放牧对环青海湖高寒草原主要植物种群生态位的影响  

Effects of grazing on niche of major plant populations in alpine steppe in Qinghai Lake Region

作　　者：郑伟[1,2] 董全民[2] 李世雄[2] 刘玉[1,2] 

机构地区：[1]青海大学研究生院,青海西宁810003 [2]青海省畜牧兽医科学院,青海西宁810016

出　　处：《草业科学》2013年第12期2040-2046,共7页Pratacultural Science

基　　金：国家自然基金项目(30960074;31370469);青海省自然基金项目(2012-Z-906)

摘　　要：以环青海湖高寒草原为研究对象,对不同放牧强度下草地植被进行调查,并运用Levins生态位宽度和Pianka生态位重叠指数对不同放牧率梯度下主要植物种群生态位特征进行计算,以期从生态位角度解释植物群落的放牧演替机制。结果表明,经过3年的放牧,群落优势种发生了改变,随着放牧强度的增加,适口性好的植物[紫花针茅(Stipapurpurea)、早熟禾(Poasp.)、萹蓄豆(Medicago ruthenica)等]优势度降低,家畜不喜食或不食的和耐牧的植物[披针叶黄华(Thermopsis lanceolata)、矮嵩草(Kobresia humilis)等]优势度增加。紫花针茅生态位宽度最大,披针叶黄华次之,分别为0.994和0.959,多裂委陵菜(Potentilla multifida)和多枝黄芪(Astragalus polycladus)环境适应能力较强,生态位宽度较大。在放牧率梯度上垂穗披碱草(Elymus nutans)和溚草(Koeleria cristata)的生态位宽度较小,说明放牧抑制了高大禾草的层片发育。生态位宽度较大的物种与其他种群间有较大的生态位重叠,生态位重叠度较小是种间对资源需求分化的结果。放牧使主要植物种群生态位发生了分化,随着放牧强度的增加,群落可能从以紫花针茅和早熟禾等为优势种群向以矮嵩草、高山嵩草(K.pygmaea)和披针叶黄华为优势种群的方向发展,表明生境有了明显的退化。因此,控制草地的放牧强度是维持种群健康发展的关键。Alpine steppe is the major vegetation community around Qinghai Lake Region. It is regarded as an important ecological barrier of the Qinghai-Tibetan Plateau and a rich site forage base for yak and sheep production. However, the alpine steppe vegetation degraded by overstocking. Therefore, it＇s important to study the effects of grazing on community of alpine steppe around Qinghai Lake Region. In this study, the vegetation under different grazing intensity were investigated, based on grazing trial for 3 years in alpine steppe around Qinghai Lak, pegion. Levins niche breadth and Pianka niche overlap index were used to cal- culate niche characteristics o najor plant populations under different grazing gradients to explain the mechanism of grazing succession of community. Our results showed that dominant species of community had changed after grazing 3 years. The dominance of plants with good palatability （Stipa purpurea, Poa sp. , Medicago ruthenica, etc. ） decreased and the dominance of plants with grazing resistance or bad pal- atability （Kobresia humilis, Thermopsis lanceolata, etc. ） increased with the increase of grazing intensity.S. 1）urpurea had the widest niche breadth, and after then was Thermopsis lanceolata, with the values being 0. 994 and 0. 959, respectively. Potentilla rnultifida and Astragalus polycladus had wider niche breadth because of its stronger environmental adaptation ability. The niche breadths of Elymus nutans and K. cristata under different grazing gradients were narrow, indicating that grazing restricted the growth of high grasses. Species with wider niche breadth had higher niche overlap with other species. The narrower niche overlap could be seen as the result of interspecific differentiation on resource utilization. The major plant populations had niche differentiation result from grazing. With increasing grazing intensity, commu- nity with S. purl）urea and Poa sp. being the dominant populations may be in degradation direction on com- munity with K. humilis, K. pygmaea and

关 键 词：放牧强度 高寒草原 优势度 生态位宽度 生态位重叠 

分 类 号：S812[农业科学—草业科学]