2024 Abstracts

Ecohydrological Controls on Root and Microbial Respiration in the East River Watershed of Colorado


Austin Simonpietri* (ats327@nau.edu), Mariah Carbone, Andrew Richardson


Northern Arizona University, Flagstaff, AZ



Mountainous ecosystems in the western United States are experiencing substantial changes in their water inputs with the dominant water source—snowpack—decreasing and melting earlier, and monsoon rains becoming more sporadic. In these ecosystems, there is a lack of understanding of how belowground soil carbon production (CO2 flux) will respond to these changes in precipitation inputs. This is in part due to the logistical difficulty of conducting fieldwork in these ecosystems’ complex terrain, as well as the technical challenge of separating the two components of the CO2 flux, root, and microbial respiration. This research aims to understand how precipitation inputs influence root and microbial respiration individually by conducting an intensive radiocarbon sampling campaign paired with long-term continuous measurements of the CO2 flux and its primary environmental and biological drivers (soil temperature, soil water content, and plant productivity). During the summer of 2022, the team conducted four different field visits over 24 days at long-term environmental monitoring sites in the East River Watershed of Colorado. Samples collected included manual CO2 flux, soil water content, and soil temperature. These measurements were used to constrain and validate the continuously measured CO2 flux at these sites. During the July-September sampling, Simonpietri collected more than 150 radiocarbon samples to separate root from microbial respiration through isotopic partitioning. Simonpietri processed each of these samples (1 hr sample-1) by purifying them to CO2, then graphitizing and pressing them into aluminum capsules to be run on the accelerator mass spectrometer. The primary findings from this research show that root and microbial respiration have different environmental sensitivities throughout the growing season.