Using a modified DNDC model to estimate N 2O fluxes from semi-arid grassland in China

Abstract

Field measurement results showed that approximately 40% of the annual N 2O losses occurred during the non-growing season and confirmed the importance of spring and autumn periods for assessment of total N 2O losses from semi-arid temperate grassland in China. In the previous study, we found that the 7.2 version of Denitrification–Decomposition (DNDC) model had significantly lower estimates of N 2O losses in spring and autumn time. In this study, three modifications, which mainly focus on the nitrification sub-model, the impact of soil frost and snow cover on gas production and emission, had been made to the model code. Based on field measurement, we concluded that modified version of DNDC model is more suitable for estimating the magnitude and seasonal trends of N 2O losses from this region on a plot scale. By extrapolating the field data with our modified model, we estimated that the annual N 2O emission rates for natural temperate grasslands of northern China is ca. 0.056 T g N 2O–N y −1, i.e. ca. 40% lower than the estimate based only on field measurements (ca. 0.092 T g N 2O–N y −1).