| 摘 要： |
Nitrous oxide (N2O) is an influential greenhouse gas (GHG) and an unregulated ozone-depleting substance. The extent to which N2O 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 N2O 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 N2O 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 N2O emissions. We found that the N2O emission budget of eastern China forest soils averaged 0.24 +/- 0.07 TgN yr(-1) from 1996 to 2015; of this, similar to 36% (0.087 TgN yr(-1)) was directly induced by N deposition. Soil N2O 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 N2O emissions, and is applicable for estimating N2O 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. |
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