Seasonal Variation of Emission Fluxes of CO2, CH4, and N2O from Different Larch Forests in the Daxing'An Mountains of China

Using a static chamber-gas chromatography method, we investigate the characteristics of soil CO2, CH4, and N2O fluxes and their relationships with environmental factors during the growing season in four typical Larix gmelinii forests (moss-Larix gmelinii forest, Ledum palustre-Larix gmelinii forest, herbage-Larix gmelinii forest, and Rhododendron dauricum-Larix gmelinii forest) in the Greater Khingan Mountains. Our results show that all four forest types are sources of CO2 emissions, with similar average emission fluxes (146.71 mg & BULL;m(-2) h(-1)-211.81 mg & BULL;m(-2) h(-1)) and no significant differences. The soil in the moss-Larix gmelinii forest emitted CH4 (43.78 & mu;g & BULL;m(-2) h(-1)), while all other forest types acted as CH4 sinks (-56.02 & mu;g & BULL;m(-2) h(-1)--28.07 & mu;g & BULL;m(-2) h(-1)). Although all forest types showed N2O uptake at the beginning of the growing season, the N2O fluxes (4.03 & mu;g & BULL;m(-2) h(-1)-5.74 & mu;g & BULL;m(-2) h(-1)) did not differ significantly among the four forest types for the entire growing season, and all acted as sources of N2O emissions. The fluxes of CO2, CH4, and N2O were significantly correlated with soil temperature and soil pH for all four forest types. Multiple regression analysis shows that considering the interactive effects of soil temperature and moisture could better explain the changes in greenhouse gas emissions among different forest types. The average Q(10) value (8.81) of the moss-Larix gmelinii forest is significantly higher than that of the other three forest types (3.16-3.54) (p < 0.05), indicating that the soil respiration in this forest type is more sensitive to temperature changes.