Marissa Kopp

Current Projects:

Exploring Control Points of Soil Respiration at Shale Hills Critical Zone Observatory 

Soil CO₂ efflux, the release of CO₂ from soils to the atmosphere, is the second largest flux in the global carbon cycle yet bears the largest uncertainty bounds. Contributing to this uncertainty is heterogeneity in both space and time. Researchers recognize spatiotemporal heterogeneity in soil CO₂ efflux, but practical limitations mean that we cannot always measure every interaction everywhere. Instead, we balance tradeoffs in when and where we monitor by using long-term collocated data from the Shale Hills Critical Zone Observatory, including years of manual soil gas monitoring (maximizing spatial replicates) and continuous hourly monitoring (maximizing temporal replicates). Together, these data have helped to uncover the spatiotemporal patterns that must be captured to understand whole system processes, and we can then target these “control points” to study their drivers or for management intervention.

Exploring Tree Species’ Influence on Soil Gasses at a Common Garden Experiment

There’s a push to plant and preserve biodiverse forests that support many tree species, but how much does one species change its environment? A site dedicated to investigating this question is Penn State’s common garden—an experimental design in which replicated monocultural plots of 16 tree species are managed under shared environmental conditions. By holding these conditions constant, we can test how species’ traits have influenced the surrounding soils over the past 25 years. For example, studies at the common garden have explored the relationship between trees’ belowground and aboveground traits, such as links between species’ root traits and whole-plant functions (McCormack et al., 2012) or between mycorrhizal association and soil nutrient foraging strategies (Chen et al., 2016). Researchers have also shown how species’ traits extend beyond the plant to change surrounding soil chemistry and microbial community composition (Yates et al., 2021). Our ongoing work expands these changes within the soils to what comes out of them. Specifically, we study how tree-mediated changes in soil biology and chemistry lead to differences in when and how much soil gases are emitted, including carbon dioxide (CO₂) and nitrous oxide (N₂O). These are potent greenhouse gases, and by understanding their relationship with tree species, we can better model and predict gas emissions as well as open the possibility of intentionally selecting species that improve both our soil and air quality.