Symbiotic nitrogen fixation in Neotropical forests
Symbiotic nitrogen (N) fixation occurs between a subset of plants and N-fixing bacteria, and takes N from the atmosphere and converts it into a form of N that plants can use. Nitrogen is an important building block to life and can limit plant growth in both natural and agricultural settings. Symbiotic N fixation (SNF) is the largest non-anthropogenic N input in many terrestrial ecosystems and may influence how these forests function and respond to disturbance or a changing climate. My work focuses in the Neotropics, where legumes (a subset of plants that partner with N-fixing bacteria) can be found in high abundance. I use a combination of greenhouse studies, field experiments and observations, and DNA sequencing techniques to understand how environmental conditions (light, soil nutrient and/or water availability) and partner identity (plant and bacteria species) affect the mutualistic relationship between legumes and N-fixing bacteria. In particular, I am interested in (1) quantifying how disturbances like canopy gaps (which alter local environmental conditions) affect how much N this mutualism can bring into Neotropical forests and, (2) disentangling the mechanistic drivers of this "canopy gap" effect. I am currently working with collaborators to integrate field-based measurements of SNF in canopy gaps with remote sensing data (LiDAR) to create the first robust landscape-scale SNF estimates that accounts for this "canopy gap" effect.
The role of deer and microbes in Northeast forest recovery
Oak trees are a foundational species to many forests in the Northeast of the United States and Oaks primarily form mutualistic relationships with ectomycorrhizal fungi. Many ecological processes have lead to a general decline in Oak populations at the seedling and sapling stage in these forests, which will likely influence the future tree community composition. For example, the removal of Oaks may favor other tree species in these forests like Red or Sugar Maples, which tend to form relationships with arbuscular mycorrhizal fungi. I seek to understand how deer browsing interacts with tree community recovery to affect mycorrhizal fungi community composition by utilizing a large experimental manipulation at Black Rock Forest, which removed Oak trees and set up deer exclusion plots 10+ years ago. As the dominant tree species community shift, so may the dominate mycorrhizal type. This would influence how nutrients cycle through these forests, having implications on the growth and carbon capture potential of Northeast forests. This project utilizes DNA sequencing techniques to characterize mycorrhizal community composition while linking these data to soil nutrient analyses and tree species composition to understand how ecological interactions between trees and fungi affect the biogeochemical cycling of these forests.
Belowground biomass characteristics and responses to global change
Much of my research program tries to increase our understandings of processes occurring below the soil surface across ecosystem types. These questions span from understanding how abiotic and biotic factors relate to root biomass in high-latitude ecosystems to understanding how plants allocate resources to patches of soil nutrients in greenhouse experiments. I am also a contributing member to the Tropiroot team that compiles and synthesizes data from tropical root studies to better understand tropical root trait patterns across time and space while also assessing root trait responses to global change.
Tripartite symbiosis dynamics (Plants | N-fixing bacteria | Mycorrhizal fungi)
Our understanding of mutualistic interactions between organisms is primarily based on work that studied these mutualisms in isolation. However, many (if not most) organisms form multiple mutualistic relationships at any given time and these relationships influence how organisms interact with their environment and other partners. Many legumes can form simultaneous mutualistic relationships with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi. The bacteria provide plant-available nitrogen and the arbuscular mycorrhizal fungi can provide other soil nutrients (such as phosphorus) and may help with water stress. In exchange, the plant provides both microbial symbionts with sugars (carbon) that the plant has fixed through photosynthesis. There is likely a tradeoff between these two microbial symbionts because they are both large carbon costs to the plant, and both microbial symbionts can influence how nutrient cycle through ecosystems. I use greenhouse studies and field experiments to understand how environmental conditions influence how plants invest in these two microbial symbionts and what impact this has on plant growth and survival.