Carbon flux through the soil animal food web: meso- and macrofauna
Zusammenfassung der Projektergebnisse
In the present project, the subproject FaunWeb successfully tracked the flux of below- and aboveground carbon through the soil animal food web in an agricultural ecosystem. We were able to assign individual species to distinct feeding channels (fungal or bacterial) and entangled feeding interactions between species, e.g. by enlarging the resource spectrum of species or finding preferences for individual saprotrophic fungal species in fungivores. These results will contribute to the construction of food web models not only in agricultural fields, but will further influence soil animal food web models in general by adding new feeding links and preferences of individual species to the parameters used in the modelling process. During the first funding period, the conducted experiments on the long term and short term incorporation of root and litter derived maize carbon indicated high importance of root derived resources for the soil animal food web in general. Addition of litter derived aboveground resources little affected soil animal abundance as well as the incorporation of plant carbon into soil animal body tissue. Notably, soil animals were mostly affected by season and, in particular, by the identity of the crop plant. While cropping with wheat resulted in high abundances of soil animals in autumn and winter, cropping with maize resulted in low abundances of soil animals at each of the sampling dates. The results suggest that cropping with wheat increases the availability of resources as compared to cropping with maize fields presumably due to high nutritional quality of decaying wheat roots after harvest. To eliminate the potential effect of crop plants on resource utilization of soil animals we established the second field experiment including treatments without plants. Unexpectedly, abundances of soil animals in plots without plants exceeded those in maize plots, indicating negative effects of living maize plants on the soil animal community. Presumably, maize plants reduced the growth of algae and mosses on the soil surface which functioned as important food resource for soil animals and exceeded the role of maize as resource.
