Abstract:

Taking the alpine meadow, alpine steppe and swamp meadow ecosystems in the source area of the Yellow River on Qinghai-Tibet Plateau as the research objects, this paper tested the impacts of grassland degradation and artificial vegetation restoration on soil nutrient characteristics. The soil quality was evaluated to provide a theoretical basis for the management and utilization of alpine grassland in the source area of the Yellow River. Some interesting and innovative findings were obtained. (i) Vegetation degradation in alpine steppe significantly reduced soil water content, while no obvious effect on soil carbon content, nitrogen content, phosphorus content, potassium content, bulk density and pH were observed. The degradation of alpine meadow vegetation significantly decreased soil total carbon, total organic carbon, total nitrogen, soluble organic nitrogen, ammonium nitrogen, total phosphorus, available phosphorus and soil water content, but significantly increased soil nitrate nitrogen, bulk density and pH. Vegetation degradation in alpine meadow had no significant effect on soil total potassium and available potassium. (ii) Vegetation restoration in degraded alpine steppe can significantly increase soil total organic carbon, total nitrogen, soluble organic nitrogen, ammonium nitrogen, nitrate nitrogen, available potassium and soil water content. Vegetation restoration in degraded alpine steppe had no significant effect on soil bulk density, pH, total carbon, total phosphorus, total potassium and available phosphorus. After vegetation restoration of degraded alpine meadow, the contents of soil water content, soluble organic nitrogen, ammonium nitrogen, total potassium and available potassium could be significantly increased. Vegetation restoration on degraded alpine meadow showed little no effect on soil total carbon, organic carbon, total nitrogen, nitrate nitrogen, total phosphorus and available phosphorus. (iii) In 0-20 cm depth soil layer, the comprehensive evaluation results of soil quality are as follows: swamp meadow> alpine meadow > artificial grassland (5 years old)>artificial grassland (15 years old)>degraded alpine meadow>artificial grassland (4 years old)>alpine grassland>degraded alpine grassland. In conclusion, soil nutrient showed different characteristics among different types of alpine grassland ecosystems. The degradation of alpine meadow has a significant impact on soil nutritional characteristics. Vegetation restoration improved the soil quality of degraded grassland.

Key words: Qinghai Tibet Plateau, source area of the Yellow River, alpine grassland, physical and chemical properties of soil, quality evaluation

摘要：

以黄河源区高寒草甸、高寒草原和沼泽草甸生态系统为研究对象,分析草地退化和人工植被恢复措施对土壤营养特征的影响程度,评价黄河源区高寒草地土壤质量的基本状况,以期为黄河源区高寒草地的管理和利用提供理论依据。结果表明,（1）高寒草原植被退化显著降低了土壤含水量（P<0.05）,对土壤碳氮磷钾含量、土壤容重和土壤pH值均没有产生显著影响（P>0.05）;高寒草甸植被退化显著降低了土壤全碳、有机碳、全氮、可溶性有机氮、铵态氮、全磷、速效磷含量和土壤含水量（P<0.05）,显著增加了容重、pH和土壤硝态氮含量（P<0.05）,对土壤全钾和速效钾没有显著影响（P>0.05）。（2）在退化的高寒草原上恢复植被,可显著增加土壤有机碳、全氮、可溶性有机氮、铵态氮、硝态氮、速效钾含量和土壤含水量（P<0.05）,对土壤容重、pH、全碳、全磷、全钾和速效磷含量没有产生显著影响（P>0.05）;在退化高寒草甸上恢复植被,可显著提升土壤含水量、可溶性有机氮、铵态氮、全钾和速效钾含量（P<0.05）,对土壤全碳、有机碳、全氮、硝态氮、全磷、速效磷没有显著影响（P>0.05）。（3）在0—20 cm土层,土壤质量综合评价结果为：沼泽草甸>高寒草甸>人工草地 (5 a)>人工草地 (15 a)>退化高寒草甸>人工草地 (4 a)>高寒草原>退化高寒草原。综上,不同类型高寒草地生态系统土壤营养特征差异极大,高寒草甸的退化对土壤营养特征影响显著,植被恢复措施提高了退化草地的土壤质量。

关键词: 青藏高原, 黄河源区, 高寒草地, 土壤理化性质, 质量评价