Global chronic nitrogen (N) deposition to forests can alleviate ecosystem N limitation, with potentially wide ranging consequences for biodiversity, carbon sequestration, soil and surface water quality, and greenhouse gas emissions. However, the ability to predict these consequences requires improved quantification of hard-to-measure N fluxes, particularly N gas loss and soil N retention. Here we combine a unique set of long-term catchment N budgets in the central Europe with ecosystem ¹⁵N data to reveal fundamental controls over dissolved and gaseous N fluxes in temperate forests. Stream leaching losses of dissolved N corresponded with nutrient stoichiometry of the forest floor, with stream N losses increasing as ecosystems progress towards phosphorus limitation, while soil N storage increased with oxalate extractable iron and aluminium content. Our estimates of soil gaseous losses based on ¹⁵N stocks averaged 2.5 2.2 kg N ha⁻¹ yr⁻¹ and comprised 20% 14% of total N deposition. Gaseous N losses increased with forest floor N:P ratio and with dissolved N losses. Our relationship between gaseous and dissolved N losses was also able to explain previous ¹⁵N-based N loss rates measured in tropical and subtropical catchments, suggesting a generalisable response driven by nitrate (NO₃ ⁻) abundance and in which the relative importance of dissolved N over gaseous N losses tended to increase with increasing NO₃ ⁻ export. Applying this relationship globally, we extrapolated current gaseous N loss flux from forests to be 8.9 Tg N yr⁻¹, which represent 39% of current N deposition to forests worldwide.

全球森林中的慢性氮 (N) 沉积可以缓解生态系统氮的限制，对生物多样性、碳固存、土壤和地表水质量以及温室气体排放产生潜在的广泛影响。然而，预测这些后果的能力需要改进难以测量的 N 通量的量化，特别是 N 气体损失和土壤 N 保留。在这里，我们将中欧一组独特的长期集水区 N 预算与生态系统^{15 结合起来}N 数据揭示了对温带森林中溶解和气态 N 通量的基本控制。溶解 N 的河流浸出损失与森林地面的养分化学计量相对应，随着生态系统向磷限制发展，河流 N 损失增加，而土壤 N 储存量随着草酸盐可提取铁和铝含量的增加而增加。我们基于^{15 个}N 库对土壤气态损失的估计平均为 2.5 2.2 kg N ha ^-1 yr ^-1，占总氮沉积的 20% 14%。气态氮损失随着森林地面氮磷比和溶解氮损失而增加。我们的气态氮损失和溶解氮损失之间的关系也能够解释之前的¹⁵在热带和亚热带集水区测量的基于 N 的 N 损失率，表明由硝酸盐 (NO ₃ ^- ) 丰度驱动的普遍响应，其中溶解 N 相对于气态 N 损失的相对重要性随着 NO ₃ ^-出口的增加而增加。在全球范围内应用这种关系，我们推断当前来自森林的气态氮损失通量为 8.9 Tg N yr ^-1，这代表了当前全球森林氮沉积的 39%。