Climate change is altering plant species distributions and thus interactions among other species. Soil-microbial interactions have the potential to mediate the ability of plant populations to persist in their current location or establish in new areas. Plants may migrate with their historical microbial communities or create relationships with foreign microbial communities due to mismatched migration rates. In particular, immigration of microbial taxa from drier or warmer conditions may promote seedling tolerance to drying or warming local climates. We tested whether 1) tree seedlings performed better when inoculated with microbial communities that were local or foreign to the abiotic soil conditions, and 2) microbial communities sourced from drier areas can promote seedling growth in drought conditions.
We collected live soils from nine sites over a gradient of precipitation in the Midwest US. We then sterilized a portion of each soil via irradiation, while retaining a portion as a living microbial inoculum. In a greenhouse experiment, we measured seedling biomass of Ostrya virginiana and Betula nigra seedlings after experimentally swapping sterilized soils and local and foreign microbial inocula. To simulate water-stressed conditions, half of the pots were watered to saturation weekly, while the other half were water every other week.
Results/Conclusions
1) In well-watered conditions, plants performed best when the microbial inocula was sourced from the same site as the abiotic soil background, compared to microbial inocula sourced from sites west or south of the abiotic soil source. 2) Growth in water-stressed conditions was maximized when pots were inoculated with microbes from drier sites. In water stressed, but not well watered, conditions, seedling biomass was positively correlated with the aridity index of the site from which the microbial inocula was sourced.
These results suggest that extirpation of local microbial taxa, and/or immigration of novel microbial taxa to a site may be detrimental to plant growth due to mismatches between microbes and soil conditions. However, immigration of drought adapted microbial taxa may also provide additional drought tolerance to plant populations facing drying conditions. This work contributes to the understanding of how microbial interactions that may potentially exacerbate or mitigate challenges to plant populations caused by climate change.