Data from: Reconciling multiple impacts of nitrogen enrichment on soil carbon: plant, microbial, and geochemical controls

Impacts of reactive nitrogen (N) inputs on ecosystem carbon (C) dynamics are highly variable, and the underlying mechanisms remain unclear. Here, we proposed a new conceptual framework that integrates plant, microbial, and geochemical mechanisms to reconcile diverse and contrasting impacts of N on soil C. This framework was tested using long-term N enrichment and acid addition experiments in a Mongolian steppe grassland. Distinct mechanisms could explain effects of N on particulate and mineral-associated soil C pools, potentially explaining discrepancies among previous N addition studies. While plant production predominated particulate C changes, N-induced soil acidification strongly affected mineral-associated C through decreased microbial growth and pH-sensitive associations between iron and aluminum minerals and C. Our findings suggest that effects of N-induced acidification on microbial respiration and geochemical properties should be included in Earth system models that predict ecosystem C budgets under future N deposition/input scenarios.

活性氮（reactive nitrogen, N）输入对生态系统碳（carbon, C）动态的影响存在高度变异性，其内在作用机制仍不明确。本研究提出一套整合植物、微生物与地球化学机制的全新概念框架，以协调氮素对土壤碳的多样且相悖的影响效应。该框架依托蒙古草原草地的长期氮富集与酸添加实验完成验证。不同的作用机制可分别解释氮素对颗粒态与矿物结合态土壤碳库的影响，这或可阐释此前氮添加研究间的结论差异。植物生产主导了颗粒态碳的变化，而氮诱导的土壤酸化则通过降低微生物生长以及铁铝矿物与碳之间的pH敏感结合作用，显著影响矿物结合态碳。本研究结果表明，在预测未来氮沉降/输入情景下生态系统碳预算的地球系统模型中，应纳入氮诱导的土壤酸化对微生物呼吸与地球化学性质的影响效应。