放牧对高寒小嵩草草甸冷季草场主要植物种群生态位的影响

对高寒小嵩草草甸冷季草场主要21种植物种群在不同放牧率下优势度、生态位宽度及生态位重叠规律的研究结果表明:1)经过两年的放牧,对照、轻度和中度放牧组的主要优势种均为小嵩草和垂穗披碱草,重度放牧组的主要优势种变成了小嵩草和鹅绒委陵菜;2)尽管枯草期小嵩草和高原早熟禾的适口性较好而被优先采食,但由于它们特有的耐牧、耐践踏等生物学特点,生态位宽度依然很大(0.948,0.901);垂穗披碱草尽管由于适口性和耐践踏性相对较差,但由于其株高优势,生态位宽度依然较大(0.815);青海野青茅和紫羊茅在枯草期由于适口性较好而耐践踏性相对较差,对放牧及由放牧引起的环境变化反应最为敏感,其生态位宽度很窄(0.302,0.416),说明放牧抑制了高大禾草层片的发育,为植株矮小的莎草科牧草和阔叶植物的生长创造了条件;3)鹅绒委陵菜和雪白委陵菜、高山紫菀和柔软紫菀之间生态位重叠的降低,是种间对资源利用上分化的结果,且生态位宽度较大的物种与其它种群间也有较大的生态位重叠,分布于放牧演替系列两个极端的种群间生态位重叠较小,说明物种的分布是既间断又连续的.

Effects of Grazing on the Major Plant Populations Niche in Alpine Kobrecia parva Meadow Cold-seasonal Pastureland

The four different stocking rates,dominances,niche breadths and niche overlaps for twenty-one main plant population in an alpine Kobrecia parva meadow cold-seasonal pasture were measured,and the results showed that: 1) Through grazing for two years,Kobrecia parva and Elymus natans were still major dominated plants in control,light grazing and moderate grazing plots,but Kobrecia parva and Potentilla anserine dominated in heavy grazing plot;2) although yaks in priority ingested dainty Kobrecia parva and Poa alpigena in withered period,their niche breadths were still very wide(0.948,0.901) because they were able to bear of grazing,drought and trampling and other biological characters.Besides,although Elymus natans was not ingested in priority duo to its bad dainty and biological character of enduring trampling,its niche breadth was still relatively wide(0.805) for its height,and niche breadths of D.kokonorica and Festuca rubra based on grazing gradients were all very narrow(0.302,0.416)for their good dainty and dad enduring trampling.Therefore,all these indicated that grazing restricted growth of high grasses and created a good environment for growth of short sedges;3) Niche overlaps between Potentilla anserine and P.bifurca,between Aster alpinus and A.flaccidus were relatively narrow(0.592,0.412),which could be seen as polarized result for resource utilization based plant species.And then it could be also seen that the species with grater niche breadths generally had greater niche overlaps with other species,and that the species distributing in two extremeness along grazing gradients had narrower niche overlaps each other,which indicated the distributing of species was continuous and discontinuous.