Clear-cutting and slash burning effects on soil CO2 efflux partitioning in Chinese fir and evergreen broadleaved forests in subtropical China

Clear-cutting (CC) and slash burning (SB) are common silvicultural practices in subtropical China, yet the time-course response of soil CO2 efflux components to such disturbance is not well understood. This study examined the effects of CC and SB on soil CO2 efflux components in a Cunninghamia lanceolata (Lamb.) Hook (Chinese fir, CF) plantation and a secondary evergreen broadleaved forest (BF) located in Fujian Province, southeastern China. Aboveground litter removal and root trenching were used to estimate CO2 fluxes from soil organic matter decomposition (R-SOM), litter decomposition (R-L), and autotrophic respiration by roots and mycorrhizae (R-R). These components were measured 5-7 times per month from 18 October 2001 to 25 December 2003 using soda lime absorption. We found that R-R, R-L and R-SOM were initially higher in CC and SB plots than controls in both forests, but these three component fluxes in disturbed plots all fell below those of the control 5-20 months after the disturbance. Also, Q(10) values of these components decreased following disturbance. The annual flux of each respiration component was greater under BF than CF. The contribution of R-R to soil CO2 efflux in the control plots averaged 35% in CF and 46% in BF. R-SOM was the dominant component of soil CO2 efflux in CC and SB plots, accounting for over 50%. Our results highlight the importance of temporal trends of the component fluxes following disturbance and contribute to a broader understanding of forest management effects on the soil C cycle.