围封禁牧对若尔盖高寒沼泽化草甸物种组成和群落结构的影响

Effects of Grazing Exclusion on Species Composition and Community Structure of Alpine Wet Meadow on the Ruoergai Plateau

为评估围封禁牧与冬春放牧措施在若尔盖高寒沼泽化草甸的生态保护效益,对其围封禁牧7 a后的华扁穗草群落植株高度、地上生物量、物种丰富度等进行测量与分析。研究显示:(1)围封禁牧显著增加华扁穗草群落的植株高度、凋落物量(P<0.01),显著降低植株密度、地上生物量和物种丰富度(P<0.05);(2)围封禁牧样地的物种数下降5种,多数多年生杂类草退出群落,物种间正负关联比下降,群落稳定性降低;(3)植株高度与凋落物极显著正相关(P<0.01)、与物种丰富度显著负相关(P<0.05),而物种丰富度与凋落物极显著负相关(P<0.01)。结果表明:围封禁牧降低了若尔盖高寒沼泽化草甸的物种多样性及其植被生产力,冬春放牧可以有效地维持群落物种组成及其稳定性;围封禁牧引起的凋落物过量累积是高寒沼泽化草甸物种减少和群落稳定性降低的显著驱动因子。研究结果可为评价围封禁牧政策在不同类型湿地保护管理实践中合理性应用提供理论支撑和实验证据。

In order to evaluate the ecological protection benefits of grazing exclusion and grazing in winter and spring in Ruoergai alpine wet meadow,the plant height,aboveground biomass,and species richness of the Blysmus sinocompressus community were measured and analyzed after 7 years of grazing exclusion.The results found that:(1)The grazing exclusion significantly increased the plant height and litterfall amount(P<0.01),and significantly reduced the plant density,aboveground biomass and species richness(P<0.05);(2)The number of species in the grazing exclusion dropped by 5,most of the perennial weeds withdrew from the community,the positive-negative correlation ratio between species declined,and the stability of the community decreased;(3)Plant height was extremely significantly positively correlated with litterfall(P<0.01),and significantly negatively correlated with species richness(P<0.05),while species richness was extremely significantly negatively correlated with litterfall(P<0.01).The results indicated that grazing exclusion reduced the species diversity and vegetation productivity of Ruoergai alpine wet meadow,and grazing in winter and spring could effectively maintain the community species composition and stability.Excessive accumulation of litter caused by grazing exclusion is a significant driving factor for the decrease of species in alpine wet meadow and the decrease of community stability.This study elucidated the response mechanism of the alpine wet meadow ecosystem to grazing exclusion from the perspective of species composition and community structure,which can provide theoretical support and experiments for evaluating the rational application of grazing exclusion policies in different types of wetland protection and management practices evidence.