PS 5-66 - Microbe-mediated Drought Response in Plant Communities

Abstract: The presence and history of soil microbial communities can affect plant stress responses. For example, microbial communities from drought environments have been observed to protect plants undergoing drought stress. A majority of studies have focused on single species; however, effects at a community level have yet to be thoroughly investigated. We asked how plant communities facing drought stress will differ in productivity when inoculated with microbe communities that have evolved under drought compared to well-watered conditions, as well as how biomass and trait responses vary across species.

Using soil samples collected from a rainfall manipulation experiment at the long-term ecological research site at Kellogg Biological Station, we created inoculants from treatments that had experienced drought in 2021, drought in 2022, or ambient rainfall conditions. We used these to establish a greenhouse experiment with simulated early successional grassland communities. After 14 weeks of growth in either well-watered or droughted conditions, measures of productivity were taken to determine the community’s response to drought stress and whether and how microbial community history affects these responses.

Total productivity, measured as biomass, was lower in drought greenhouse treatments (P < 0.0001) but was not affected by microbe history (P = 0.49). However, microbe mediated plant responses to drought stress varied greatly by species. Within the community, two of eight species showed strong responses to the microbe treatments. Height and specific leaf area measurements increased significantly when these species were grown under watering conditions (i.e., drought or non-drought) that matched their respective microbial community’s history. Biomass measures, while not significant, showed similar trends in these species. Our findings suggest some species will perform better when inoculated with microbes that evolved in environments with similar stress conditions. While this was not true across all species, it may provide evidence that species responses to stress vary across a community, with some species responding more drastically to varying microbial history than others. This variation in stress response could potentially alter community composition over time.