Using body mass and stable isotopes to uncover canopy arthropod food webs across a land use change gradient

Many ecosystem functions depend on food web structure, which heavily relies on the biomasses of different trophic groups. However, 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 finalize the study of arboreal food web structure across land use systems, as funded before by EFForTS scholarship in Research Project RP44.
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, 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 dry season 2013 and rainy season 2013/14, which have been taxonomically sorted to order level (some orders even beyond to morphospecies level) and of which a randomly selected, plot-wise replicated number of individuals’ body lengths and widths have been measured at Bogor Agricultural University. 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 Isotopen, KOSI). Using standard biometric equations used earlier in EFForTS, we will estimate biomasses of 17 focus arthropod groups (11 orders, 4 beetle families, parasitoid wasps and ants) 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.