Research On Soil Greenhouse Gas Emissions In Pure And Mixed Stands Of Chinese Fir

To investigate the differences in soil CO2,N2O and CH4 emissions as well as CO2,N2O and CH4 emission factors from Chinese fir?Cunninghamia lanceolata?stands?CL?and mixed stands of Chinese fir and Cinnamomum camphora?CL-CC?,Castanopsis fargesii?CL-CF?,and Alnus cremastogyne?CL-AC?in Huitong county,Hunan province,CO2,N2O and CH4 emissions were observed and quantified with a static chamber-gas chromatography method and laboratory incubations of mineral soil.The objectives of the study were to assess the effects of tree species composition on soil greenhouse gases and to investigate their controlling factors providing a scientific basis for suitable species composition in mixed stands to realize carbon sequestration potential.The results showed:?1?CO₂ emissions in CL(490.48 mg·m^-2·h^-1)and in CL-CC(487.92±40.62mg·m^-2·h^-1)were significantly higher than in CL-CF(254.27 mg·m^-2·h^-1)and CL-AC(331.51 mg·m^-2·h^-1).?2?Average N2O emissions in CL-CC,CL-CF,CL-AC and CL were 0.0260±0.0143,0.0027±0.0133,0.0323±0.0153 and 0.0322±0.0125mg·m^-2·h^-1,respectively.N2O emissions in CL-AC and CL were significantly higher than in CL-CF.?3?There were no significant differences in CH4 emissions of the 4 stands.Average CH4emissions in CL-CC,CL-CF,CL-AC and CL were-0.0264±0.0036,-0.0314±0.0032,-0.0230±0.0036 and-0.0220±0.0035mg·m^-2·h^-1,respectively.?4?In CL-CF,CL-AC,and CL,a linear relationship was observed between CO2 and soil temperature?R²=0.25,0.29,0.25,respectively?.In CL-CF,CL-AC,and CL,an exponential relationship was observed between N2O emissions and WFPS?R²=0.61,0.96,0.71,respectively?.CH4 emissions were not significantly affected by soil temperature and WFPS in all 4 stands.Also,nitrate-N were significantly correlated with soil N2O emissions.Differences in soil greenhouse gases emissions among the stands possibly being attributed to differences in soil NO3^--N content and soil N mineralization rate.