Vertical stratification and trophic interactions among organisms of a soil decomposer food web. A field experiment using 15N as a tool
2002
Setaelae, H. ((University of Jyvaskyla (Finlande). Department of Biological and Environmental Science)) | Aarnio, T.
In this field study, the spatial segregation between the litter- and humus-inhabiting organisms of the detrital food web was studied using 15N-isotope technique. The study was established in 11 × 11 m plots fertilized with 15N-labelled urea. Ten years after urea application, soil samples were taken, both from the litter layer and the combined F+H layer. The samples were analysed for N content and the proportion of 15N in the residual organic matter in the litter and F+H layer (excluding microbes), microbial biomass, and various feeding guilds of soil fauna. The basal resource, soil microbes, and the fauna were more enriched with 15N in the F+H layer than in the litter layer. In the litter layer, the 15N enrichment of the expected food source equalled the one of the consumers, whereas in the F+H layer all trophic groups, except microbes and small microbi-detritivores, showed a significantly lower 15N enrichment than their expected food source. The results indicate that large and mobile humus-inhabiting decomposers exploit the overlying litter layer as a feeding site, whereas the feeding of the more sedentary smaller organisms is restricted to the humus layer
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