Atmospheric N Deposition Significantly Enhanced Soil N<sub>2</sub>O Emission From Eastern China Forests
Xiaoyu Cen, Mingxu Li, Li Xu, Jianxing Zhu, Nianpeng He
Abstract
Abstract Nitrous oxide (N 2 O) is an influential greenhouse gas (GHG) and an unregulated ozone‐depleting substance. The extent to which N 2 O emissions from natural forest soils have been enhanced by high atmospheric nitrogen (N) deposition in China during past decades is unclear; however, assessing land‐related N 2 O emissions for 2060 national “carbon neutrality” goal is urgent. In this study, we proposed a “gray box” conceptual model and deduced a linear relationship between soil N 2 O emissions and N deposition on a large scale. On this basis, we created a “process‐augmented data‐driven” approach using which we combined experimental N addition data from 38 Chinese forests with N deposition observation data to estimate regional soil N 2 O emissions. We found that the N 2 O emission budget of eastern China forest soils averaged 0.24 ± 0.07 TgN yr −1 from 1996 to 2015; of this, ∼36% (0.087 TgN yr −1 ) was directly induced by N deposition. Soil N 2 O emission rates ( R N2O ) fluctuated slightly after 2006, and the R N2O s of different ecoregions were significantly different ( p < 0.001). Soil factors and N‐deposition‐related factors dominated the spatial variation of R N2O . Our findings provide country‐specific and ecoregion‐specific emission factors for national GHG inventories in China. Our approach bridges the gap between site‐level experiments and demand for regional N 2 O emissions, and is applicable for estimating N 2 O emissions in other countries/regions. Meanwhile, more N addition experiments are needed to comprehensively understand N cycling processes and extend the predictive capability of the approach.