Responses of CH 4 and N 2 O fluxes to land-use conversion and fertilization in a typical red soil region of southern China

Land-use conversion and fertilization have been widely reported as important management practices affecting CH 4 and N 2 O fluxes; however, few long-term in situ measurements are available after land-use conversion from rice paddies to upland cultivation, especially those including the initial stages after conversion. A 3-year field experiment was conducted in rice paddies and a newly converted citrus orchard to measure CH 4 and N 2 O fluxes in response to land-use conversion and fertilization in a red soil region of southern China. Annual CH 4 and N 2 O emissions averaged 303.9 kg C ha −1 and 3.8 kg N ha −1 , respectively, for the rice paddies over three cultivation years. Although annual N 2 O emissions increased two- to threefold after the conversion of rice paddies to citrus orchard, the substantial reduction in CH 4 emissions and even shift into a sink for atmospheric CH 4 led to significantly lower CO 2 -eq emissions of CH 4 and N 2 O in the citrus orchard compared to the rice paddies. Moreover, distinct CH 4 emissions were observed during the initial stages and sustained for several weeks after conversion. Our results indicated that the conversion of rice paddies to citrus orchards in this region for higher economic benefits may also lead to lower aggregate CH 4 and N 2 O emissions.