Plant-herbivore-predator food webs, stoichiometry and functi

The extinction of species can affect natural food webs and may also have impacts on functions of entire ecosystems. Experiments that investigate plant species loss so far rarely consider the effects on other species via food webs. Especially how nutrient, biomass or energy flows to herbivores (plant-feeding animals) or predators (animal-feeding animals) change when plant species (e.g. trees) disappear from ecosystems is unknown. Here we will study plant-herbivore-predator food webs in a tree diversity experiment in China (BEF-China). Our central hypotheses are: (1) The loss of tree species affects plant-feeding insects (herbivores) more than predators that feed on these herbivores and thus, biomass will be distributed differently in food webs where tree diversity is low. (2) Low carbon:nutrient ratios in plants where tree diversity is low will also emerge in herbivores and their predators. (3) Food webs in forests with lower tree diversity have less energy stored in each organism group and less energy also flows between organisms that feed on each other. (4) The changing structure of the food webs (i.e. who eats who) can help to explain how the loss of tree species affects entire ecosystems. In the core plots of the BEF China tree diversity experiment we will use insect traps in the forest canopy and also on the ground to record insect and spider species and will measure the body size and carbon and nutrient contents of certain species. We will furthermore assess herbivory and pathogen infestation by scanning the leaves for damage and will use artificial caterpillars made from clay to measure predation rates in all core plots. In selected plots, we will use fogging with insecticides as well as barcoding of gut contents to understand which species eats which other species and to construct their food webs. Moreover, we will analyse more nutrients (e.g. carbon, nitrogen, phosphorus, calcium, potassium, magnesium, sodium, manganese, iron) in the bodies of selected herbivore and predator species. We will extend previous work by including more groups in the food webs and by investigating biomass and energy distributions in the food webs as well as their nutrient contents and we will study the effects of tree diversity on these food webs. Certain detailed food webs will be constructed (i.e. who eats who). We will use new methods in the BEF-China Experiment (stoichiometry, gut content barcoding) and will collect insects and spiders from different layers in the forest using new collection methods.