Alpine grasslands are undergoing severe degradation and are mainly restored through fencing. Numerous studies have explored the patterns, processes, and mechanisms of plant and soil during degradation, but few have been conducted on nitrogen (N) uptake by plant functional groups during restoration. An alpine meadow and an alpine steppe on the Tibetan Plateau were chosen to carry out in situ ¹⁵N labelling experiments in the forms of NH₄⁺, NO₃⁻, and glycine during restoration. Short-, moderate-, and long-term restoration periods were explored, and plants were classified by functional groups into grasses, sedges, and forbs. Our results found biomass of grasses increased and that of sedges decreased with restoration in alpine meadow. In alpine steppe, forbs gradually became dominant in the community biomass by 58% during restoration. Long-term restoration increased NH₄⁺ uptake by grasses in alpine meadow. The total N uptake rates by grasses increased, but by forbs decreased during restoration in alpine meadow. Restoration decreased the total N uptake rates of grasses and forbs in alpine steppe. Chemical niche in N uptake was discovered during long-term restoration in alpine meadow and during moderate-term restoration in alpine steppe. We conclude that restoration alters the biomass composition of grasses, sedges, and forbs in alpine grasslands and shifts N uptake partitions. Chemical niche in N uptake by different functional groups in grasslands during restoration can decrease the fierce competition for N. Our results provide a synthesis for plant N utilization from soil during restoration of degraded grasslands from the perspective of shifting N uptake strategies.

中文翻译：

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植物功能组在退化的高山草原恢复过程中改变了它们的氮吸收

高山草原正在严重退化，主要通过围栏恢复。许多研究探索了植物和土壤在退化过程中的模式、过程和机制，但很少有关于植物功能组在恢复过程中吸收氮 (N) 的研究。选择青藏高原高寒草甸和高寒草原进行NH ₄ ⁺、NO ₃ ^-形式的^{15 N}原位标记实验 , 和甘氨酸在恢复过程中。探索了短期、中期和长期的恢复期，并将植物按功能组分为草、莎草和杂草。我们的研究结果发现，随着高寒草甸的恢复，草的生物量增加，莎草的生物量减少。在高寒草原，在恢复过程中，杂草在群落生物量中逐渐占主导地位，占群落生物量的 58%。长期恢复增加NH ₄ ⁺被高山草甸的草类吸收。在高寒草甸恢复过程中，草的总氮吸收率增加，但杂草的总吸收率降低。恢复降低了高寒草原草和杂草的总氮吸收率。在高寒草甸的长期恢复和高寒草原的中期恢复过程中发现了氮吸收的化学生态位。我们得出结论，恢复改变了高寒草原中草、莎草和杂草的生物量组成，并改变了 N 吸收分区。恢复过程中草地不同官能团吸收氮的化学生态位可以减少对氮的激烈竞争。我们的研究结果从转变氮吸收策略的角度为退化草地恢复过程中土壤中植物氮的利用提供了综合。