We are working to resolve the effects of geology, topography, disturbance and climate change on soil carbon and nutrient dynamics in Appalachian forests.
The flux of carbon dioxide (CO2) from soils to the atmosphere is one of the largest components of the global carbon cycle. In forests, this flux varies tremendously in space and time. Discovering the source of this variation is important for scaling up plot-level soil respiration measurements and refining regional and global carbon models. At the Susquehanna-Shale Hills Critical Zone Observatory, just 20 miles from the University Park campus, we have monitored soil CO2 concentrations and fluxes on concave and planar slopes along transects from the ridge top to the toe slope. Often, we couple CO2 data with co-located measurements of soil temperature, water, oxygen, and nitrous oxide. And, the geologic matrix of the ridge and valley physiographic region has enabled us to compare Shale Hills (acidic shale bedrock) to nearby soils developed on sandstones and calcareous shales.
These measurements have increased our understanding of how geology (Hodges et al. 2019), and topography (Kopp et al. 2022; Hasenmueller et al. 2015), control the accumulation of CO2 in soil pore spaces and the flux of CO2 from soils to the atmosphere. Key discoveries from this work were that hydrologic export of dissolved inorganic carbon (Hodges et al. 2021), and iron redox reactions (Hodges et al. 2023) are significant controls on soil CO2. These processes vary topographically, and as the region experiences more intense precipitation events, CO2 efflux may increase on ridges and decline at the valley floor within the same watershed (Kopp et al. 2022).
Our soil CO2 measurements are often used in collaboration with other Critical Zone scientists in the areas of weathering, model development, and microbial ecology. We have studied how CO2 affects weathering rates, which has led to studies of root activity in shale fractures (Hasenmueller et al. 2017), and the role of weathering in controlling phosphorus availability in soils developed over shale vs sandstone (Marcon et al. 2021). Our field measurements have been coupled with ecosystem models of forest carbon dynamics (Smeglin et al. 2020), “Earthcasting” models of future weathering (Sullivan et al. 2019), and reactive transport models (Zhi et al. 2019). In manipulative experiments (McDaniel et al. 2013) and cross site studies (Dove et al. 2020; Brewer et al. 2019) we have examined changes in microbial communities and production of enzymes that break down soil organic matter. The rapid growth of this field led us to review how forest management planning could increase use of Critical Zone science in different regions of the US (Kopp et al. 2023).
Forthcoming research in this area examines factors that control diel patterns in soil CO2 efflux, and the role of metal cations in controlling soil carbon storage.
The Kaye Biogeochemistry Lab believes that everyone should have equal access to science, and we strive to create an environment that welcomes and respects diversity in all its forms—including cultural, racial, religious, age, gender identity, sexual orientation, physical ability, and mental wellbeing. Read more here.
The Kaye Biogeochemistry Lab believes that everyone should have equal access to science, and we strive to create an environment that welcomes and respects diversity in all its forms—including cultural, racial, religious, age, gender identity, sexual orientation, physical ability, and mental wellbeing. Read more here.
