Switchgrass and Its Impact on Soil Carbon Dynamics
Switchgrass (Panicum virgatum) is a perennial grass that produces a deep rooting system (up to 3 m). As a flagship biofuel crop in the United States, more land is converted to switchgrass production across the country. However, it remains unclear how the increases in deeply rooted plants will influence microbial carbon dynamics in deep soils. I explore the amount, stability, and chemical composition of soil organic carbon in soils under switchgrass.
Switchgrass cropland @ Ithaca, NY with Erin and Sravani © Brian Richards
Microbial Resource Acquisitions under Plant Invasion
Soil microorganisms deploy extracellular enzymes to decompose soil organic matter and obtain resources. The amounts and types of microbial extracellular enzymes, thus, influence the stability of soil organic matter. Yet, we do not know about ecological context when microbes adjust their productions and efficiencies of distinct extracellular enzymes. I investigate how substrate landscape (quantity and quality) influences microbial resource acquisition strategies. I employ non-native species plant invasion, soil depth, and texture as a means of varying substrate landscape.
Japanese Knotweed invaded sites @ Amherst, MA © Surendra Bam, Elizabeth Leonard
Land-Use Change and Belowground Processes
Disturbance of terrestrial ecosystems may drive soil changes that extend far deeper and persist far longer than is currently appreciated. If so, large-scale disturbances such as land-use change and fire may serve an unappreciated role as drivers of change in deep soil processes. By sampling deep soils (up to 5 m) across replicated plots at the Calhoun Critical Zone Observatory, I explore how microbial carbon, nitrogen, and phosphorus dynamics change with soil depth.
Calhoun CZO © Christoph Lehmeier
Nutrient Cycling in Boreal Forests
Human-driven climate change is disproportionately impacting boreal ecosystem processes. Nutrient cycling is one of the major processes ecosystems perform, but we have little knowledge about how and how much nutrient dynamics would vary in a warmer world. I study the effects of temperature on microbial carbon and nitrogen cycling and associated greenhouse gas emissions from boreal forest soils in eastern Canada.
Newfoundland and Labrador Boreal Ecosystem Latitudinal Transect © Kate Buckeridge
Microbial Responses to Temperature at Diverse Scales
Knowledge about how temperature will influence microbial decomposition of soil organic matter and resultant CO2 efflux from soils is of importance to understand the global carbon balance and more accurately project future climate. Yet, it is difficult to quantify microbial activities in their natural habitats due to inherent heterogeneity in soils. I use reductionist approaches from pure exo-enzyme assays to a chemostat technique (a continuous culture of microbes) to a soil incubation, such that I can parse the temperature responses of multiple processes operating simultaneously in soils.
Fertilizer and the Stability of Soil Organic Matter
Stability of soil organic matter is key to sustainable agriculture. Yet, little is known about how different management practices would influence soil health and greenhouse gas emissions. Using a soil incubation and a gas chromatography, I assessed the effects of nitrogen additions on the stability of soil organic matter in rice paddy soils. I demonstrated that the dominant form of nitrogen fertilizer can influence microbial exo-enzyme activities (microbial tools to break down soil organic matter), CO2 losses, and bacterial and fungal abundance in soils.
Seocheon, Korea
Janghang Wetland, Korea
Janghang Wetland, Korea