Linking plant evolution with soil microbial processes in coastal marshes

Coastal marshes are among the most productive ecosystems on Earth, providing valuable services that are increasingly threatened by human-induced environmental change. Anthropogenic pressures can negatively impact constitutive biota, like coastal vegetation and soil microorganisms capable of governing ecosystem processes such as biogeochemical cycling that determine the availability of valuable services (e.g., storm protection). Despite its potential importance, efforts to forecast the state and fate of coastal marshes thus far rarely account for the impact that anthropogenic pressures may have on plant-microbe interactions. We are investigating how soil microbial processes (e.g., functional diversity) are influenced by plant evolution (i.e., genetically based trait variations) under conditions of environmental change. Leveraging 100+ year old seed banks of Schoenoplectus americanus, we are examining if differences in plant traits arising from different genetic identities of an ecologically-important salt marsh plant contribute to differences in soil microbial processes under the interactive effects of elevated nitrogen and salinity.

Ecological drivers of plant-microbe interactions in wetlands

Wetland ecosystems provide critical and important functions such as organic matter decomposition and nutrient cycling. Soil and endophytic (microbes inside plant tissues) microbial communities can regulate these functions. Yet, our understanding of the processes underlying the assembly and functions of these microbial communities remains limited. I examine the relative influences of a suite of biotic and abiotic factors on the distribution, diversity and structure of fungal and bacterial communities within the rhizosphere, root and leaf endosphere in two wetland plant species: Taxodium distichium and Spartina alterniflora. Collaborating with scientists from other institutions, this project aims to assess how the root endosphere and rhizosphere soil microbes associated with T. distichium are shaped by their environment along a gradient of salinity. In addition, this project also aims to characterize potential linkages between functional trait variations in S. alterniflora and its rhizosphere microbial communities.

Microbial mediation of salt marsh plant response to salinity stress

Contemporary global environmental change is giving rise to conditions, including a warming climate, saltwater intrusion and sea level rise that present novel challenges to plants and associated microbial communities. While there are increasing evidence suggesting that plants are capable of weathering environmental change through their associations with root and soil microbes, it remains unclear, however, how plant-associated microbiomes confer greater capacity for plants to better tolerate and persist under environmental stress. With collaborators at Smithsonian Environmental Research Center and University of Notre Dame, we use ‘resurrection’ ecology – germinating and growing seeds from century-old seed banks of Schoenoplectus americanus, a dominant wetland grass in the Atlantic coast to determine how microbes can confer better tolerance to salinity stress for the S. americanus. We also examine whether this microbial mediation of plant responses to elevated salinity is contingent on the environment and factors intrinsic to the host (e.g., functional trait variations, genetic lineage – ancestral vs descendant genotypes).

Impacts of the Deepwater Horizon Oil Spill on fungal microbiomes in salt marshes

Large-scale environmental disturbances such as oil pollution can alter the diversity and composition of microbiomes, yet remarkably little is known about how disturbance alters plant-fungal associations. Using Next-Generation sequencing of the 18S rDNA internal transcribed spacer (ITS1) region, we examined outcomes of oil exposure on aboveground leaf and belowground endophytic root and rhizosphere fungal communities of Spartina alterniflora, a highly valued ecosystem engineer in southeastern Louisiana marshes affected by the 2010 Deepwater Horizon accident. This study offers novel perspectives on how environmental contaminants and perturbations can influence plant microbiomes, highlighting the importance of assessing long-term ecological outcomes of oil pollution to better understand how shifts in microbial communities influence plant performance and ecosystem function.