牦牛放牧率对小嵩草高寒草甸暖季草场植物群落组成和植物多样性的影响

Effects of Stocking Rates for Yak on Community Composition and Plant Diversity in Kobresia parva Alpine Meadow Warm-season Pasture

两年的牦牛放牧试验结果表明:在暖季草场,随着放牧率的提高,禾草和莎草类功能群的盖度、生物量及其组成与高度减小,它们与放牧率呈显著的负相关 P<0.05 可食杂草和毒杂草类功能群的盖度、生物量及其组成与高度增加,它们与放牧率呈显著的正相关 P<0.05 各功能群的盖度与生物量之间是显著的正相关关系 P<0.05 .对照草地由于没有牦牛的采食,群落由少数优势种植物所统治,群落结构趋于简单,物种组成贫乏,物种多样性和均匀度指数最小;轻度放牧牦牛选择采食对植物群落的影响较小,群落的物种丰富度指数、均匀度指数和多样性指数均不高;中度放牧提高了资源的利用效率,增加了群落结构的复杂性,草地的物种丰富度指数、均匀度指数和多样性指数均最高,该结果支持 中度干扰理论 ;重度放牧由于牦牛采食过于频繁,改变了植物的竞争能力,导致植物种的均匀度下降,多样性减少.不同放牧率草地群落的物种数 S 、丰富度指数 Ma 、多样性指数 Shan-non-Wiener指数H′和Simpson指数D 、均匀度指数 Pielow指数J′ 的排序为:对照<轻度放牧<重度放牧<中度放牧,优势度指数 Berger-Parke指数 的变化趋势则与之相反.

Effects of stocking rates for yak on community composition in K.parva alpine meadow had been studied for two years.The results showed:in warm-season pasture,with the increase of stocking rates,coverage,average height,aboveground and its percentage composition for functional groups of grasses and sedges decreased,and they were significantly and negatively correlated with stocking rates (P<0.05),and on the contrary,functional groups of palatable and toxic weeds increased,and they had a positively correlation with stocking rates (P<0.05).Besides,there was a significant and positive correlation between coverage and aboveground biomass of different functional groups (P<0.05).As for control grassland,the community dominated by a few plants,structure of that was simple and lack of species,which led to species richness,diversity and evenness index were minimum for grassland not grazed and ingested,and under light grazing,the influences of ingestion by yaks on plant community were very small,which caused species richness,diversity and evenness index were not high.However,moderate grazing increased utilizing efficiency of resources and complexity of plant community,and so species richness,diversity and evenness index were maximum,which supported 'hypothesis of intermediate disturbance',heavy grazing accompanying with frequent ingestion and serious influence on plant community,resulted in a low evenness,richness and diversity index.The order of species number (S),richness index (Ma),diversity index (Shannon-Wiener index H′ and Simpson index D),evenness index (Pielow index J′) under different stocking rates was:control<light grazing<heavy grazing<moderate grazing,but dominance index (Berger-Parke index Ⅰ) was contrary with them in order.