Soil respiration in a subtropical forest of southwestern China: Components, patterns and controls

Partitioning the components of soil respiration is crucial to understand and model carbon cycling in forest ecosystems. In this study, total soil respiration (RS), autotrophic respiration (RA), heterotrophic respiration (RH), litter respiration (RL), litterfall input and environmental factors were synchronously monitored for 2 years in a subtropical Michelia wilsonii forest of southwestern China. RH rates were often higher than RA rates during the two years except for the middle growing season (from July to September). The mean rate of Rs, RA, RH and RL was 1.94 μmol m-1 s-1, 0.85 μmol m-1 s-1, 1.09 μmol m-1 s-1 and 0.65 μmol m-1 s-1, respectively, during the 2-year experiment. Annual CO2 emission derived from RA, RH and RL was 3.26 Mg C ha-1 a-1, 4.67 Mg C ha-1 a-1 and 2.61 Mg C ha-1 a-1, respectively, which accounted for 41.4%, 58.6% and 32.9% of RS. Over the experimental period, the ratio of RA/RS increased with soil temperature but the opposite was true for RH/RS and RL/RS. The Q10 value was 2.01, 4.01, 1.34 and 1.30, respectively, for RS, RA, RH and RL. Path analysis indicated that environmental variables and litterfall production together explained 82.0%, 86.8%, 42.9% and 34.7% variations of monthly fluxes of RS, RA, RH and RL, respectively. Taken together, our results highlight the differential responses of the components of RS to environmental variables.