Responses of CO2, N2O and CH4 fluxes between atmosphere and forest soil to changes in multiple environmental conditions

To investigate the effects of multiple environmental conditions on greenhouse gas (CO2, N2O, CH4) fluxes, we transferred three soil monoliths from Masson pine forest (PF) or coniferous and broadleaved mixed forest (MF) at Jigongshan to corresponding forest type at Dinghushan. Greenhouse gas fluxes at the in situ (Jigongshan), transported and ambient (Dinghushan) soil monoliths were measured using static chambers. When the transported soil monoliths experienced the external environmental factors (temperature, precipitation and nitrogen deposition) at Dinghushan, its annual soil CO2 emissions were 54% in PF and 60% in MF higher than those from the respective in situ treatment. Annual soil N2O emissions were 45% in PF and 44% in MF higher than those from the respective in situ treatment. There were no significant differences in annual soil CO2 or N2O emissions between the transported and ambient treatments. However, annual CH4 uptake by the transported soil monoliths in PF or MF was not significantly different from that at the respective in situ treatment, and was significantly lower than that at the respective ambient treatment. Therefore, external environmental factors were the major drivers of soil CO2 and N2O emissions, while soil was the dominant controller of soil CH4 uptake. We further tested the results by developing simple empirical models using the observed fluxes of CO2 and N2O from the in situ treatment and found that the empirical models can explain about 90% for CO2 and 40% for N2O of the observed variations at the transported treatment. Results from this study suggest that the different responses of soil CO2, N2O, CH4 fluxes to changes in multiple environmental conditions need to be considered in global change study.