氮素配施对三江源区退化高寒草甸植被和土壤的影响

三江源区草地退化严重威胁我国的生态安全，因此，研究恢复措施对草地的影响有重要意义。本研究以青海省果洛藏族自治州轻度退化高寒草甸为研究样地，通过三种不同类型氮素(尿素CH₄N₂O、硫酸铵(NH₄)₂SO₄和硝酸钾KNO₃)的九种组合配施，分析氮素配施后退化高寒草甸群落特征和土壤养分的变化，以探究不同类型氮素配施对退化高寒草甸恢复效果。研究结果表明，与对照相比，氮素配施显著提高了群落初级生产力(P<0.05),且生物量随着氮素配施量呈先增加后降低趋势，但对植物群落多样性无显著影响；土壤中速效氮和硝态氮呈现降低趋势(P<0.05),但有机碳、全氮、全磷和铵态氮含量无显著变化；利用主成分分析，通过综合评价植被指标和土壤指标，筛选出恢复该区域退化高寒草甸的最佳氮素配施量为47.2 g·m^-2硫酸铵+72.2 g·m^-2硝酸钾+21.6 g·m^-2尿素，为退化高寒草甸的恢复提供理论依据。

Effects of Nitrogen Combined Application on the Vegetation and Soil of Degraded Alpine Meadow in the Three-River Headwaters Region

The degradation of grassland in Three-River Headwaters Region is a serious threat to our ecological security, so it is of great significance to study the effects of grassland restoration measures on grassland. In this study, a slightly degraded alpine meadow in Guoluo Tibetan Autonomous Prefecture of Qinghai Province was selected as the research sample. To explore the effect of different nitrogen combined application on the restoration of degraded alpine meadow, we analyzed the community characteristics and soil nutrient changes of degraded alpine meadow after the applications of nine nitrogen combinations from three different types of nitrogen (urea CH₄N₂O, ammonium sulfate (NH₄)₂SO₄ and potassium nitrate KNO₃). The results showed that compared with the control, nitrogen combined application significantly increased community primary productivity (P<0.05), but had no significant effect on plant community diversity. The available nitrogen and nitrate nitrogen in the meadow soil showed a decreasing trend (P<0.05), but the contents of organic carbon, total nitrogen, total phosphorus and ammonium nitrogen had no significant changes. Based on the principal component analysis, the optimal combining rate of nitrogen application rate for the restoration of alpine meadows was selected as 47.2 g·m^-2 ammonium sulfate + 72.2 g·m^-2 potassium nitrate + 21.6 g·m^-2 urea, which provided a theoretical basis for of the nitrogen application for the restoration of degraded alpine meadow.