State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
College of Resources and Environmental Sciences, Key Laboratory of Farmland Eco-Environment of Hebei, Hebei Agricultural University, Baoding, China.
Glob Chang Biol. 2023 Jul;29(13):3591-3600. doi: 10.1111/gcb.16716. Epub 2023 Apr 21.
Soil respiration (Rs), as the second largest flux of carbon dioxide (CO ) between terrestrial ecosystems and the atmosphere, is vulnerable to global nitrogen (N) enrichment. However, the global distribution of the N effects on Rs remains uncertain. Here, we compiled a new database containing 1282 observations of Rs and its heterotrophic component (Rh) in field N manipulative experiments from 317 published papers. Using this up-to-date database, we first performed a formal meta-analysis to explore the responses of Rs and Rh to N addition, and then presented a global spatially explicit quantification of the N effects using a Random Forest model. Our results showed that experimental N addition significantly increased Rs but had a minimal impact on Rh, not supporting the prevailing view that N enrichment inhibits soil microbial respiration. For the major biomes, the magnitude of N input was the main determinant of the spatial variation in Rs response, while the most important predictors for Rh response were biome specific. Based on the key predictors, global mapping visually demonstrated a positive N effect in the regions with higher anthropogenic N inputs (i.e., atmospheric N deposition and agricultural fertilization). Overall, our analysis not only provides novel insight into the N effects on soil CO fluxes, but also presents a spatially explicit assessment of the N effects at the global scale, which are pivotal for understanding ecosystem carbon dynamics in future scenarios with more frequent anthropogenic activities.
土壤呼吸（Rs）作为陆地生态系统与大气之间二氧化碳（CO）的第二大通量，易受到全球氮（N）富集的影响。然而，全球范围内 N 对 Rs 的影响分布仍不确定。在这里，我们编译了一个新的数据库，其中包含 317 篇已发表论文中 1282 个关于 Rs 及其异养组分（Rh）的野外 N 管理实验的观测值。利用这个最新的数据库，我们首先进行了正式的荟萃分析，以探讨 Rs 和 Rh 对 N 添加的响应，然后使用随机森林模型呈现了全球空间显式量化的 N 影响。结果表明，实验性 N 添加显著增加了 Rs，但对 Rh 的影响最小，这与 N 富集抑制土壤微生物呼吸的普遍观点不一致。对于主要的生物群落，N 输入的幅度是 Rs 响应空间变化的主要决定因素，而 Rh 响应的最重要预测因子则是生物群落特有的。基于关键预测因子，全球映射直观地显示了在具有较高人为 N 输入（即大气 N 沉降和农业施肥）的区域存在正向 N 效应。总的来说，我们的分析不仅为 N 对土壤 CO 通量的影响提供了新的见解，还对全球范围内的 N 影响进行了空间显式评估，这对于理解未来人为活动更频繁的情景下生态系统碳动态至关重要。
