Thinning intensity but not replanting different species affects soil N2O and CH4 fluxes in Cunninghamia lanceolata plantation

Thinning and replanting are effective forest management measures to improve the stand structure and species composition of artificial forests. However, the effects of thinning and replanting on soil N2O and CH4 fluxes and their associations with changes in soil environment factors have been poorly understood in plantation forests. A 36-month field experiment was conducted to elucidate the effects of thinning and replanting different species on soil N2O and CH4 fluxes and related environmental factors in Cunninghamia lanceolata plantation on shallow soil. The experiment consisted of five treatments, uncut control (CK), moderate thinning + replanting evergreen seedlings (MTE), moderate thinning + replanting deciduous seedlings (MTD), heavy thinning + replanting evergreen seedlings (HTE), heavy thinning + replanting deciduous seedlings (HTD). Compared with the control, moderate and heavy thinning increased cumulative N2O emissions by 12.4% and 21.4%, respectively, and reduced CH4 cumulative uptake by 35.4% and 38.8%, respectively. However, the effects on soil N2O and CH4 fluxes replanting deciduous or evergreen seedlings were insignificant. The results showed that thinning increased N2O emissions and decreased CH4 uptake due to the increased soil temperature, labile C and N concentrations. Soil temperature was the dominant factor, and mineral N was a contributing factor affecting N2O and CH4 fluxes. The study concludes that thinning increased the global warming potential with N2O contributing more than CH4 (113.5%: -13.5%). Our findings highlight that thinning increased N2O emissions and decreased CH4 uptake with the increasing intensity and the replanting had no different effects between deciduous and evergreen seedlings on the fluxes of N2O and CH4 during the early years following thinning.