牦牛放牧模式对西藏高山嵩草草甸群落特征的影响

利用样方法对西藏高山嵩草（Kobresia pygmaea）草甸群落进行实地调查，分析了2010-2012年不同强度的牦牛放牧试验对植物群落动态和地上生物量的影响，以期为高寒牧区退化草地的恢复及草地高效利用提供理论指导。结果表明：适度放牧能提高物种多样性、丰富度、均一度和地上生物量，降低植物群落盖度；重度放牧降低植物群落的多样性和生物量；重度延迟放牧能缓减重度放牧对草地的不良影响；相关分析结果表明，植物群落盖度与均匀度、丰富度、植物密度、多样性和地上生物量成正相关。高山嵩草草甸的功能群随着放牧强度的增加而显著变化，其优势功能群多年生根茎型牧草高山嵩草和苔草（Carex moorcroftii）、多年生丛生型牧草紫花针茅（Stipa purpurea）的盖度和地上生物量随着放牧强度增加而下降。

Effects of Yaks Grazing Methods on the Community Characteristics of Kobresia pygmaea Meadow in Tibet

Effects of yaks grazing intensity and grazing years on the plant community dynamics and aboveground biomass of Kobresia pygmaea meadow in Tibet were studied using sampling methods in order to provide a theoretical basis for recovering and increasing the productivity of degraded grasslands in alpine pastoral region. The results showed that heavy grazing (HG) negatively influenced plant community diversity and aboveground biomass, whereas moderate grazing (MG) increased diversity, richness, evenness, aboveground biomass and reduced vegetation coverage. These values in delayed-moderate grazing (DHG) were higher than those in HG. Correlation analysis showed that coverage and evenness, richness, plant density, diversity and aboveground biomass were positively correlated. In addition, the functional groups of Kobresia pygmaea meadow significantly differed from different grazing intensities. The coverage and aboveground biomass of perennial rhizome grass(Kobresia pygmaea and Carex moorcroftii) and perennial bunch grass(Stipa purpurea), which constituted the dominant species of the ecosystem, decreased with the increase of grazing intensity.