Despite the fact that winter lasts for a third of the year in the temperate grasslands, winter processes in these ecosystems have been inadequately represented in global climate change studies. While climate change increases the snow depth in the Mongolian Plateau, grasslands in this region are also simultaneously facing high pressure from land use changes, such as grazing, mowing, and agricultural cultivation. To elucidate how these changes affect the grasslands’ winter nitrogen (N) budget, we manipulated snow depth under different land use practices and conducted a 15NH415NO3-labeling experiment. The change in 15N recovery during winter time was assessed by measuring the 15N/14N ratio of root, litter, and soils (0–5 cm and 5–20 cm). Soil microbial biomass carbon and N as well as N2O emission were also measured. Compared with ambient snow, the deepened snow treatment reduced total 15N recovery on average by 21.7% and 19.2% during the first and second winter, respectively. The decrease in 15N recovery was primarily attributed to deepened snow increasing the soil temperature and thus microbial biomass. The higher microbial activity under deepened snow then subsequently resulted in higher gaseous N loss. The N2O emission under deepened snow (0.144 kg N ha−1) was 6.26 times than that of under ambient snow (0.023 kg N ha−1) during the period of snow cover and spring thaw. Although deepened snow reduced soil 15N recovery, the surface soil N concentration remained unchanged after five years’ deepened snow treatment because deepened snow reduced soil N loss via wind erosion by 86%.

中文翻译：

---

加厚的积雪改变了温带草原非生长季节对氮流失的生物和非生物控制

尽管温带草原的冬季持续了一年的三分之一，但这些生态系统中的冬季过程在全球气候变化研究中并未得到充分体现。在气候变化增加蒙古高原积雪深度的同时，该地区的草原也同时面临着土地利用变化的高压，如放牧、割草和农业耕作。为了阐明这些变化如何影响草原的冬季氮 (N) 收支，我们在不同的土地利用实践下操纵了雪深，并进行了 15NH415NO3 标记实验。通过测量根、凋落物和土壤（0-5 厘米和 5-20 厘米）的 15N/14N 比率来评估冬季 15N 恢复的变化。还测量了土壤微生物生物量碳和 N 以及 N2O 排放。与周围的雪相比，加厚的雪处理使第一个和第二个冬季的总 15N 恢复平均分别减少了 21.7% 和 19.2%。15N 恢复的减少主要归因于积雪加深增加了土壤温度，从而增加了微生物生物量。积雪下较高的微生物活性随后导致较高的气态氮损失。在积雪和春季解冻期间，深雪下的 N2O 排放量（0.144 kg N ha-1）是环境雪下（0.023 kg N ha-1）的 6.26 倍。尽管积雪降低了土壤 15N 的恢复，但经过 5 年的积雪处理后，表层土壤 N 浓度保持不变，因为积雪减少了 86% 的风蚀造成的土壤 N 损失。第一个和第二个冬天分别为 2%。15N 恢复的减少主要归因于积雪加深增加了土壤温度，从而增加了微生物生物量。积雪下较高的微生物活性随后导致较高的气态氮损失。在积雪和春季解冻期间，深雪下的 N2O 排放量（0.144 kg N ha-1）是环境雪下（0.023 kg N ha-1）的 6.26 倍。尽管积雪降低了土壤 15N 的恢复，但经过 5 年的积雪处理后，表层土壤 N 浓度保持不变，因为积雪减少了 86% 的风蚀造成的土壤 N 损失。第一个和第二个冬天分别为 2%。15N 恢复的减少主要归因于积雪加深增加了土壤温度，从而增加了微生物生物量。积雪下较高的微生物活性随后导致较高的气态氮损失。在积雪和春季解冻期间，深雪下的 N2O 排放量（0.144 kg N ha-1）是环境雪下（0.023 kg N ha-1）的 6.26 倍。尽管积雪降低了土壤 15N 的恢复，但经过 5 年的深雪处理，表层土壤 N 浓度保持不变，因为积雪减少了 86% 的风蚀土壤 N 损失。积雪下较高的微生物活性随后导致较高的气态氮损失。在积雪和春季解冻期间，深雪下的 N2O 排放量（0.144 kg N ha-1）是环境雪下（0.023 kg N ha-1）的 6.26 倍。尽管积雪降低了土壤 15N 的恢复，但经过 5 年的积雪处理后，表层土壤 N 浓度保持不变，因为积雪减少了 86% 的风蚀造成的土壤 N 损失。积雪下较高的微生物活性随后导致较高的气态氮损失。在积雪和春季解冻期间，深雪下的 N2O 排放量（0.144 kg N ha-1）是环境雪下（0.023 kg N ha-1）的 6.26 倍。尽管积雪降低了土壤 15N 的恢复，但经过 5 年的深雪处理，表层土壤 N 浓度保持不变，因为积雪减少了 86% 的风蚀土壤 N 损失。