Impact of soil negative feedbacks on plant-species diversity

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Recent research indicates that plant-soil feedbacks may contribute to explaining a large proportion of the relative abundance of plant species in communities and therefore to mechanisms enabling species coexistence. We wish to use the framework of the Biodiversity Exploratories to test two main hypotheses: (1) that plant species with large individual biomass production that are not locally dominant are most strongly limited by specific negative soil feedbacks; and that (2) potentially invasive plant species profit from the absence of specific soil-negative feed-backs in their new habitat. These two hypotheses will be examined by two different sets of plant species, which show the relevant variability in the traits examined, i.e. for (1) biomass and relative abundance, and for (2) occurrence along a South-North gradient in the Exploratories. For these tests, we will use soil microbial samples from all 50 experimental grassland plots. In greenhouse experiments, we will additionally provide mechanistic resolution regarding the nature of the soil (negative) feedback, by examining different soil fractions, including arbuscular mycorrhizal fungi, root pathogenic fungi, and a microbial mish (mixture of pathogens and saprobes). Additionally, we will test FTIR, a new and high-throughput fast analysis of root material, which could subsequently be utilized also for other projects in the Exploratories that are faced with large sample numbers. With our large-scale and phylogenetially diverse screening, we hope to make an unprecedented contribution to the study of mechanisms enabling plant species coexistence and biodiversity; this knowledge can be integrated with other soil biota and plant-focused projects in the Exploratories.