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（ecosystem carbon, C）动态的影响存在高度异质性，其潜在作用机制仍未明晰。在此，我们提出一套全新的概念框架，整合植物、微生物与地球化学机制，以调和氮素对土壤碳的多样且相悖的影响。本研究依托蒙古草原（Mongolian steppe grassland）开展的长期氮素富集与酸添加实验对该框架进行了验证。不同的机制可分别阐释氮素对颗粒态与矿物结合态土壤碳库的影响，这或可解释过往诸多氮添加研究间的分歧。尽管植物生产主导了颗粒态碳库的变化，但氮素诱导的土壤酸化通过抑制微生物生长，以及铁铝矿物与碳之间的pH敏感结合过程，对矿物结合态碳库产生了强烈影响。我们的研究结果表明，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（Earth system models）中，应纳入氮素诱导的酸化对微生物呼吸与地球化学性质的影响。