Dissecting soil CO2 fluxes from a subtropical forest in China by integrating field measurements with a modeling approach

Terrestrial carbon sequestration involves a series of processes, including photosynthesis, plant autotrophic respiration and soil microbial heterotrophic respiration. Field measurements of carbon dioxide (CO2) using either eddy covariance or chamber methods usually provide bulk CO2 fluxes from more than one sink or source. For the purpose of estimating the C budget in ecosystems, it is inherently important to determine the individual sinks or sources. This report describes how we tested the Forest-DNDC model using a dataset collected at a subtropical forest site in Sichuan Province, China. One-year field measurements were conducted using a chamber method at four plots with different treatments that were specifically designed to distinguish the CO2 fluxes produced from three sources: root respiration, forest floor respiration and mineral soil respiration. The obtained datasets were utilized to verify the modeled CO2 fluxes from the corresponding sources for the tested forest ecosystem. Results from the tests indicated that Forest-DNDC was capable not only of quantifying the total CO2 emissions but also of distinguishing their sources related to plant autotrophic and soil microbial heterotrophic respiration. Because measuring root respiration is always difficult in field investigations, adopting Forest-DNDC for quantifying root respiration represents an appropriate complement to most field measurements.