Effects of wildfire on soil respiration and its heterotrophic and autotrophic components in a montane coniferous forest

Aims Episodic wildfires are expected to occur more frequently under future climate change scenarios, with substantial effects on CO2 exchange between terrestrial ecosystems and the atmosphere. This study examined the effects of wildfire on soil respiration (R-S) and its heterotrophic (R-H) and autotrophic (R-A) components, as well as their temperature responses (temperature sensitivity, Q(10)). Methods We began this study in January 2014, 8 months after a wildfire, in a montane coniferous forest in southwestern China. A trenching method was used to exclude plant roots and quantify R-H. R-A was calculated by subtracting R-H from R-S. Important findings From 2014 to 2015, the wildfire significantly reduced R-S, R-H and R-A by 61.3%, 42.5% and 84.0%, respectively, leading to increases in the ratio of R-H to R-S, from 0.63 in the unburned stand to 0.85 in the burned stand. Ignoring diurnal differences, the wildfire did not affect the Q(10) of R-S or R-H, but substantially decreased the Q(10) of R-A, from 2.62 in the unburned stand to 2.08 in the burned stand. However, the daytime Q(10) of R-S and R-H was suppressed following the wildfire by 25.1% and 28.8%, respectively, primarily due to increased daytime soil temperature. In the montane coniferous forest, monthly precipitation but not soil temperature drove seasonal dynamics of soil CO2 release. Our findings help to clarify the mechanisms underlying carbon cycling responses to natural disturbance, especially under a warmer future climate.