SP09c Termite diversity and ground food webs in relation to decomposition in a subtropical forest diversity gradient (FOR891_sp09c termites)

The accumulation and decomposition of wood and leaf litter in the forests have been extensively studied and reviewed in the world. Grazing of dead wood and plant litter by soil invertebrates are highly dominated by termites and ants, constituting the main biotic agent of litter loss in tropical or subtropical forests. Through their diverse feeding and nesting activities, termites become key mediators of pedological and ecological processes and play key roles in decomposition processes, nutrient cycling, nitrogen fixation, carbon flux, soil creation and soil distribution. These functions are largely dependent on the species composition and diversity of the termite assemblage. Dead wood and plant litter are an extremely diverse material and their decomposition is an equally varied process. Different tree species produce wood of widely different hardness and chemical composition both of which affect its palatability to termites. So which kinds of chemical components affect termites’ food preference and the plant-termite food web structure becomes a key issue for us to understand the decomposition process. The German twin subproject concentrates on above-ground, multi-trophic interactions and food web ecology of two linked study systems, (i) trap-nesting hymenoptera and (ii) ant-aphid and ant-parasitoid-hyperparasitoid interactions. We plan to tightly link our field work with our German partners to focus on the impact of ants on the plant-termite food webs and decomposition rates. Since ants are important termite predators, the density of ants is expected to negatively affect the termite community and their mediated role in the decomposition process. Besides describing multi-trophic interactions, the German projects propose to study the concentration and diversity of sugars and amino-acids of the aphid honeydew to understand chemical mechanisms driving the relationships between diversity and functioning. We will use dried leaf samples of fresh and litter material to analyze total sugar and nitrogen concentration to study how these chemical components affect the termite-community and decomposition rates. Therefore both projects focus on chemical mechanisms driving BEF relationships besides studying the link between above-ground and ground food webs as drivers for ecosystem functioning. In summary our sub-project proposes to (1) study the composition and distribution of termites in this region, (2) which kinds of chemical components are key factors to determine food preferences by termites, (3) assess the contribution of termites to decomposition of dead woods or plant litters in subtropical forests. Our research is therefore not only linked to our twin project but also tightly linked to all sub-projects focusing on the understanding of decomposition processes.