Soil microbiome mediates range-wide phenological clock of a foundation tree species

Background/Question/Methods Identifying the role of the soil microbiome in climate change solutions and in particular plant responses to climate change is a significant research challenge and frontier. For example, phenological events are critical for plant responses to climate change, persistence on the landscape, and for the timing of associated species interactions. In plant-soil research, there is evidence that soil microbiomes may be important to adaptive traits such as phenology. However, integrating spatial scales relevant to climate change with plant genetics and soil microbial ecology is difficult and makes studies of broad inference rare. Building upon previous research in this system showing 1) evolution of bud break phenology of Populus angustifolia and correlated shifts in the tree-associated soil microbiome along landscape-level climatic gradients, as well as a strong effect of plant conditioning on soil microbial communities, we established a reciprocal transplant study of Populus trees collected from across the western US aimed to explore how climate, plant genetics, and soil microbiomes interact to influence plant phenological traits.

Results/Conclusions Our results show that climate-driven variation in the soil microbiome results in functional differences for plant phenology. We provide evidence that climate driven variation in the soil microbiome can mediate plant phenology at landscape scales. If we can begin to further develop frameworks that help partition the effects of climate, plant genetics, and biotic interactions on plant phenotypes and adaptation, we can then begin to provide context on what phenotypes and combination of interactions may allow for survival, persistence, and adaptation in a warming world.