A role for belowground biota in plant-plant facilitation

1. Plant-plant facilitation is an important driver of plant diversity, which in turn maintains ecosystem multifunctionality and can buffer some negative effects of climate change. Facilitation is classically attributed to the amelioration of environmental extremes and resource availability. Integrating belowground biota into the positive plant interactions framework should provide a more realistic understanding of this process, enabling us to gain insights into the dynamics of below-aboveground communities. 2. We tested the effect of belowground biota on the performance of a plant community and of individual species using soil extracts from the understory of a benefactor plant species and adjacent open spaces. Soil bacteria from extracts and experimental microcosms were analyzed using pyrosequencing. 3. Soil biota had a significant effect on the abundance, growth, functional traits and reproductive output of beneficiary plant species through processes that are independent of the direct influence of the benefactor species. Different soil bacterial communities were associated with the benefactor species, the individual beneficiary plant species and the plant community revealing complex below-aboveground links between plants and soil microbiota. 4. Synthesis: The belowground biota cultivated by benefactor plant species play a fundamental, previously overlooked, role in positive interactions between plant species contributing to the preservation of diversity and the evolution of plant communities.