Interactions between plants and soil microbes play an important role in structuring terrestrial ecosystems by influencing plant growth and competitive ability. Abiotic conditions such as varying nutrient levels or environmental stress can alter the direction and magnitude of plant–microbe interactions. It is therefore possible that the effects of changing climates, including changing water availability, could alter the outcome of plant–microbe interactions, which could in turn affect interactions among plant species.
In a recent Editor’s Choice article published in AoBP, Hawkins & Crawford test whether water availability mediates the effect of soil microbes on plant interactions in the Texas coastal prairie using a controlled greenhouse experiment with three plant species: Schizachyrium scoparium, Rudbeckia hirtaand Plantago lanceolata. To test for an interaction between water availability and soil microbes, plants were grown in either live or sterile soil treatments and with high, medium and low water availability. They found that soil microbes and water availability influence the outcome of competition between plant species. Overall, the soil microbe additions tended to increase the strength of competition between members of the same species relative to competition between members of different species, especially when water availability was low. Because competition between members of the same species was generally stronger in the presence of soil microbes, the authors conclude that soil microbes may play a role in promoting coexistence among species, particularly under drier conditions. The outcomes of this study suggest that a better understanding of how the environment influences plant-microbe interactions will allow us to better predict dynamic changes in plant communities under a changing climate.