Changes in the trophic structure of soil animal communities in response to forest management
scientific investigators
Prof. Dr. Stefan Scheu
(Georg-August-University of Goettingen)PD Dr. Liliane Rueß
(Humboldt University of Berlin)(parental leave)
Bernhard Klarner
(Georg-August-University Goettingen)
Hypotheses:
- Species composition of the decomposer community changes in a predictable and consistent manner with forest management.
- Links between decomposers and their food resources change little with intensity and type of land use.
LitterLinks investigates changes in the structure of soil animal communities with forest type and land use intensity. Soil animals form an integral and essential part of terrestrial ecosystems and are closely linked to the aboveground system. Decomposer animals process dead organic matter including plant leaf litter root deposits, root feeders directly influences plant growth and soil engineers such as earthworms alter the structure of the soil thereby enhancing nutrient mineralization and plant nutrient capture. The services of the soil animal community provided for the functioning of ecosystems and for humans are diverse, nevertheless, the interactions and regulatory forces in decomposer systems are poorly understood. This is due to methodological difficulties including the opaqueness of the soil, the small size of soil organisms making their identification difficult and the fact that the assessment of density, biomass and species richness is laborious.
The work of our project intends to identify key taxa in litter and soil of forest sites with different land use type and to investigate changes in community composition and species diversity. For this purpose soil animals are extracted from soil cores by heat and determined to species level. The determination is done by the PhD, master and bachelor students. Contributions of other projects complement the work. Oribatid mites are investigated by Georgia Erdmann (Frass), protozoa by Jan Weinert (NanoFauna) and woodlice by Roswitha Ehnes (ModelWeb).
Data on additional biotic and abiotic factors including microbial respiration, acidity of soil and litter and the thickness of the litter layer have been measured allowing the characterization of land use types and interpretation of site specific differences.
After the determination of species we will analyze the food relationships between representative soil animal taxa, their trophic position and basal food resource by employing three methodologies complementing each other:
- Stable isotope analysis (13C/12C and 15N/14N ratios) of soil animals and potential resources (e.g. leaf litter) allows evaluating the basal resources of food webs and the trophic position of species in food web.
- Fatty acid analysis traces the incorporation of fatty acids from food into the body tissue of an organism. By analyzing fatty acid patterns bacterial and fungal food chains are separated.
- Molecular gut content analysis detects DNA fragments of prey in the gut of predators and allows to trace prey species.
Data on density, biomass and trophic interrelationships of key taxa will be used to establish empirically based food web models by the project ModelWeb. This will allow to uncover the structure of decomposer communities in European beech forest soils in unprecedented detail and to evaluate the impact of forest management on the structure and functioning of decomposer systems.
