Zusammenfassung
Nematode trophic groups were studied in litterbags in a Pinus silvestris
forest using sampling periods of 8 weeks during 2.5 years. Temperature,
moisture relationships and annual periodicity of nematodes were analyzed
in the litter (L), fragmentation (F) and humus (H) horizons. Litterbags
containing L, F and H material were placed in stacks and buried in
the organic layer. Undisturbed core samples were used to compare
the nematode abundance under normal field conditions with that in
the litterbags. Time dependence of population growth and colonization
was also studied in separate litterbags that were replaced every
8 weeks. During the first 4 to 6 months of the experiment, nematodes
in the litterbag stacks grew rapidly to circa 5x106 m-2. After that
period, abundance gradually decreased to about 2.5x106m-2. These
abundances were similar to those found in undisturbed cores. Nematode
abundance during the first year was most pronounced in the top (L)
litterbags; subsequently densities were more or less the same in
the three organic horizons, reflecting the gradual change of L to
F material. On average, during 2.5 years, bacterial feeding nematodes
were the dominant group in the organic horizons (73%), with 17% hyphal
feeders and 9% plant feeders. There were dissimilarities between
layers and in the course of time. The number of hyphal feeding nematodes
differed significantly between layers. In the first 2 to 4 months,
hyphal feeding nematodes equalled the bacterial feeders in the L
layer. Later bacterial feeders became dominant. The highest number
of plant feeding nematodes was found in the F litterbags. Significant
effects of temperature and moisture were mainly found on bacterial
feeding nematodes. Regression coefficients for trophic group abundances
and moisture were generally positive. Temperature was negatively
correlated with the three functional groups in the L horizon only.
Bacterial and hyphal feeding nematodes showed a significant decrease
with time in the L layer, reflecting diminishing substrate quality
(and food availability) during decomposition. A significant annual
periodicity could be demonstrated for bacterial feeders in L litterbags
and plant feeding nematodes in the H material.
Nutzer