::====:::::::::::::::....-----=::::=...--....,..--==;:=----..!---l
•
4000
3000
2000
1000
• • 01---------------------------;------1
\I)
:;; w I-
>-
I-
8000
e,
~ w ...
o
6000
H
•
•
Ill: W
;
4000
::> Z
Fig. 1.
and number of generations per year in the L-, F- and H-layers, but higher than average Band P B for these layers. This species had its highest r in summer, fall and winter in the Lvlayer, all seasons in the F-, spring, summer and winter in the H-, and summer and winter in the Ah-layer. The P B followed the same trend in the L-layer but showed no trends for the other layers. PB/B peaked in the summer, fall and winter in the Llayer, spring, summer and fall in the F-layer, spring and summer in the H-layer and in all seasons in the Ah-layer. The fastest generation times recorded were: L - 1.3 d (late January), F - 1.2 d (mid-June, mid-July), H - 1.5 d (mid-August), and Ah1.8 d (mid-December). C. aerophila accounted for about 5 % of the total annual P B for all 28 species and almost 25 % of the total annual centropyxid production.
170
J. D.
LOUSIER
Table S. Summary of the population parameters calculated for Centropyxis aerophila.
:1"
L
Ah
H
Annual mean density (D) (X 106 • m- 2)
0.20
± 0.03 1)
1.32
± 0.23
4.05
± 0.65
0.46
± 0.07
Annual mean relative density (RD) (%) Annual mean biomass (B) (mg : m- 2 )
1.73
± 0.28
2.44
± 0.35
2.99
± 0.35
3.07
± 0.35
1.93
± 0.25
13.06
Annual mean relative biomass (RB) (%)
5.18
± 0.67
6.94
Production numbers (P N ) (X 106 • m- 2 • y-l)
22.4
Annual mean r (d-1 )
0.103
0.197
0.141
0.205
Annual mean generation time (T) (d)
8.9
5.8
6.5
4.0
Number of generations
50.4
± 2.36 ± 0.87
219.0
± 0.009 ± 0.9
± 0.017 ± 0.9
94.1
34.03
± 4.93
13.97
± 1.85
11.23
± 1.30
12.53
± 1.34
456.2
± 0.012 ± 0.5
66.6
317.5
± 0.012 ± 0.02
98.2
(G) (y-1)
± 0.2
Annual mean mortality rate (% . d-1)
7.3
Production biomass (Pn) (mg· m- 2 • y-l)
224.0
Annual mean Pn/B (week-I)
2.4
9.9
± 0.4
2,190.1
± 0.3
8.4
± 2.1
8.4
± 0.3
4,562.3 4.3
± 1.2
11.2
± 0.2
3,174.8 5.7
± 0.8
1) Standard error
Centropyxis aerophila var. sphagnicola The population fluctuations shown in Fig. 2 indicated little variation in pattern between the soil layers and compared favourably with those for C. aerophila, with the major peaks in late November and late February in all four layers. C. aerophila var. sphaqnicola was one of the lowest ranked species in terms of P N and G in the L-, Fand H-layers, and of rand PB/B in the F-, H- and Ali-layers (Table 3). It ranked near the middle of the range for Band P B and had the slowest T of all species in the Hlayer. The fastest generation times recorded were: L - 1.6 d (late February), F 1.4 d (mid-September), H - 1.4 d (late November), and Ah - 1.5 d (late November). The r peaked at the following times: L - fall, winter, F - all seasons, H - fall, winter and Ah - fall only. The P B had the same patterns in the L- and F-layers but in the Il-layer it peaked in all seasons and in the Ah-layer it had lower values only in summer. About 2.4 % of the annual total P B and 12 % of the total annual centropyxid P B were accounted for by C. aerophila var. sphagnicola. Cyclopyxis eurystoma There was a considerable similarity between the patterns of the fluctuations of the active population in each of the soil layers, with three seasons having concident, major peaks in abundance of C. eurystoma (summer, fall, winter; Fig. 3). There was an autunm peak during the initial stages of leaf fall in the L- and F-layers, and after leaf fall in the F-, H- and Ah-layers. The mid-August and late January peaks occurred simultaneously in all layers. Cysts were infrequent but, at times, exceeded the active forms in number.
171
Population Ecology of Centropyxidae
L
o~======:::::===:::::::::::==:::::===:i.~:::::::==:::::~:::::=-l F
1000
0 0(
w
H
1AOO
~
•
III
W I-
1000
....
o
Ql: W
600
all
•
~ Z
200
•
,.
' ....
0 200
• 0 MAR
C,nlropyxis tMrophi/a var. spllagnicoh
1000
i,. -u
0
•
Q
i
3000
III
I-
III
W I-
....>A.
1000 0 3000
~
W
•
....
0
•
Ql:
w
all
~ ::l
Z
SOO 0
• MAR
Fig. 2. The annual fluctuations in numbers of active, encysted and empty tests of Centropyxis aerophila var, sphagnicola (... encysted tests; • indicates significant difference from previous. for active or empty tests; • indicates significant difference from previous. for encysted tests).
172
J. D. Lo usr !(It
Table 3. Summary of the population parameters calculated for Centropyxis oerophila var. epluumicola F
L
H
Ah
Annual mean density (D) (X 10-6 • m- 2 )
0.10
±
O.OP)
0.66
±
0.07
1.16
±
0.14
0.27
±
Annual mean relative density (RD) (%) Annual mean biomass (B) (mg· m- 2 )
0.79
±
0.11
1.23
± 0.13
1.22
±
0.24
2.68
± 0.43
1.16
± 0.14
8.24
±
12.75
Annual mean relative biomass (RB) (%)
3.00
±
4.38
± 0.40
Production numbers (PN) (X 106 • m- 2 • y_l)
14.7
Annual mean r (d ")
0.146
0.134
0.118
0.126
Annual mean generation time ('1') (d) Number of generations (G) (y-I)
6.3
7.0
9.2
7.3
Annual mean mortality rate (% . d- I)
10.1
Production biomass (Pn) (mg : m- 2 • h- I)
182.0
Annual mean PB/B (week-I)
4.0
0.37
0.89
108.5
± 0.011 ± 0.7
± 0.1
± 0.5
9.8
± 0.013 ± 0.9
± 0.3
±
± 0.48
4.68
1.2
8.8
± 0.013 ± 0.9
±
±
±
1.05
11.20
±
1.13
±
0.011
±
0.6
60.2 0.3
1,773.4 3.1
10.73
139.7
57.1
1,345.6 5.8
1.33
143.0
82.7
69.5
±
0.03
0.7
9.2
±
0.3
1,731.8 3.5
±
0.6
1) Standard error
The r peaked in summer, fall and winter in the Lvlayer, in all seasons in the Flayer, and in summer and winter in the H- and Ah-layers, P B behaved in a similar fashion in the L- and F-Iayers but, in the H- and Ali-layers, showed no seasonal trends. PB/B peaked in all seasons in the L- and Ali-layers, in spring, summer and fall in the F-Iayer, and in winter, spring and summer in the H-Iayer. The fastest generation times observed were: L ~ 1.3 d (late January), F ~ 1.2 d (early June, mid-July), H ~ 1.5 d (mid-August) and Ah ~ 1.8 d (mid-December). C. eurystoma accounted for 3 % of the total annual secondary production and 16 % of the total annual centropyxid production. In comparison with the other 14 constant species, C. eurystoma was among the lowest ranked for T, G, r, P N and PB/B in the F-, H- and Ali-layers, but about the middle of the range for these parameters in the I.-layer (Table 4).
Discussion Several general, summary comments can be made with regard to the information shown in Figs. 1~3. The patterns for the populations fluctuations in the 4 organic layers were usually similar with all major peaks occurring at that same time in each layer. This differs somewhat from the eulyphid situation in which the Lsla.yer pattern was usually quite distinct (LOUSIER 1984a). This could possibly be explained by the apparent preference for the deeper organic layers by the Centropyxidae present. The 3 constant species each had a major peak in the autumn in each layer either just after leaf litter fall or just after the onset of the winter freeze. The Centropyxidae maintained
173
Population Ecology of Centropyxidae Cyc!opyX/S #ufysfoma
100
1>00
i ~
<00
-e
'" i
200
«
'"
...~ . woo ...'"'"
H
..'" (5
:E ::>
z
3500
i ~
'"
!
2500
1500
l!!
'" ...'"
500
~
...
:E
IlOOO
.
'000
'"
(;
:lj
:E
::> Z
2000
'000
Fig. 3. The annual fluctuations in numbers of active, encysted and empty tests of Oyclopyxis eurystoma (- - - encysted tests; • indicates significant difference from previous. for active or empty tests; • indicates significant difference from previous. for encysted tests).
174
J. D.
LOUSIER
Table 4. Summary of the population parameters calculated for Cyclopyxi8 eurustoma F
L
Ah
H
Annual mean density (D) (X 106 • m- 2 )
0.09
±
0.02 1)
0.53
±
0.05
1.32
± 0.16
0.38
±
Annual mean relative density (RD) (%)
0.79
±
0.21
1.15
±
0.13
1.24
±
3.47
± 0.41
Annual mean biomass (B) (mg· m- 2 )
1.02
± 0.21
6.89
±
0.74
15.75
Annual mean relative biomass (RB) (%)
2.66
±
4.85
±
0.75
5.50
Production numbers (P N ) (X 106 • m- 2 • y-I) Annual mean r (d-I)
15.4
91.7
0.148 ± 0.016 7.4 ± 0.8
0.171
Number of generations (G) (y-I)
71.0
81.7
Annual mean mortality rate (M) (% . d- I)
9.8
Production biomass (PB) (mg : m- 2 • y-I)
197.6
Annual mean PB/B (week- 2 )
4.6
Annual mean generation time (T) (d)
±
±
0.51
0.3
8.1
9.6
7.0
±
2.14
± 0.66
198.1
±
±
0.020
1.2
0.152 8.0
±
± 0.4
±
1.9
9.8
±
0.018
0.9
±
1.43
15.05
±
1.22
±
0.012
0.129 8.0
±
0.7
±
0.3
67.0
±
0.2
2,536.3 3.7
16.46
197.8
66.3
1,174.1 0.9
0.15
0.03
±
0.6
9.7
2,531.9 3.6
± 0.5
I) Standard error
substantial, active (reproducing) populations over the winter period. In fact, O. aerophila and O. aerophila var. sphaqnicola reached their maximum abundance in each layer for the year while the soil was frozen, and O. eurystoma had a major sustained peak near the end of January. The Centropyxidae did not increase in abundance during the later winter - early spring period as did the Euglyphidae (LOUSIER 1984a) and Difflugiella oviformis (LOUSIER 1984b). The patterns of the fluctuations in numbers of empty tests tended to closely parallel those for the active tests, perhaps indicating a rapid turnover of empty tests (LOUSIER and PARKINSON 1981b). The variations in cyst number, when the cysts were recorded, generally paralleled the fluctuations of active forms, i.e., coincident increases and decreases. Tables 2-4 show that for all the constant species, annual mean weekly density increased with profile depth to the H-layer. The same was so for annual mean weekly biomass except for O. eurystoma, whose biomass increased with depth to the Ah-layer. The highest annual production totals for numbers and biomass were highest in the H- and lowest in the L-layer. For O. eurystoma, production in the Ah- was as high as in the H-layer. The annual mean daily intrinsic rate of natural increase was highest in the F-layer for O. aerophila, in the Ah-layerfor O. aerophila, and in the L-layer for O. aerophila var. sphagnicola. The 3 constant species had their highest number of generations in the F-layer. The annual weekly mean PB/B was highest in the F-layer for all the species. The 3 constant centropyxid species represented 4 % of the mean annual density respectively and 19 % of the mean annual biomass (Table 5). LAMINGER (1978) found that the Centropyxidae comprised 12 % of the total living Testacea in an alpine brown-
175
Population Ecology of Centropyxidae
Table 5. Comparisons between the 3 constant species of Centropyxidae, the 14 constant species in the total community, and the 28 species comprising the total testacean community Totals for constant centropyxidae Mean annual density (D) (X 106 • m- 2 )
L Ii' H
17 62 157 20
18 64 158 21
Total
10.5
256
261
L Ii' H
4.1 28.2 62.5 41.2
36 148 276 119
46 210 346 121
Total
136.0
579
723
L Ii' H
53 419 797 655
5,034 19,850 37,052 25,056
5,190 20,677 38,197 26,862
Total
1,924
86,992
90,926
L F H Ah
604 4,710 8,872 7,439
8,295 48,158 91,428 30,504
14,479 59,950 100,995 31,107
21,624
178,385
206,531
Ah
Production number (P N ) (X 106 • m- 2 • y-l)
Ah
Production biomass (P B ) (mg. m- 2 • y-l)
Totals for all 28 species
2.5 6.5 1.1
Ah
Mean annual biomass (B) (mg· m- 2 )
Totals for the 14 constant species
Total
004
earths-podsol. In terms of total production numbers and total annual production, in the present study, the Centropyxidae comprised 2 % and 10.5 % respectively. With the exception of C. sylvatica, the remaining Centropyxidae were very intermittent in frequency and all together constituted considerably less than 1 % of the total annual production and were not included in the analysis. C. sylvatica with a constancy of 50 % or less, accounted for a mean of 49, 40 and 20 % of the biomass in the L-, Fand H-layers respectively when observed. The presence of C. sylvatica raised the total centropyxid secondary production for the year to: L - 4,315 mg . m -2 . y-l, F 14,284 mg' m-2 • v'. H - 15,059 mg' m- 2 • y-l, and total- 41,097 mg : m-2 • y-l, increasing the centropyxid portion of the total annual production to 20 %. In an ashmaple mull humus, SCHONBORN (1982) found that the Centropyxidae represented 21,57,14 and 57 % of the annual mean abundance, annual mean biomass, total annual production numbers and total annual production biomass respectively. In a beechwood mull-like moder, the centropyxids were found to comprise 16 and 43 % of the production numbers and production biomass, respectively (SCm)NBORN 1978). In moss cushions under beechwood, however this family made up only 14 % of the total annual production biomass (SCHONBORN 1977). The total annual production for Centropyxidae in the present study (21.6 g : m- 2) far exceeded the 0.02 g . m -2 • y-l, measured in the moss cushions under beechwood (SCHONBORN 1977), was 50 % greater than that (14.6 g' m- 2 • y-l) recorded in an ash-maple mull (SCHONBORN 1982), and was less than the 32.5 g . m- 2 • y-l estimated
17fi
J, D, Lousncu
Table 6. Energy budgets for the species of Centropyxidae in the aspen woodland soil (All estimates are wet weight of biomass, mg . m -2)
Mean annual biomass, B (X 10-3)
C. aerophila
C. aerophila var, sphagnicola
C. eurystorna
Ah
1.9 13.1 34.0 14.0
1.2 8.2 12.8 10.7
1.0 6.9 15.8 16.5
Total
63.0
32.9
40.2
L
F H
Total annual production, P
0.22 2.19 4.56 3.17
0.18 1.35 1.77 1.73
0.20 1.17 2.54 2.53
Total
10.14
5.03
6.44
L
Ah
1)0.38 3.65 7.60 5.28
Total
16.91 (5.08)
8.38 (2.53)
10.74 (3.23)
L
Ah
0.90 8.76 18.24 12.66
0.72 5.40 7.08 6.90
0.78 4.68 10.14 10.14
Total
40.56 (10.14)
20.10 (5.03)
25.74 (6.44)
L
Ah
1.5 (0.6) 14.6 (5.5) 30.4 (11.4) 21.1 (7.9)
1.2 9.0 U.8 11.5
1.3 7.8 16.9 16.9
Total
67.6 (25.4)
33.5 (12.6)
L
F H
Ah
Total annual respiration losses, R
F H
Total annual egestion losses, E
F H
Total annual ingestion, I
F H
(0.U)2) (1.10) (2.28) (1.59)
(0.22) (2.19) (4.56) (3.17)
0.30 2.25 2.95 2.88
(0.09) (0.68) (0.89) (0.87)
(0.18) (1.35) (1.77) (1.73)
(0.5) (3.4) (4.4) (4.3)
0.33 1.95 4.23 4.23
(0.10) (0.59) (1.27) (1.27)
(0.20) (1.17) (2.54) (2.53)
(0.5) (2.9) (6.4)
(6.3)
42.9 (16.1)
1) Values not in parenthesis represent 10 DC, where P = 0.15 I, R = 0.25 I and E = 0.60 I (ROGERSON 1981; LOUSIER and PARKINSON 1983).
2) Values in parenthesis represent optimum temperatures (15--25 DC), where P = 0.4 I, R = 0.25 I and E = 0.4 I (HEAL 1967; LAYBOURN 1976).
by SCH<)NBORN (1978) for a beechwood soil. C. aerophila in the moss had only 10generations per year and a lower mortality rate of 3.8 %(SCHONBORN 1977) when compared to the values for this species in the aspen woodland soil. C. aerophila var. sphagnicola on the other hand, had a higher mortality rate (12.5 %), shorter mean generation time (2.0 d), but substantially fewer generations per year (7) in the ash-maple mull (SCHONBORN 1982). C. eurystoma also appeared to have substantially greater biomass production in aspen study site. Starting with the estimates of secondary production, it is possible to approximate the amount of food consumed by the testacean populations (HEAL 1967; LAYBOURN 1976; see also Table fi). When the production total for C. sylvatica is included, the estimate for centropyxid consumption of bacteria is 274 g . m-2 • y-l, which amounts
Population Ecology of Centropyxidae
177
to 20 % of the total consumption of bacteria by all species of Testacea and 12 times the annual mean standing crop of bacteria (LOUSIER and PARKINSON 1984). The PB/B for the Centropyxidae ranged from 115 to 225, with a mean of 160 for all layers. The amount of carbon respired per year was estimated as: 6.85 g- m- 2 (dry weight) X 47 % (carbon content of amoebae, BAND 1959) = 3.22 g' m- 2. This amounted to 1.19% of the total annual carbon input to the soil for the Centropyxidae. The respiration losses for the Centropyxidae were slightly under 1/3those for the Euglyphidae (LouSIER and PARKINSON 1983), and represented 20 % of the total respiration losses of the entire testacean community, indicating an intermediate role for the Centropyxidae in the aspen woodland soil.
Acknowledgements Financial support for the study was provided by an NSERC Operating Grant (No. A2257) to Dr. DENNIS PARKINSON and an NRCC Postgraduate Scholarship to the author.
Literature BAND, R. N.: Nutritional and related biological studies on the free-living soil amoeba, Hartmannella rhysodes. J. Gen. Microbio!. 21 (1959): 80-95. BONNET, L., et THOMAS, R.: Fauna terrestre et d'eau douce des Pyrenees Orientales, 5. Theeamoebiens du sol. Paris 1960, 1-104. COUTEAUX, M.·M.: Dynamisme de I'equilibre des 'I'hecamoebiens dans quelques sols climaciques, Mem. Mus. Nat. Hist. Nat. N.S. ser, A. Zoo!' 96 (1976): 1-183. - Etude quantitative des Thecamoebiens edaphiques dans une savane a Loudetia a Lamto (Cote dIvoire]. Rev. Eco!. BioI. Sol 15 (1978): 401-412. DECLOITRE, L.: Le genre Cyclopyxis. Arch. Protistenk. 119 (1977): 31-53. - Le genre Centropyxis. I. Complements a jour au 31 decembre 1974 de la Monographie du genre parue en 1929. Arch. Protistenk. 120 (1978): 63-85. - Le genre Centropyxis II. Complements a jour au 31 decernbre 1974 de la Monographie du genre parue en 1929. Arch. Protistenk. 121 (1979a): 162-192. - Mises a jour au 31, 12, 1978 des mises it jour au 31, 12, 1974 concernant les genres Arcella, Centropyxis, Cyclopyxis, Euglypha et Nebela. Arch. Protistenk. 122 (1979b): 387-397. - Complements aux publications precedentcs mise a jour au 31. XII. 1981 des genres Arcella, Centropyxis, Cyclopyxis, Euglypha, N ebela et Trinema. Arch. Protistenk. 126 (1982): 393-407. DEFLANDRE, G.: Le genre Centropyxis Stein. Arch. Protistenk. 64 (1929): 322-375. FOISSNER, W., und ADAM, H.: Die Gemeinschaftsstruktur und Produktion der terricolen Testaceen (Protozoa, Rhizopoda) in einigen Boden der Osterreichischen Zentralalpen (Hohe Tauern, Glocknergebiet). Veroff, des Osterr. MaB.Hochgebirgsprogramms 4 (1981): 53-78. HEAL, O. W.: Quantitative studies on soil amoebae. pp. 120-126. In: O. GRAFF and J. E. SAT. CHELL (eds.): Progress in Soil Biology. Amsterdam 1967. - Methods of study of soil Protozoa. In: J. PHILLIPSON (ed.): Methods of study in soil ecology. Paris 1970, pp. 119-126. HEDLEY, R. H., OGnEN, C. G., and MORGAN, N. J.: Manganese in the shell of Centropyxis (Rhizopoda: Protozoa). Cel! Tiss. Res. 171 (1976): 543-549. LAMIl'GER, H.: The effect of soil moisture fluctuations on the Testacean species Trinema enchelys (EHRENBERG) LEIDY m a high mounta.n brown-carths-podsol and its feeding behaviour. Arch. Protistenk. 120 (1978): 446-454. - GEISLER-MoRODER, K., SIESS, A., SPISS, E., und SPISS, B.: Populationsdynamik terrestrischer Protozoen (Testacea, Rhizopoda) in zentralalpinen Lagen 'I'irols. I. Untersuchungen subalpiner Boden in Raum Obergurgl (TiroljOsterreich). Arch. Protistenk. 123 (1980): 280-323. LAYBOURN, J.: Energy budgets for Stentor coeruleus Ehrenberg (Ciliophora). Oecologia (Berlin{ West) 22 (1976): 431-437. 12 Arch. Protistenk. Bd. 130
178
.l . D. Lor-sn:n, Population Eoology of Ccntropyxidae
LOUSIER, J. D.: Effects of experimental soil moisture fluctuations on turnover rates of Testacea. Soil BioI. Biochem. 6 (1974a): 19-26. - Response of soil Testacea to soil moisture fluctuations. Soil Biol. Biochem. 6 (1974 b): 235-239 [Errata - Soil Biol. Biochem. 7 (1975): 185-188]. - Relationships between distribution of Testacea (Protozoa, Rhizopoda) and the soil habitat. Naturaliste can. 102 (1975): 57-72. - Testate amoebae (Rhizopoda, Testacea) in some Canadian Rocky Mountain soils. Arch. Protistenk. U8 (1976): 191-201. Colonization of decomposing deciduous leaf litter by Testacea (Protozoa, Rhizopoda): Species Succession, abundance and biomass. Oecologia (Berlin/West) 52 (1982): 381-388. Population dynamics and production studies of Euglyphidae (Testacea, Rhizopoda, Protozoa) in an aspen woodland soil. Pedobiologia 26 (1984a): 309-330. - Population dynamics and production studies of Phryganella acropodia and Difflugiella ovi[ormis (Testacea, Rhizopoda, Protozoa) in an aspen woodland soil. Pedobiologia 26 (1984b): 331-347. and PARKINSON, D.: Litter decomposition in a cool temperature deciduous forest. Can. J. Bot. 54 (1976): 419-436. - Chemical element dynamics in decomposing leaflitter. Can. J. Bot. 56 (1978): 2795-2812. - Organic matter and chemical element dynamics in an aspen woodland soil. Can. J. For. Res. 9 (1979): 449-463. - - Evaluation of a membrane filter technique to count soil and litter Testacea. Soil BioI. Biochem. 13 (198Ia): 209-215. - - The disappearance of empty tests of litter and soil testate amoebae (Testacea, Rhizopoda, Protozoa). Arch. Prot.istenk. 124 (1981 b): 312-336. - - Annual population dynamics and production ecology of Testacea (Protozoa, Rhizopoda) in an aspen woodland soil. Soil Biol, Biochem. (1984). NETZEL, H.: Die Bildung der Gehausewand bei der Thekamobe Centropyxis discoides (Rhizopoda, Testacea). Z. Zellforsch. 135 (1972): 45-54. - Morphologie und Ultrastruktur von Centropyxis discoides (Rhizopoda, Testacea). Arch. Protistenk. U7 (1975): 369-392. - Die Abscheidung der Gehausewand bei Centropyxis discoides (Rhizopoda, Testacea). Arch. Protistenk. U8 (1976): 53-91. ROGERSON, A.: The ecological energetics of Amoebae proteus (Protozoa). Hydrobiologica 85, 117-128. SCHONBORN, 'V.: Ermittlung der Jahresproduktion von Boden-Protozocn. I. Euglyphidae (Rhizopoda, Testacea). Pedobiologia 15 (1975): 415-424. Production studies on Protozoa. Oecologia (Berlin/West) 27 (1977): 171-184. Untersuchungen zur Produktion der Boden-Testeceen. Pedobiologia 18 (1978): 373-377. Estimation of annual production of Testacea (Protozoa) in mull and moder (II). Pedobiologia 23 (1982): 383-:393. SMITH, H. G.: The Signy Island Terrestrial reference sites: III. Population ecology of Corythion dubium (Rhizopoda: Testacida) in Site 1. Brit. Antarct. Surv, Bull., Nos. 33/34 (1973): 123-135. THOMAS, R.: Le genre Plagiopyxis Penard, Hydrobiologia 10 (1958): 198-224. Author's address: Dr. J. DANIE.L LOUSIER, Ecology Program, Research Branch, Ministry of Forests, 1450 Government St., Victoria, British Columbia, Canada V8W 3E7.
165~178
Department of Biology, The University of Calgary, Calgary, Alberta, Canada
Population Dynamics and Production Studies of Species of Centropyxidae (Testacea, Rhizopoda) in an Aspen Woodland Soil By J. DANIEL LOUSIER With 3 Figures Key words: Population dynamics; production; ecology of soil; Centropyxidae; Rhizopoda
Summary Twelve species of Centropyxidae and 1 species of PJagiopyxidae were observed as live cells or empty tests throughout the study period in an aspen woodland soil. Only 3 centropyxid species were considered constant and comprised 4 % of the mean annual abundance, 19 % of the mean annual biomass, 2 % of the total production numbers and 10.5 % of the total secondary production for all species of Testacea. Including the total production biomass for C. sylvatica, an incidental species, the total centropyxid production for the year increased to 20 % of the total testacean production. For the Centropyxidae, mean annual biomass and total annual production were measured as 0.14 and 41.1 g wet weight· m- 2 respectively, while total annual ingestion, respiration losses and egestion losses were calculated as 274, 68.5 and 164.4 g' m- 2 respectively. The annual production biomass varied from 115 to 225 times (mean 160) the standing crop of Centropyxidae in all the soil layers. The dry weight of carbon respired annually by the centropyxids was estimated as 3.22 g : m- 2 , which amounted to 1.2 % of the total annual carbon input.
Introduction Little is known about several aspects of the ecology of soil Testacea, especially annual population dynamics, secondary production, biomass turnover and impact on the organic cycle. The Euglyphidae have received some interest (SMITH 1973; SCHONBORN 1975, 1977, 1978, 1982; COi1TEAUX 1976, 1978; LAMINGER 1978; LAMINGER et al. 1980) but other families, such as the Centropyxidae, have been the object of only limited study. Several other aspects, particularly taxonomy and geographical distribution (DEFLANDRE 1929; THOMAS 1958; BONNET and THOMAS 1960; DECLOITRE 1977, 1978, 1979a, b, 1982), are reasonably well known. Much basic biological information is still unavailable and the interpretation of much of the ecological information available is limited by this. NETZEL (1972, 1975, 1976) and HEDLEY et al. (1976) have provided important information on cellular ultrastructure and test morphology and formation in species of Centropyxis. Some ecological information, e.g., annual fluctuations in density and biomass, annual production, generation times, number of generations per year and mortality rates, is available in bits for a few species of Centropyxidae (LOUSIER 1974a, b; SCHONBORN 1977, 1978, 1982; COUTEAUX 1978; LAMINGlCR et al. 1980; FOISSNER and ADAM 1981). The objectives of this paper are to
166
.J. D. Lousrnn
detail (1) the annual variation in density, biomass, production and turnover in each of the soil and litter layers, (2) the relationship to the total testacean community, and (3) the relative importance in the aspen woodland soil of the Centropyxidae. The study was carried out in a cool temperate deciduous woodland for a period of 57 weeks.
The Study Area The general study area encompassed about 21 km 2 at the northern end of the Kananaskis Valley in the Fisher Range of the Rocky Mountains in Alberta, Canada. Detailed descriptions of the site, including additional information on the soil, vegetation, climate, litter input, litter decomposition, and litter and soil chemistry, were provided by LOUSIER (1974a, 1975, 1976) and LOUSIER and PARKINSON (1976, 1978, 1979). To briefly summarize then, the study site was an aspen woodland located at 1,400 m a.s.l. on a well-drained, south-facing slope. The climate is continental, characterized by short, dry summers and relatively long, cold winters with intermittent, warm, chinook winds. The soil has been classified in the orthic gray luvisol subgroup, and has a surface organic horizon easily separated into L- (whole litter), F - (fragmented litter), H- (humus) and Ah- (black mineral) layers (I.. OUSIER 1974a). The canopy was dominated by trembling aspen (POpUlU8 iremuloides MICHx.),with balsam poplar(P. bal8amifera L.) being less frequent in occurrence. Various grasses, herbs and wild rose shrubs are the main components of the understory.
Methods The arrangement of the study plots in the aspen woodland site has been illustrated in LOUSIER and PARKINSON (1979); the sample preparation techniques and sample examination procedures were outlined by LOUSIER and PARKINSON (1981 a); and the sampling program and population analysis equations were developed in LOUSIER (1984b).
Results Twelve species of Centropyxidae and 1 species of Plagiopyxidae were observed as live cells or empty tests throughout the study period in the aspen woodland soil (Table 1). Only 3 of these species could be considered constant in frequency (sensu COUTEAUX 1976) and were subjected to the detailed population analysis; the others were either incidental or accidental (Table 1). Table 1 also presents the biomass (wet weight· 10-6 cells) measured for each species of Centropyxidae and Plagiopyxidae recorded in the study. Estimates of the live weight of an individual cell were made by calculating the volume of the cell and assuming a specific gravity of about 1.0 (HEAL 1970). The estimates were made primarily on live individuals isolated from field samples with some augmentation with measurements from the COUTEAUX slides. There was no observed seasonal or spat al variation in cell size or biomass. The estimates given in Table 1 compare favourably with those given in ScnoNBoRN (1977). Only O. aerophila, O. aerophila var. 8phagnicola and O. eurqstoma were found living in all 4 soil layers, and were recorded in the decomposing leaf litter after 12, 18 and 36 months decomposition, respectively, generally increasing in biomass from the time of initial colonization (LOUSIER 1982). It should be anticipated that, because of the mineral or the sediment particles required for test construction, the Centropyxidae should be later colonizers and should increase in biomass with the age of the litter and with depth of organic layer profile.
0 .5
25 .1
12.8
1.1
20
20
10
10 80
10
0.7
20 20
±
±
± 0.4
±
± 0.6 25.1 ± 1.1 59. 1 ± 2.0 157.0 ± (;.4
9.4 Hi. 8
20
80 20
100
100
N o . of ce lls m easured F
+1+ + /+ + 1+ + /+ + /+ +/ + + /+ - /+ +1+ + /+ - /- + /+ - /- +1+ - /- - 1+ - /- +/+
2)+/ + +1+ + /+ - /+ - /+ - /+ - /+ - /-
L
Distribut ion
3) Co n s tancy : S pec ies o bser ve d in > 50 % of samples - c on s tan t. in frequency ; Species obser ved in 25-50 % of samples - inc id ental in frequenoy , S p e cies observed in < 25 % of samples - nc c id e n t.a l in frequency (CmiTEAux 1976).
2) O bserved a s liv in g /o b ser ve d as em p t y t ests
I) S tan d a r d error
O. p laoios toma B ONNE1' a n d THOMAS O. minuta D EFI,ANDHB G. platystoma (PEN,\R D) DEFLANDRE G. la evigata P ENAHD Gyc lop yxis eurpstoma DEFLANDHE G. eu ru stom a va l'. qauthieri an no BONNET and T HOMAS G. k ahli. D E}'LANDltE G. p uteus THOMAS Plag iopyx is call ida !'}lNAJlD
G. cassis (\VAI_LI CII) D EFLANDRE
6.1
12.4
O. •~ylva tica (DIWLANDRE) THOMAS
10.0
G. aeroph ila v u r . s p ha onicola DEFLANDRE
± O.liI ) ± 0.6 160 .0 ± 7.7 12.:1 ± 0. :> 25.1 ± 1.2
Bi oma ss
Gentrop y x is aero phila DEt'LANDHE
S p ecies o bs e rve d
--+1+ + /+ +/+ +1+ + /+ +/ + + /+ +/ + +1+ + /+ + 1+ + 1+ + /+
H
+ /+ + /+ - 1+ - /+ - /+ -/ + -/ + - 1+ +/ + +/ + + 1+ - /+ + /+
Ah
0
0
0
0
100
0
0
0
0
0
:14
100
100
L
10
0
26
10
100
0
12
12
:18
14
50
100 100
F
18
12
:14
18
100
8
20
20
46
28
44
100
100
H
Cons t.anoy ( %)3)
12
0
8
8
0 94
()
0 0
0
114 0
100
All
Tabl e l. O ccurrence, di stribution, biomass (mg· 10 - 6 cells) a n d co n s t a n cy of spec ies o f Ce n t r op y x id a e a n d Plagiopyxida e in the o rgan ic lay ers o f th e aspen woodland so il
0 '"
~
-:I
...-
g"
'< ~.
'"0
"::;.
('J
S,
'<
'0'0"
trj
s"::::
~
168
J. D.
800
LOUSa;R
Cenlropyxis oerophi/o
AOO
•
AOOO
F
• ~
i
.. . •
>-
"'0
til
Q.
< w U
< to-
I/)
•
6000
w
to-
.... 0
•
AOOO
Ill: W I:C
~
::> Z
2000
•
Fig. 1. The annual fluctuations of numbers of active, encysted and empty tests of Centroputci« aerophila (- - - encysted tests; • indicates significant difference from previous • for active or emtpy tests; • indicates significant difference from previous. for encysted tests).
Centropyxis aerophila The populations in the four soil layers all had peaks in active abundance in late November and late February (Fig. 1). The H- and Ah-layer populations also had peaks in late October (i.e., after leaf fall). During the rest of the study period, the populations were quite low and quite static. C. aerophila was the only species to have its highest number of generations per year in the Ah-layer (Table 2). In relation to the other species, C. aerophila had low intrinsic rates of natural increase, biomass turnover rates,
169
Population Ecology of Centropyxidae
2000
Csnfropyxis oerophi/o
•
1000
ol==:::::::::::====:::::::::::::::....-----=::::=...--....,..--==;:=----..!---l
•
4000
3000
2000
1000
• • 01---------------------------;------1
\I)
:;; w I-
>-
I-
8000
e,
~ w ...
o
6000
H
•
•
Ill: W
;
4000
::> Z
Fig. 1.
and number of generations per year in the L-, F- and H-layers, but higher than average Band P B for these layers. This species had its highest r in summer, fall and winter in the Lvlayer, all seasons in the F-, spring, summer and winter in the H-, and summer and winter in the Ah-layer. The P B followed the same trend in the L-layer but showed no trends for the other layers. PB/B peaked in the summer, fall and winter in the Llayer, spring, summer and fall in the F-layer, spring and summer in the H-layer and in all seasons in the Ah-layer. The fastest generation times recorded were: L - 1.3 d (late January), F - 1.2 d (mid-June, mid-July), H - 1.5 d (mid-August), and Ah1.8 d (mid-December). C. aerophila accounted for about 5 % of the total annual P B for all 28 species and almost 25 % of the total annual centropyxid production.
170
J. D.
LOUSIER
Table S. Summary of the population parameters calculated for Centropyxis aerophila.
:1"
L
Ah
H
Annual mean density (D) (X 106 • m- 2)
0.20
± 0.03 1)
1.32
± 0.23
4.05
± 0.65
0.46
± 0.07
Annual mean relative density (RD) (%) Annual mean biomass (B) (mg : m- 2 )
1.73
± 0.28
2.44
± 0.35
2.99
± 0.35
3.07
± 0.35
1.93
± 0.25
13.06
Annual mean relative biomass (RB) (%)
5.18
± 0.67
6.94
Production numbers (P N ) (X 106 • m- 2 • y-l)
22.4
Annual mean r (d-1 )
0.103
0.197
0.141
0.205
Annual mean generation time (T) (d)
8.9
5.8
6.5
4.0
Number of generations
50.4
± 2.36 ± 0.87
219.0
± 0.009 ± 0.9
± 0.017 ± 0.9
94.1
34.03
± 4.93
13.97
± 1.85
11.23
± 1.30
12.53
± 1.34
456.2
± 0.012 ± 0.5
66.6
317.5
± 0.012 ± 0.02
98.2
(G) (y-1)
± 0.2
Annual mean mortality rate (% . d-1)
7.3
Production biomass (Pn) (mg· m- 2 • y-l)
224.0
Annual mean Pn/B (week-I)
2.4
9.9
± 0.4
2,190.1
± 0.3
8.4
± 2.1
8.4
± 0.3
4,562.3 4.3
± 1.2
11.2
± 0.2
3,174.8 5.7
± 0.8
1) Standard error
Centropyxis aerophila var. sphagnicola The population fluctuations shown in Fig. 2 indicated little variation in pattern between the soil layers and compared favourably with those for C. aerophila, with the major peaks in late November and late February in all four layers. C. aerophila var. sphaqnicola was one of the lowest ranked species in terms of P N and G in the L-, Fand H-layers, and of rand PB/B in the F-, H- and Ali-layers (Table 3). It ranked near the middle of the range for Band P B and had the slowest T of all species in the Hlayer. The fastest generation times recorded were: L - 1.6 d (late February), F 1.4 d (mid-September), H - 1.4 d (late November), and Ah - 1.5 d (late November). The r peaked at the following times: L - fall, winter, F - all seasons, H - fall, winter and Ah - fall only. The P B had the same patterns in the L- and F-layers but in the Il-layer it peaked in all seasons and in the Ah-layer it had lower values only in summer. About 2.4 % of the annual total P B and 12 % of the total annual centropyxid P B were accounted for by C. aerophila var. sphagnicola. Cyclopyxis eurystoma There was a considerable similarity between the patterns of the fluctuations of the active population in each of the soil layers, with three seasons having concident, major peaks in abundance of C. eurystoma (summer, fall, winter; Fig. 3). There was an autunm peak during the initial stages of leaf fall in the L- and F-layers, and after leaf fall in the F-, H- and Ah-layers. The mid-August and late January peaks occurred simultaneously in all layers. Cysts were infrequent but, at times, exceeded the active forms in number.
171
Population Ecology of Centropyxidae
L
o~======:::::===:::::::::::==:::::===:i.~:::::::==:::::~:::::=-l F
1000
0 0(
w
H
1AOO
~
•
III
W I-
1000
....
o
Ql: W
600
all
•
~ Z
200
•
,.
' ....
0 200
• 0 MAR
C,nlropyxis tMrophi/a var. spllagnicoh
1000
i,. -u
0
•
Q
i
3000
III
I-
III
W I-
....>A.
1000 0 3000
~
W
•
....
0
•
Ql:
w
all
~ ::l
Z
SOO 0
• MAR
Fig. 2. The annual fluctuations in numbers of active, encysted and empty tests of Centropyxis aerophila var, sphagnicola (... encysted tests; • indicates significant difference from previous. for active or empty tests; • indicates significant difference from previous. for encysted tests).
172
J. D. Lo usr !(It
Table 3. Summary of the population parameters calculated for Centropyxis oerophila var. epluumicola F
L
H
Ah
Annual mean density (D) (X 10-6 • m- 2 )
0.10
±
O.OP)
0.66
±
0.07
1.16
±
0.14
0.27
±
Annual mean relative density (RD) (%) Annual mean biomass (B) (mg· m- 2 )
0.79
±
0.11
1.23
± 0.13
1.22
±
0.24
2.68
± 0.43
1.16
± 0.14
8.24
±
12.75
Annual mean relative biomass (RB) (%)
3.00
±
4.38
± 0.40
Production numbers (PN) (X 106 • m- 2 • y_l)
14.7
Annual mean r (d ")
0.146
0.134
0.118
0.126
Annual mean generation time ('1') (d) Number of generations (G) (y-I)
6.3
7.0
9.2
7.3
Annual mean mortality rate (% . d- I)
10.1
Production biomass (Pn) (mg : m- 2 • h- I)
182.0
Annual mean PB/B (week-I)
4.0
0.37
0.89
108.5
± 0.011 ± 0.7
± 0.1
± 0.5
9.8
± 0.013 ± 0.9
± 0.3
±
± 0.48
4.68
1.2
8.8
± 0.013 ± 0.9
±
±
±
1.05
11.20
±
1.13
±
0.011
±
0.6
60.2 0.3
1,773.4 3.1
10.73
139.7
57.1
1,345.6 5.8
1.33
143.0
82.7
69.5
±
0.03
0.7
9.2
±
0.3
1,731.8 3.5
±
0.6
1) Standard error
The r peaked in summer, fall and winter in the Lvlayer, in all seasons in the Flayer, and in summer and winter in the H- and Ah-layers, P B behaved in a similar fashion in the L- and F-Iayers but, in the H- and Ali-layers, showed no seasonal trends. PB/B peaked in all seasons in the L- and Ali-layers, in spring, summer and fall in the F-Iayer, and in winter, spring and summer in the H-Iayer. The fastest generation times observed were: L ~ 1.3 d (late January), F ~ 1.2 d (early June, mid-July), H ~ 1.5 d (mid-August) and Ah ~ 1.8 d (mid-December). C. eurystoma accounted for 3 % of the total annual secondary production and 16 % of the total annual centropyxid production. In comparison with the other 14 constant species, C. eurystoma was among the lowest ranked for T, G, r, P N and PB/B in the F-, H- and Ali-layers, but about the middle of the range for these parameters in the I.-layer (Table 4).
Discussion Several general, summary comments can be made with regard to the information shown in Figs. 1~3. The patterns for the populations fluctuations in the 4 organic layers were usually similar with all major peaks occurring at that same time in each layer. This differs somewhat from the eulyphid situation in which the Lsla.yer pattern was usually quite distinct (LOUSIER 1984a). This could possibly be explained by the apparent preference for the deeper organic layers by the Centropyxidae present. The 3 constant species each had a major peak in the autumn in each layer either just after leaf litter fall or just after the onset of the winter freeze. The Centropyxidae maintained
173
Population Ecology of Centropyxidae Cyc!opyX/S #ufysfoma
100
1>00
i ~
<00
-e
'" i
200
«
'"
...~ . woo ...'"'"
H
..'" (5
:E ::>
z
3500
i ~
'"
!
2500
1500
l!!
'" ...'"
500
~
...
:E
IlOOO
.
'000
'"
(;
:lj
:E
::> Z
2000
'000
Fig. 3. The annual fluctuations in numbers of active, encysted and empty tests of Oyclopyxis eurystoma (- - - encysted tests; • indicates significant difference from previous. for active or empty tests; • indicates significant difference from previous. for encysted tests).
174
J. D.
LOUSIER
Table 4. Summary of the population parameters calculated for Cyclopyxi8 eurustoma F
L
Ah
H
Annual mean density (D) (X 106 • m- 2 )
0.09
±
0.02 1)
0.53
±
0.05
1.32
± 0.16
0.38
±
Annual mean relative density (RD) (%)
0.79
±
0.21
1.15
±
0.13
1.24
±
3.47
± 0.41
Annual mean biomass (B) (mg· m- 2 )
1.02
± 0.21
6.89
±
0.74
15.75
Annual mean relative biomass (RB) (%)
2.66
±
4.85
±
0.75
5.50
Production numbers (P N ) (X 106 • m- 2 • y-I) Annual mean r (d-I)
15.4
91.7
0.148 ± 0.016 7.4 ± 0.8
0.171
Number of generations (G) (y-I)
71.0
81.7
Annual mean mortality rate (M) (% . d- I)
9.8
Production biomass (PB) (mg : m- 2 • y-I)
197.6
Annual mean PB/B (week- 2 )
4.6
Annual mean generation time (T) (d)
±
±
0.51
0.3
8.1
9.6
7.0
±
2.14
± 0.66
198.1
±
±
0.020
1.2
0.152 8.0
±
± 0.4
±
1.9
9.8
±
0.018
0.9
±
1.43
15.05
±
1.22
±
0.012
0.129 8.0
±
0.7
±
0.3
67.0
±
0.2
2,536.3 3.7
16.46
197.8
66.3
1,174.1 0.9
0.15
0.03
±
0.6
9.7
2,531.9 3.6
± 0.5
I) Standard error
substantial, active (reproducing) populations over the winter period. In fact, O. aerophila and O. aerophila var. sphaqnicola reached their maximum abundance in each layer for the year while the soil was frozen, and O. eurystoma had a major sustained peak near the end of January. The Centropyxidae did not increase in abundance during the later winter - early spring period as did the Euglyphidae (LOUSIER 1984a) and Difflugiella oviformis (LOUSIER 1984b). The patterns of the fluctuations in numbers of empty tests tended to closely parallel those for the active tests, perhaps indicating a rapid turnover of empty tests (LOUSIER and PARKINSON 1981b). The variations in cyst number, when the cysts were recorded, generally paralleled the fluctuations of active forms, i.e., coincident increases and decreases. Tables 2-4 show that for all the constant species, annual mean weekly density increased with profile depth to the H-layer. The same was so for annual mean weekly biomass except for O. eurystoma, whose biomass increased with depth to the Ah-layer. The highest annual production totals for numbers and biomass were highest in the H- and lowest in the L-layer. For O. eurystoma, production in the Ah- was as high as in the H-layer. The annual mean daily intrinsic rate of natural increase was highest in the F-layer for O. aerophila, in the Ah-layerfor O. aerophila, and in the L-layer for O. aerophila var. sphagnicola. The 3 constant species had their highest number of generations in the F-layer. The annual weekly mean PB/B was highest in the F-layer for all the species. The 3 constant centropyxid species represented 4 % of the mean annual density respectively and 19 % of the mean annual biomass (Table 5). LAMINGER (1978) found that the Centropyxidae comprised 12 % of the total living Testacea in an alpine brown-
175
Population Ecology of Centropyxidae
Table 5. Comparisons between the 3 constant species of Centropyxidae, the 14 constant species in the total community, and the 28 species comprising the total testacean community Totals for constant centropyxidae Mean annual density (D) (X 106 • m- 2 )
L Ii' H
17 62 157 20
18 64 158 21
Total
10.5
256
261
L Ii' H
4.1 28.2 62.5 41.2
36 148 276 119
46 210 346 121
Total
136.0
579
723
L Ii' H
53 419 797 655
5,034 19,850 37,052 25,056
5,190 20,677 38,197 26,862
Total
1,924
86,992
90,926
L F H Ah
604 4,710 8,872 7,439
8,295 48,158 91,428 30,504
14,479 59,950 100,995 31,107
21,624
178,385
206,531
Ah
Production number (P N ) (X 106 • m- 2 • y-l)
Ah
Production biomass (P B ) (mg. m- 2 • y-l)
Totals for all 28 species
2.5 6.5 1.1
Ah
Mean annual biomass (B) (mg· m- 2 )
Totals for the 14 constant species
Total
004
earths-podsol. In terms of total production numbers and total annual production, in the present study, the Centropyxidae comprised 2 % and 10.5 % respectively. With the exception of C. sylvatica, the remaining Centropyxidae were very intermittent in frequency and all together constituted considerably less than 1 % of the total annual production and were not included in the analysis. C. sylvatica with a constancy of 50 % or less, accounted for a mean of 49, 40 and 20 % of the biomass in the L-, Fand H-layers respectively when observed. The presence of C. sylvatica raised the total centropyxid secondary production for the year to: L - 4,315 mg . m -2 . y-l, F 14,284 mg' m-2 • v'. H - 15,059 mg' m- 2 • y-l, and total- 41,097 mg : m-2 • y-l, increasing the centropyxid portion of the total annual production to 20 %. In an ashmaple mull humus, SCHONBORN (1982) found that the Centropyxidae represented 21,57,14 and 57 % of the annual mean abundance, annual mean biomass, total annual production numbers and total annual production biomass respectively. In a beechwood mull-like moder, the centropyxids were found to comprise 16 and 43 % of the production numbers and production biomass, respectively (SCm)NBORN 1978). In moss cushions under beechwood, however this family made up only 14 % of the total annual production biomass (SCHONBORN 1977). The total annual production for Centropyxidae in the present study (21.6 g : m- 2) far exceeded the 0.02 g . m -2 • y-l, measured in the moss cushions under beechwood (SCHONBORN 1977), was 50 % greater than that (14.6 g' m- 2 • y-l) recorded in an ash-maple mull (SCHONBORN 1982), and was less than the 32.5 g . m- 2 • y-l estimated
17fi
J, D, Lousncu
Table 6. Energy budgets for the species of Centropyxidae in the aspen woodland soil (All estimates are wet weight of biomass, mg . m -2)
Mean annual biomass, B (X 10-3)
C. aerophila
C. aerophila var, sphagnicola
C. eurystorna
Ah
1.9 13.1 34.0 14.0
1.2 8.2 12.8 10.7
1.0 6.9 15.8 16.5
Total
63.0
32.9
40.2
L
F H
Total annual production, P
0.22 2.19 4.56 3.17
0.18 1.35 1.77 1.73
0.20 1.17 2.54 2.53
Total
10.14
5.03
6.44
L
Ah
1)0.38 3.65 7.60 5.28
Total
16.91 (5.08)
8.38 (2.53)
10.74 (3.23)
L
Ah
0.90 8.76 18.24 12.66
0.72 5.40 7.08 6.90
0.78 4.68 10.14 10.14
Total
40.56 (10.14)
20.10 (5.03)
25.74 (6.44)
L
Ah
1.5 (0.6) 14.6 (5.5) 30.4 (11.4) 21.1 (7.9)
1.2 9.0 U.8 11.5
1.3 7.8 16.9 16.9
Total
67.6 (25.4)
33.5 (12.6)
L
F H
Ah
Total annual respiration losses, R
F H
Total annual egestion losses, E
F H
Total annual ingestion, I
F H
(0.U)2) (1.10) (2.28) (1.59)
(0.22) (2.19) (4.56) (3.17)
0.30 2.25 2.95 2.88
(0.09) (0.68) (0.89) (0.87)
(0.18) (1.35) (1.77) (1.73)
(0.5) (3.4) (4.4) (4.3)
0.33 1.95 4.23 4.23
(0.10) (0.59) (1.27) (1.27)
(0.20) (1.17) (2.54) (2.53)
(0.5) (2.9) (6.4)
(6.3)
42.9 (16.1)
1) Values not in parenthesis represent 10 DC, where P = 0.15 I, R = 0.25 I and E = 0.60 I (ROGERSON 1981; LOUSIER and PARKINSON 1983).
2) Values in parenthesis represent optimum temperatures (15--25 DC), where P = 0.4 I, R = 0.25 I and E = 0.4 I (HEAL 1967; LAYBOURN 1976).
by SCH<)NBORN (1978) for a beechwood soil. C. aerophila in the moss had only 10generations per year and a lower mortality rate of 3.8 %(SCHONBORN 1977) when compared to the values for this species in the aspen woodland soil. C. aerophila var. sphagnicola on the other hand, had a higher mortality rate (12.5 %), shorter mean generation time (2.0 d), but substantially fewer generations per year (7) in the ash-maple mull (SCHONBORN 1982). C. eurystoma also appeared to have substantially greater biomass production in aspen study site. Starting with the estimates of secondary production, it is possible to approximate the amount of food consumed by the testacean populations (HEAL 1967; LAYBOURN 1976; see also Table fi). When the production total for C. sylvatica is included, the estimate for centropyxid consumption of bacteria is 274 g . m-2 • y-l, which amounts
Population Ecology of Centropyxidae
177
to 20 % of the total consumption of bacteria by all species of Testacea and 12 times the annual mean standing crop of bacteria (LOUSIER and PARKINSON 1984). The PB/B for the Centropyxidae ranged from 115 to 225, with a mean of 160 for all layers. The amount of carbon respired per year was estimated as: 6.85 g- m- 2 (dry weight) X 47 % (carbon content of amoebae, BAND 1959) = 3.22 g' m- 2. This amounted to 1.19% of the total annual carbon input to the soil for the Centropyxidae. The respiration losses for the Centropyxidae were slightly under 1/3those for the Euglyphidae (LouSIER and PARKINSON 1983), and represented 20 % of the total respiration losses of the entire testacean community, indicating an intermediate role for the Centropyxidae in the aspen woodland soil.
Acknowledgements Financial support for the study was provided by an NSERC Operating Grant (No. A2257) to Dr. DENNIS PARKINSON and an NRCC Postgraduate Scholarship to the author.
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178
.l . D. Lor-sn:n, Population Eoology of Ccntropyxidae
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