Ecohydrological Controls on Root and Microbial Respiration in the East River Watershed of Colorado
Authors
Austin Simonpietri*, Andrew Richardson, Mariah Carbone (ats327@nau.edu)
Institutions
Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ
URLs
Abstract
Researchers seek to understand how moisture inputs, such as snow and rain, influence the amount of carbon dioxide (CO2) produced by microbial and root respiration in the East River Watershed near Crested Butte, CO. In 2021, a team instrumented four sites along Snodgrass Mountain in the two main forest types, aspen and conifer. To date, researchers have half-hourly continuous measurements of the flux of CO2 from the soil to the atmosphere and its primary environmental and biological drivers. During the growing season (July to September; GS) of 2022, the team collected radiocarbon samples to separate the root and microbial respiration contributions to the soil CO2 flux. The 2022 GS had near 30-year normal precipitation inputs, with 570 mm of water (H2O) falling as snow in the preceding winter, and 248 mm H2O from the summer rains. The conifer soils were wetter and cooler compared to the aspen soils. These differences were strongly mediated by the canopy structure of the forest types. On average, the conifer forests had a higher seasonal soil CO2 flux (583.3 ± 127 g C m-2 GS-1) and greater seasonal microbial contribution (57 ± 15%) than the aspen forests (476 ± 123 g C m-2 GS-1 and 44 ± 7%). The seasonal pattern of root and microbial respiration was similar between forest types. Microbial respiration peaked in July and August following monsoon rains, ranging between 1.7 to 4.0 µmol CO2 m-2 s-1. Root respiration was greatest in September, when soils were driest, ranging between 1.4 to 3.5 µmol CO2 m-2 s-1.
Microbial respiration was strongly temperature sensitive in July and August, but showed H2O limitation in both forest types in September. Aspen-root respiration had a stronger temperature sensitivity than conifer-root respiration throughout the GS. The results provide insight into how belowground processes may be influenced by changing moisture inputs in these montane ecosystems.