WHY STUDY PLANT-SOIL FEEDBACKS?
From local to global scales, plants sequester vast amount of carbon, mediate oxygen cycling, and provide habitat to multitudes of biodiversity. Similarly, the soil microbiome has long been recognized for its importance for a variety of ecosystem services, including nutrient cycling, soil moisture mediation, and litter decomposition.
We've come to learn that the realm of interactions of plants and their associating soil is a dynamic place. At multiple taxonomic scales (families, genera, species, even genotypes) different plants uniquely condition the biotic composition of soils through variation in rhizodeposition, yielding different soil microbial communities. In turn, soils uniquely affect plant success by either facilitating or inhibiting development of similar plants. These positive and negative feedbacks influence much of the plant community structure seen across biomes.
Studying the complexity of plant-soil feedbacks (PSFs) deepens our understanding of how ecosystem function is influenced by seemingly inconspicuous local above-belowground interactions.
What is the overall strength of soil microbial mediation of plant phenotypic variation across plant species?
Despite evidence for dominance of negative plant-soil feedbacks on the landscape, direction of PSFs has been found to vary with plant phylogeny and between early successional and late successional plant species. This variation of plant phenotypic response to conspecific- and heterospecific conditioned soil between species likely suggests that the overall importance of the presence of the soil microbiome for plant phenotype varies across plant species as well. Identifying how the soil microbiome influences different suites of plant phenotypes such as growth, physiology, reproduction, and identifying interspecific variation in phenotypic response to the soil microbiome will enhance our understanding of which plant species are sensitive to the soil microbiome.
Identifying functional linkages between the soil microbiome and plant phenotype
While plant phenotype has traditionally been recognized as the product of interactions between a plant's evolutionary history and the abiotic environment, recent explorations of the immense microbial diversity in soil have uncovered an additional reservoir of genes and functions at the root-soil interface available to plants. While plant-soil feedback studies have provided foundational understanding for broad mechanisms of plant community structure and single-inoculation studies have pinpointed specific roles of individual microbial taxa, little research has examined the role of microbial community aggregate functions on particular plant phenotypes. We use observational field studies and reciprocal transplant greenhouse experiments to explore how variation in soil microbiome taxonomic and functional composition influences plant growth, physiology, and reproduction trait responses to differentially-conditioned soil microbiomes.
Plant-soil microbiome interactions along gradients of fire disturbance
As global change accelerates, natural disturbance events like wildfire are predicted to increase rapidly. Fire fundamentally alters ecosystem functions, many of which are mediated by interactions between plants and rhizosphere soil microbial communities. Identifying how wildfire affects interactions between plants and soil microbes is paramount to predicting important plant-soil contributions to ecosystem functioning following disturbance events. Using a burn severity gradient from a 2016 wildfire in Great Smoky Mountains National Park, we are examining how burn severity impacts soil microbiomes, plant-soil interactions, and subsequent plant success on the post-disturbance landscape.