Long-term(42 years) effect of thinning on soil CO2 emission in a mixed broadleaved-Korean pine(Pinus koraiensis) forest in Northeast China

Thinning is an important forest management practice that has great potential to influence regional soil carbon storage and dynamics. The present study measured soil respiration(RS, the efflux of CO2 emitted) and its two components(heterotrophic(RH) and autotrophic(RA) respiration) from soil 42 years after thinning in comparison to un-thinning(control). Autotrophic respiration was significantly greater in the thinning plot, approximately 44% higher compared to the control, while both RSand RHwere slightly, but not significantly, higher in the thinning plot. Higher fine root biomass might have contributed to the higher RAin the thinning plot. Both RSand RHshowed clear soil temperature-dependent seasonal patterns, whereas RAwas less responsive to changes in temperature, especially within one specific season. The annual and season-specific temperature sensitivities of RSand RHwere lower in the thinning plot,specifically during the mid-growing season. Furthermore, variations in the season-specific temperature sensitivity of RSand RHwere less intense in the thinning plot. We conclude that forest thinning can reduce the temperature sensitivity of RSand RHduring the mid-growing season and increase soil CO2 emission in the long term.