Research
My research centers on how plants and microbes influence ecosystem carbon and nutrient cycling. Specifically, I seek to understand the fundamental processes controlling soil organic matter (SOM) formation and decay, and how ecological phenomena interact with these processes in a changing world. I work towards this objective at scales ranging from microcosm experiments to global data syntheses using a variety of approaches. My overarching philosophy as well as specific research themes are detailed below.
Research Philosophy
Advancement of ecological understanding is achieved through three complementary approaches. Experiments are necessary to determine causal relationships. Observations of natural ecosystems uncover patterns and establish ecological relevance. And models formalize our collective knowledge and serve as tools for making predictions. Ecosystem science advances most rapidly when these approaches are working in concert. I seek to integrate across these “ways of knowing” in my own research and to instill this philosophy in students and mentees.
The real "research triangle"
Biotic mechanisms of soil carbon formation and decay
Soils are one of Earth’s largest carbon reservoirs and, while soil carbon can be thousands of years old, it is increasingly recognized that a large portion of soil carbon is dynamic and vulnerable to environmental changes. A major objective of my dissertation research was to understand the extent to which microbial physiological traits mediate the conversion of plant inputs into stable soil carbon. I approached this objective using stable isotope techniques along observational gradients and in a laboratory experiment. This work was funded by a NSF-DDIG and a manuscript is in preparation.
A field decomposition experiment using isotopically labeled leaf litter. Collaborative project with Adrienne Keller
Multi-hypothesis soil carbon modeling
Soil carbon models are needed to make predictions about and manage the carbon cycle, yet models remain highly uncertain. Most of this uncertainty is likely due to the fact that different models represent different hypotheses about the nature of soil carbon formation and decay. In my postdoctoral research, I am probing this process uncertainty in order to develop more general soil carbon models. Currently, I am evaluating whether biotic mechanisms could help explain why soils appears to have a maximum capacity to store carbon.
Presentation given at the 2020 Ecological Society of America annual meeting.
Mycorrhizal associations and soil organic matter in forests
Almost all temperate tree species associate exclusively with one of two types of root-associated mutualistic fungi: arbuscular mycorrhizae (AM) or ectomycorrhizae (ECM). These fungi and their associated trees differ in traits that are important drivers of ecosystem functioning. Funded by a grant from the Smithsonian Center for Tropical Forest Science, I have explored how mycorrhizal associations relate to the storage and stability of soil organic matter across multiple Eastern US forests.
Field crew enjoying some well-deserved lunch-on-a-log in a northern Wisconsin forest.
Invasive plant impacts on ecosystem functioning
I have long been interested in how invasive plants affect ecosystem functioning and how these effects vary depending on environmental context. My work in this area has focused on how the invasive C4 grass, Microstegium vimineum, affects decomposition, nitrogen cycling, and soil organic matter properties across multiple sites and environments (e.g. urban versus rural forests, and differing invaded communities). I have had the pleasure of mentoring multiple students in independent research on this topic. Their work looked at invasion effects on soil carbon, earthworm communities, microbial enzymes, and mycorrhizal colonization. Two of these students are now co-authors on published papers.
Student, Robin Johnson, sampling in a M. vimineum patch in Indiana.