Plant-herbivore-predator food webs, stoichiometry and functions

• Applicant: Professor Dr. Andreas Schuldt
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452861007

Wider research context: Species loss has been shown to cascade to different food web levels and may affect functions of the entire ecosystem. Plant diversity experiments so far rarely consider multitrophic effects or only focus on changes in abundance or species richness, ignoring effects on stoichiometry, intraspecific traits or potential shifts in biomass pyramids and energy fluxes in the networks. Hypotheses: Here we propose to study plant-herbivore-predator food webs along a tree diversity gradient in the BEF-China experiment. Our central hypotheses are: (1) Tree diversity effects on abundance and species richness decrease with increasing trophic level and this leads - together with changes in intra- and interspecific body size distributions - to shifts in trophic pyramids. (2) Intraspecific changes in carbon:nutrient ratios of herbivores and predators can be observed with increasing tree diversity, reflecting increased nutrient availability in plant tissues (within and across species). (3) Multitrophic plant-herbivore-predator energy networks show higher stocks (standing biomass) and fluxes (herbivory, predation) across trophic levels at higher tree diversity. (4) Structural properties of highly resolved plant-herbivore-predator networks provide more detailed mechanistic explanations of how plant diversity loss affects ecosystem functioning.Methods: In all core plots, we will use flight-interception and pitfall traps to record arthropod diversity and will measure the body size as well as carbon and nitrogen contents (collaboration with SP2) of selected species (WP1). We will furthermore quantify herbivory and pathogen infestation by scanning the leaves for damage and will use artificial caterpillars to measure predation rates in all core plots (WP2). In the VIP plots we will use fogging with insecticides as well as barcoding of gut contents (done by our Chinese collaborators) to establish species-specific plant-herbivore-predator networks. Moreover, we will analyse an extended stoichiometry (e.g. C, N, P, Ca, K, Mg, Na, Mn, Fe) for selected herbivore and predator species (WP3).Innovation: We will extend previous work by including three trophic levels and by linking these multitrophic communities and their interactions with biomass distributions and stoichiometry to enable an analysis of trophic pyramids and energy-based networks along a tree diversity gradient. We will also record tritrophic species-level networks along the tree diversity gradient for selected tree species. We will use novel methods in the BEF-China Experiment (stoichiometry, gut content barcoding) and will collect arthropod groups from other vegetation strata than before using multiple collection methods.Primary researchers involved: This project will be conducted by Petermann (PI, Salzburg) and Schuldt (Co-PI, Göttingen), in collaboration with our Chinese partners (Chesters and Wang, Chinese Academy of Sciences) and with Buzhdygan (Berlin).

• DFG Programme: Research Units
• Subproject of: FOR 5281: Multi-Trophic Interactions in a Forest Biodiversity Experiment in China
• International Connection: Austria, China
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Co-Investigator: Oksana Buzhdygan, Ph.D.
• Cooperation Partners: Professor Dr. Douglas Chesters; Professorin Dr. Jana Petermann; Dr. Ming-Qiang Wang