The effects of nitrogen (N) deposition on forests largely depend on the ecosystem N status and the fates of deposited N. Boreal forests are typically N-limited ecosystems and are considered to be more efficient in retaining deposited N relative to temperate and tropical forests. As a primary disturbance in boreal forests, wildfires may alleviate N limitation in the burned ecosystem and increase mineralization, resulting in the altered outcomes of the N deposition. In order to explore the effects of a severe wildfire on the retention of deposited N, we investigated the fates of newly deposited N in burned and unburned boreal larch forests by applying ¹⁵NH₄NO₃ tracers to the forest floors. Results showed that total ecosystem retention for the deposited N was 60% in the forest recovering from a severe wildfire burned five years ago, significantly lower than in the unburned mature forest (89%). The difference was mainly attributed to the substantially lower retention in vegetation (8.3%) in the burned site than in the unburned forest (32.4%), as tracer recoveries in soil were similar (51.2 and 56.6%, respectively). Although most ¹⁵N tracer was immobilized in organic soil in both burned and unburned forests (33 and 47%, respectively), a noticeably higher amount of ¹⁵N was found in mineral soil in the burned forest (19%) than in the unburned forest (10%), suggesting mineral soil as a significant sink for N deposition in the burned forest. A higher total ¹⁵N retention in the unburned forest implies that more new N input may stimulate C sequestration and promote the productivity of the Eurasian boreal forest under the background of atmospheric N deposition. However, a considerable amount of deposited N may be lost from the disturbed boreal larch forest ecosystem after a severe wildfire.

氮 (N) 沉积对森林的影响很大程度上取决于生态系统的氮状况和沉积氮的去向。北方森林通常是氮受限的生态系统，被认为比温带和热带森林在保留沉积氮方面更有效。作为北方森林的主要干扰，野火可能会减轻烧毁的生态系统中的氮限制并增加矿化，从而导致氮沉积结果的改变。为了探索严重野火对沉积氮保留的影响，我们通过在森林地面上应用¹⁵ NH ₄ NO ₃示踪剂，研究了烧毁和未烧毁的北方落叶松森林中新沉积氮的去向。结果显示，五年前从严重野火中恢复的森林中，沉积氮的生态系统总保留率为 60%，显着低于未燃烧的成熟森林 (89%)。差异主要归因于烧毁地点植被保留率 (8.3%) 明显低于未烧毁森林 (32.4%)，因为土壤中的示踪剂回收率相似（分别为 51.2% 和 56.6%）。尽管大多数¹⁵ N 示踪剂固定在烧毁森林和未烧毁森林的有机土壤中（分别为 33% 和 47%），但在烧毁森林的矿质土壤中发现的¹⁵ N 含量（19%）明显高于未烧毁森林(10%)，表明矿质土壤是烧毁森林中氮沉积的重要汇。未烧毁森林中较高的¹⁵ N 保留总量意味着，在大气氮沉降的背景下，更多的新氮输入可能会刺激碳固存并提高欧亚北方森林的生产力。然而，严重的野火后，受干扰的北方落叶松森林生态系统可能会损失大量沉积的氮。