Analysis of root traits to test for environmental filtering and niche complementarity in grassland communities

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While the preceding project BE RICH predicted species performance in a recipient community from the whole regional species pool based on aboveground traits, BE LOW will change the perspective and take on the newcomers' perspective, aiming at predicting in which local neighbourhood a newcomer might perform best. We will have a particular emphasis on traits with a functional link to belowground processes, and thus analyse root traits and exudates, including a broad spectrum of low molecular organic compounds exudated by plants. We will test the hypotheses that (H1) survival and performance can be predicted from the statistical probability of co-occurrence of a species in a specific local neighbourhood, (H2) community-weighted mean traits and functional diversity is related to land use intensity, (H3) the leaf economics spectrum is related to the root economics spectrum. In addition, we will test that (H4) in a specific environmental setting there is a defined degree of trait similarity to the resident neighbourhood community at which performance is maximized, caused by a balance of environmental filtering versus competition by limiting similarity. Furthermore, we hypothesize that (H5) root trait values and root exudation patterns are adjusted to the local neighbourhood and to land use, (H6) certain root trait values and exudates result in a change in soil conditions with time and (H7) that root exudate composition is plant species-specific, and in particular grass species differ from herb species. We plan to use ten species each of mycorrhizal and non-mycorrhizal species as well as ten species each of grass and herb species, in total 20 species, studied both in the field and in the greenhouse. For ten of them we will analyse root exudates. The project will consist of four work packages, which will comprise raising plants and analysis of the local neighbourhood (WP1), planting phytometers of the 20 species into a selection of 54 grassland plots (3 exploratories, 3 land use types, 6 replicates), monitoring their growth and assessing their anatomical, morphological and chemical root traits at the final harvest and using these data to predict assembly rules (WP2), conducting glasshouse experiments in pots for root trait analysis (WP3), and analyzing exudates and roots for mass spectrometry-based non-targeted metabolite analysis (WP4).In summary, we bring together functional biodiversity research, community ecology and functional root research to fill an important gap between above- and belowground processes.