Trophic structure of soil animal food webs of deciduous forests as analyzed by stable isotope labelling

Project A4
Trophic structure of soil animal food webs of deciduous forests as analyzed by stable isotope labeling

supervisor: Prof. Dr. S. Scheu

Project
In the project A4 I analyze the structure of soil animal food webs of deciduous forests. I use stable isotopes and fatty acid analysis because direct observations are not possible due to the small size of the animals.

With natural abundance of stable isotopes we are able to investigate the trophic position of a single species in the food web. Pulse labeling experiments enable us to follow the flux of carbon and nitrogen through the food web. Fatty acid analysis is used to trace basal resources of the soil animal food web.

In cooperation with the projects A1 (Michaela Rath) and B5 (Janine Sommer) we conducted a pulse labeling experiment under controlled conditions in a plant chamber to investigate the carbon and nitrogen flux from trees via roots into the decomposer system for two different tree species (seedlings of beech and ash). With this experiment I am able to follow the root derived carbon and nitrogen into soil animals by stable isotope analysis and disentangle the bacteria versus fungi channel by compound specific fatty acid analysis.

My second experiment deals with the litter derived carbon and nitrogen. A field experiment was conducted in Hainich National Park where labeled leave litter (13C and 15N) was used in a mesocosm experiment. Natural litter was replaced by labeled leave litter from ash and beech to investigate the incorporation into soil organisms.

Methods
Stable isotope analysis (13C and 15N)
NLFA (neutral lipid fatty acid analysis)

Publication

Jochen Fründ, Sarah L. Zieger &Teja Tscharntke, “Response Diversity of Wild Bees to Overwintering Temperatures”, $$ in prep.