Drivers of soil carbon persistence in dryland floodplains: Constraining the feedbacks among hydrology, mineral stabilization, and respiration

River floodplains play a fundamental role in regulating the movement and storage of carbon within Earth's surface, influencing soil development, water quality, ecosystem productivity, and long-term landscape evolution. Floodplains can store carbon in soils for hundreds to thousands of years, but they can also release carbon back to the environment as conditions change. This project will investigate how changing water levels, flooding, and soil conditions determine whether floodplains in semi-arid regions, such as the Southwestern United States, store carbon or release it. The project will also support science education through a K-12 citizen science program and interdisciplinary research training for students. The research team will combine field measurements of groundwater depth and greenhouse gas emissions with laboratory analyses of the age and composition of carbon stored in floodplain sediments. These data will be used to develop a mechanistic framework linking hydrology, secondary mineral formation, and carbon cycling in semi-arid floodplains. Leveraging a network of long-term monitoring sites along the Rio Grande, the project will determine how spatial and temporal variations in flooding, groundwater depth, and soil conditions control carbon storage and release across the floodplain. Results will advance fundamental understanding of carbon cycling at the interface of hydrologic, geomorphic, and biogeochemical processes, improve representation of river corridors in Earth system models, and provide new insights into the functioning and resilience of river corridor ecosystems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.