Plant functional traits are metrics for quantifying plant contributions to ecosystem services and functions, therefore predicting how plant contributions respond to climate change requires understanding the drivers of plant phenotype. Traditionally, the significance of the belowground biotic environment to plant phenotype has been overlooked. A growing body of research, however, has found that plant traits including aboveground biomass, photosynthetic rates, and flowering time vary depending on the soil microbiome. To date, these belowground microbially-mediated plant traits have been identified from examining the effect of the aggregate soil microbiome associated with plants without understanding the specific functional contributions of the hyper diverse soil microbial community. Identifying soil microbial functions that influence plant phenotype will provide deeper understanding for how local aboveground-belowground interactions impact plant responses to environmental change, and enable more accurate predictions of plant contributions to ecosystem function. Using a reciprocal transplant greenhouse experiment of three species of the phenotypically-diverse and dominant perennial genus Solidago, we sought to identify the effects of functionally distinct soil microbiomes on a suite of plant phenotypes. We collected soil beneath naturally-occurring S. gigantea, S. caesia, and S. flexicaulis populations, and grew each species in conspecific and heterospecific soil for the entire growing season.
Results/Conclusions
Response of phenotype to microbiome source (conspecific-conditioned or heterospecific-conditioned soil) varied between the three Solidago species. S. gigantea formed flower buds 3 weeks earlier when grown in microbially-active conspecific-conditioned soil compared to microbially-inactive conspecific-conditioned soil (p = 0.07), suggesting a microbiome “home field” advantage for S. gigantea budding time. S. caesia gained 15% in stem diameter when grown in microbially-active S. flexicaulis-conditioned soil compared to microbially-active S. gigantea-conditioned soil (p = 0.05), suggesting a microbiome of a closely related species (S. flexicaulis) confers greater benefit for stem diameter than a microbiome of a distantly related species (S. gigantea). Subsequent metagenomic analyses will assess microbial composition within conspecific and heterospecific soil treatments to identify specific microbial functions associated with this plant phenotype variation. Overall, our results show that 1) the importance of the soil microbiome varies for plant phenotypes and 2) changes in microbiome source can yield shifts in plant phenotype. These findings provide a foundation for which to explore how belowground biotic composition a) can enable more accurate predictions of plant contributions to ecosystem function and b) impacts plant responses to environmental change.