黄河源区人工草地植被群落和土壤养分变化

[目的]研究黄河源区不同年限人工草地植被群落特征和土壤养分的动态变化,揭示高寒地区人工草地稳定机制与演替规律,为退化高寒草甸(湿地)的近自然恢复和缩短退化草地恢复时间提供理论依据。[方法]选择黄河源区青海省玛沁县3,11,17 a单播垂穗披碱草人工草地,对植被与土壤养分特征进行调查。[结果]随着种植年限增加,人工草地优势种垂穗披碱草盖度降低,植物总盖度、生物结皮盖度、杂类草盖度以及生殖枝数量呈倒"V"型变化,而原生植被莎草科植物盖度、物种多样性逐渐增加,17 a人工草地中莎草科植物的盖度是3,11 a的10倍;人工草地土壤养分中全氮、全钾、速效氮、速效钾以及有机质随年限增加呈现积累趋势,土壤pH值逐渐趋于中性。土壤全氮含量在不同恢复年限之间差异最大,平均准确率降低度为25.71,有机质含量次之,其平均准确率降低度为18.55,而全钾含量及均匀度指数最小,平均准确率降低度均小于5。[结论]高寒地区人工草地群落结构和土壤营养随着建植时间的延长在逐渐恢复,建植17 a的人工草地土壤全氮、有机质含量仅是原生高寒草甸土壤的50%左右,因此,17 a人工草地土壤养分完全恢复还需要较长时间。

Variation of Vegetation Community and Soil Nutrients of Artificial Grassland in Source Area of Yellow River

[Objective] The variation of vegetation community and soil nutrients in artificial grassland was studied and the long-term successional mechanism of artificial grasslands was explored in order to provide theoretical basis for the near-natural restoration of degraded alpine meadow (wetland).[Methods] The vegetation communities and soil nutrients of artificial grassland with different planting years (3, 11 and 17 years) were investigated in Maqin County of Qinghai Province, the source region of the Yellow River. Random forest analysis was used to determine the variation of vegetation community and soil nutrient characteristics of artificial grassland under different restoration years.[Results] The coverage of dominant species Elymus nutans decreased with the increase of restoration years, while the total coverage, biological crust coverage, weed coverage and reproductive branch number showed an inverted "V" shape of variation. The Cyperaceae coverage and species richness increased gradually with the increase of restoration years. The coverage of Cyperaceae in 17 years artificial grassland was 10 times of that in 3 and 11 years. The total nitrogen, total potassium, available nitrogen, available potassium and organic matter in soil increased with the increase of restoration years. The soil pH value tended to be neutral with the increase of restoration years. The greatest differences among vegetation with different restoration years was the soil total nitrogen content, with the average accuracy degraded about 25.71. Followed by the organic matter content, the average accuracy degraded about 18.55. The differences of total potassium content and Pielou index among vegetation with different restoration years were the smallest, and the average index degraded was less than 5.[Conclusion] The vegetation community structure and soil nutrient of artificial grassland with 17 years restoration are gradually recovering, but the soil total nitrogen and organic matter content of the artificial grassland is only half of the original alpine meadow soil, and it will take a long time for the soil nutrient to recover completely.