Soil microbial influences over coexistence in multispecies plant communities in a subtropical forest
- Soil microbes are known to substantially affect pairwise plant species coexistence across terrestrial ecosystems. However, projecting soil microbes’ effects on plant coexistence dynamics in diverse, multi-species systems remains a pressing challenge.
- To address this challenge, we conducted a greenhouse experiment with 540 seedlings of five tree species in a subtropical forest in China and used a structural method to evaluate the degree to which microbes promote species coexistence in multi-species systems. Specifically, we grew seedlings alone or with competitors in different microbial contexts, and fitted individual biomass to a population dynamic model to calculate intra- and inter-specific interaction parameters with and without soil microbes. We then used this interaction matrix to calculate structural niche differences (which favor coexistence) and fitness differences (which drive exclusion) for all possible communities assembled with two to five plant species.
- We found that the soil microbes generally increased both the structural niche and fitness differences across all communities, and that microbes had substantially stronger effect on structural fitness differences than on structural niche differences. By evaluating the functional trait correlates of structural niche and fitness differences between plant species pairs, we also found that soil microbes have the potential to change trait-mediated competitive dynamics between plants.
- Synthesis: These findings demonstrate that soil microbes can have drastic effects on multispecies coexistence dynamics between plants, and adds to the experimental evidence that microbes in soils play a larger role in mediating fitness differences than niche differences.