Fine-scale microclimatic controls on soil carbon dioxide fluxes in a northern hardwood forest

Carbon dioxide (CO2) emissions from soil are typically the largest carbon flux from forest ecosystems to the atmosphere, representing a significant biogenic source of greenhouse gases. Although the temperature and moisture sensitivities of the respiration processes underlying soil CO2 fluxes are well studied, the impacts of a changing climate on these abiotic controls and the resulting soil flux responses are unresolved. Using in-situ continuous measurements of soil microclimate at sites with contrasting hydrology, this study assessed the temperature and moisture dependence of soil CO2 fluxes within hardwood forests of the Adirondack Mountains in northern New York State (USA). During the 2018 growing season, soil CO2 fluxes were very strongly coupled with soil temperature and only weakly coupled with soil moisture. Statistical modeling indicated that the relationship between soil moisture and the CO2 flux was driven by their covariation with soil temperature. Moderate drought conditions during the 2018 growing season affirmed the importance of soil moisture regimes in mediating weather variability, yet there was limited evidence to indicate that respiration was significantly moisture-limited