Aboveground plant-insect interaction webs and associated processes along a plant diversity gradient

Pollination is most critical to plant reproduction and plant diversity is important to attract high pollinator diversity and pollination frequency. However, it has rarely been studied how flower traits, pollination, and other biotic interactions affect plant reproduction under a scenario of plant biodiversity decline. In this subproject, the following main objectives will be addressed: (1) Chemical flower traits will be measured and used together with morphological flower traits to explain the diversity and frequency of flower visits along the long-term plant diversity gradient; (2) The stoichiometry of mutualistic pollinator-flower interactions will be addressed by comparing C:N:P ratios of pollinators with the reproduction success of pollinators in the main experiment; (3) Flower visitation and plant-pollinator interaction webs will be analysed in the main and the (new) trait-based experiment including the integration of invaders in plant-pollinator interaction webs; (4) Plant species-specific responses to pollination and plant reproduction will be studied in the (new), trait-based experiment; (5) Hand- versus bagged pollination treatments applied in a greenhouse experiment will identify the breeding systems (autonomous self- versus cross-pollination) of major flowering plant species of the Jena experiment. The subproject will collect plant-specific traits (i) to explain flower visitation, pollination, and plant reproduction, and (ii) to add flower traits to the overall trait-based modelling. The subproject is therefore critical to understand plant reproduction dependent on plant diversity, and hence to understand plant population dynamics in grasslands that differ in plant species richness.