Structural composition of arboreal arthropod food webs across land use change in two seasons using body mass and stable isotopes

Little is known on how the biomass of arboreal arthropods from different trophic groups responds to agricultural practices in tropical land-use systems and how these responses are affected by seasonality. The aim of the proposed research is to study the structure of arboreal food webs across land use systems, and the impact of seasonality on the food web structure in the land use systems studied by EFForTS. We aim to use body masses, inferred from body length and width, and 15N stable isotope measurements to show how energy fluxes between trophic groups differ among the four land use systems Rainforest, Jungle Rubber, Rubber, and Oil Palm, and how they change within each system between the dry season and the rainy season in Jambi. To do that, we rely on previously collected arthropod samples from the first Z02 canopy fogging campaigns in the dry season of 2013 and the rainy season of 2013/2014.
At Bogor Agricultural University, the samples have been taxonomically sorted to order level (some orders even beyond to morphospecies level). Besides, the body lengths and widths of randomly selected and plotwise replicated individuals were measured. Those individuals will be brought to Göttingen University, where they will be subjected to stable isotope measurements at the Centre for Stable Isotope Research and Analysis (Kompetenzzentrum Stabile Isotope, KOSI). Using standard biometric equations earlier developed in EFForTS, we will estimate biomasses of 12 arthropod orders with previously ascribed trophic guilds, and the energy fluxes between them. The predictions resulting from that will be compared to the results of the stable isotope measurements, which also estimate trophic positions. The projected output of this study is a joint publication discussing the structure of food webs across land use systems, and the influence of seasonality on food web structure, involving authors from Bogor Agricultural University and Göttingen University.