Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function

The positive relationship between plant diversity and ecosystem functioning is likely to be co-determined by aboveground–belowground multitrophic interactions. Considering and manipulating such interactions thus is likely to significantly improve the mechanistic understanding of BEF relationships. The present proposal comprehensively investigates long-term (>4 years) plant diversity effects on soil microorganisms, nematodes, and other soil invertebrates across different ecosystems (grassland and forest ecosystems) and global change contexts (elevated [CO2], N deposition, warming, and drought) to identify general mechanisms. Complementary and well-directed laboratory experiments will be conducted to simulate soil feedback effects resulting from plant diversity-induced changes in soil food webs. This novel approach will allow investigating the balance between negative and positive plant-soil feedback effects and the consequences for ecosystem functioning. This holistic knowledge of changes in and interactions of above- and belowground processes is crucial to predict the long-term consequences of plant community simplification for ecosystem functioning. Experimental work will be complemented with the meta-analysis of previous work in order to reconcile prior inconsistent findings. The main objective of the present proposal is to disentangle the driving forces of plant diversity effects on soil biota as well as subsequent positive and negative feedback effects on plants. In order to achieve this, the present project has four major goals: (1) investigate long-term plant diversity effects on soil biota and functions across multiple settings in order to derive general conclusions; (2) investigate the significance of plant diversity-induced positive and negative soil feedback effects on plant performance; (3) investigate if anthropogenic stressor effects reinforce plant diversity effects on soil biota and subsequent soil feedback effects; and (4) synthesize results and perform meta-analyses to understand and reconcile inconsistent findings of previous studies on plant diversity effects on soil biota, and relate subsequent changes in soil food webs to alterations in ecosystem functioning