DataSheet_1_Global variations and drivers of nitrous oxide emissions from forests and grasslands.docx

Nitrous oxide (N2O) emissions are highly variable due to the complex interaction of climatic and ecological factors. Here, we obtained in-situ annual N2O emission flux data from almost 180 peer-papers to evaluate the dominant drivers of N2O emissions from forests and unfertilized grasslands at a global scale. The average value of N2O emission fluxes from forest (1.389 kg Nha-1yr-1) is almost twice as large as that from grassland (0.675 kg Nha-1yr-1). Soil texture and climate are the primary drivers of global forest and grassland annual N2O emissions. However, the best predictors varied according to land use and region. Soil clay content was the best predictor for N2O emissions from forest soils, especially in moist or wet regions, while soil sand content predicted N2O emissions from dry or moist grasslands in temperate and tropical regions best. Air temperature was important for N2O emission from forest, while precipitation was more efficient in grassland. This study provides an overall understanding of the relationship between natural N2O emissions and climatic and environmental variables. Moreover, the identification of principle factors for different regions will reduce the uncertainty range of N2O flux estimates, and help to identify region specific climate change mitigation and adaptation strategies.

氧化亚氮（Nitrous oxide, N₂O）排放受气候与生态因子的复杂交互作用影响，具有高度变异性。本研究收集了近180篇同行评议论文中的原位年N₂O排放通量数据，以全球尺度解析森林与未施肥草地N₂O排放的主导驱动因子。研究结果表明，森林N₂O排放通量的平均值为1.389 kg N·ha⁻¹·yr⁻¹，几乎是草地（0.675 kg N·ha⁻¹·yr⁻¹）的两倍。土壤质地与气候是全球森林及未施肥草地年N₂O排放的核心驱动因子，但最优预测因子会因土地利用类型与区域差异而有所不同。森林土壤N₂O排放的最优预测因子为土壤黏粒含量，在湿润或高湿区域尤为显著；而温带与热带区域内干旱或湿润草地的N₂O排放，则以土壤砂粒含量作为最优预测因子效果最佳。气温对森林N₂O排放的影响更为显著，而降水则对草地N₂O排放的调控作用更强。本研究全面阐明了自然源N₂O排放与气候、环境变量之间的关联机制。此外，明确不同区域的主控因子，可缩小N₂O通量估算的不确定性区间，有助于制定针对特定区域的气候变化减缓与适应策略。