黑土不同土地利用方式下受水分有效性调节的土壤CO2排放的温度敏感性

The quantification of soil CO2 efflux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO2 depending upon land use.This study investigated responses of soil CO2 efflux variability to soil temperature interactions with diferent soil moisture levels under various land use types including grassland,bare land,and arable(maize,soybean,and wheat)land in the black soil zone of Northeast China.The soil CO2 effluxes with and without live roots,defined as the total CO2 efflux(FtS)and the root-free CO2 efflux(FrfS),respectively,were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography.The seasonal soil CO2 fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards.The mean seasonal FtS ranged from 20.3±7.8 to 58.1±21.3 mg CO2-C m-2h-1 for all land use types and decreased in the order of soybean land>grassland>maize land>wheat land>bare land,while the corresponding values of FrfS were relatively lower,ranging from 20.3±7.8 to 42.3±21.3 mg CO2-C m-2h-1.The annual cumulative FtS was in the range of 107-315 g CO2-C m-2 across all land uses types.The seasonal CO2 effluxes were significantly(P<0.001)sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO2 efflux variability.Correspondingly,the temperature coefcient Q10 values varied from 2.1 to 4.5 for the seasonal FtS and 2.2 to 3.9 for the FrfS during the growing season.Soil temperature interacting with soil moisture accounted for a significant fraction of the CO2 flux variability for FtS (up to 61%) and FrfS (up to 67%) via a well-defined multiple regression model,indicating that temperature sensitivity of CO2 flux can be mediated by water availability,especially under water stress.

Temporal variations in soil CO2 efflux under different land use types in the black soil zone of Northeast China

The quantification of soil CO₂ efflux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO₂ depending upon land use. This study investigated responses of soil CO₂ efflux variability to soil temperature interactions with different soil moisture levels under various land use types including grassland, bare land, and arable (maize, soybean, and wheat) land in the black soil zone of Northeast China. The soil CO₂ effluxes with and without live roots, defined as the total CO₂ efflux (F_tS) and the root-free CO₂ efflux (F_rfS), respectively, were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography. The seasonal soil CO₂ fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards. The mean seasonal F_tS ranged from 20.3±7.8 to 58.1±21.3 mg CO₂-C m^-2 h^-1 for all land use types and decreased in the order of soybean land > grassland > maize land > wheat land > bare land, while the corresponding values of F_rfS were relatively lower, ranging from 20.3±7.8 to 42.3±21.3 mg CO₂-C m^-2 h^-1. The annual cumulative FtS was in the range of 107--315 g CO₂-C m^-2 across all land use types. The seasonal CO₂ effluxes were significantly (P < 0.001) sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO₂ efflux variability. Correspondingly, the temperature coefficient Q₁₀ values varied from 2.1 to 4.5 for the seasonal F_tS and 2.2 to 3.9 for the F_rfS during the growing season. Soil temperature interacting with soil moisture accounted for a significant fraction of the CO₂ flux variability for F_tS (up to 61%) and F_rfS (up to 67%) via a well-defined multiple regression model, indicating that temperature sensitivity of CO₂ flux can be mediated by water availability, especially under water stress.