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以祁连山东段旱泉沟小流域为例,通过连续6年的定位观测,研究了紫花苜蓿人工草地退化特征.结果表明:紫花苜蓿人工草地建植以来,草地群落的盖度逐年下降,而群落密度增加,草层高度呈波动变化,地上生物量呈单峰曲线变化,最大值出现在建植后第3年;草地的物种数由7种增加到16种,物种替代速率为2.5～5.5,群落的Shannon-Wiener多样性指数呈上升趋势,Pielou均匀度指数表现出增减交替趋势,而Simpson优势度指数呈下降趋势.建植第5年,紫花苜蓿出现了自然稀疏,干草产量下降至129.8 g/m~2,草地裸斑增加、质量下降,部分草地已失去利用价值.2003-2008年人工草地群落经历了紫花苜蓿、多年生杂类草、多年生禾草优势阶段,草地退化严重,割草能力丧失,群落结构和功能趋于撂荒地演替格局.
Taking the Hanquangou catchment in the eastern part of Qilian Mountains as an example, the degradation characteristics of alfalfa artificial grassland were studied through six years of continuous observation, and the results showed that the cover of grassland community decreased year by year since the establishment of alfalfa artificial grassland, The density increased, the height of grassland fluctuated, the aboveground biomass showed a single peak curve, the maximum appeared in the third year after planting; the number of species in grassland increased from seven species to 16 species, the species replacement rate was 2.5-5.5, The Shannon-Wiener diversity index of the community showed an upward trend, while the Pielou evenness index showed an increasing / decreasing trend, while the Simpson dominance index showed a decreasing trend. In the fifth year of planting, alfalfa appeared naturally sparse and hay output decreased to 129.8 g / m ~ 2, bare grass spot increased and the quality decreased, some of the grasslands had lost their value.The artificial grassland community experienced the dominant stages of alfalfa, perennial grass and perennial grass from 2003 to 2008, Capacity loss, community structure and function tended to abandon land succession pattern.