Grazing management effects on plant species diversity in tallgrass prairie
Grazing management effects on plant species diversity in tallgrass prairie
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DOI：
10.2307/4003955
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发表时间：
2004-01-01
期刊：
影响因子：
--
通讯作者：
Owensby, CE
中科院分区：
文献类型：
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作者：
Hickman, KR;Hartnett, DC;Owensby, CE
在高草草原进行了为期6年的研究，以评估放牧管理(放牧密度和放牧制度)对植物群落组成和多样性的影响。处理包括按3种放牧密度(每动物单位3.8、2.8和1.8公顷)放牧整个季节(5月至10月)的放牧地点、未放牧的对照地点和在相同放牧密度范围内实行季末休牧轮牧制度的地点。每个季节使用最近点法对植物群落进行两次采样。放牧草原的原生植物物种多样性、物种丰富度和生长形态多样性均显著高于未放牧草原，且放牧密度越高，多样性越大。放牧下植物物种多样性的增加并不是杂草/外来物种增加的结果。放牧制度对植物多样性没有显著的影响，放牧密度与放牧制度的交互作用也不显著，说明动物密度是影响高寒草原植物物种多样性和组成的关键管理变量，动物密度的影响大于放牧制度的影响。放牧密度的增加降低了多年生优势高草的丰度，增加了C-4多年生中生牧草的丰度。在不同放牧处理中，多年生杂草的出现频率相对稳定。一年生杂草丰度因年份和放牧处理不同而不同。在取样的一半年份中，中等密度下的一年生杂草出现的频率最高。植物群之间的反应模式表明，一些物种可能主要对食草动物的直接影响做出反应，而另一些物种可能对食草动物对竞争关系或燃料负荷和火灾的空间格局的间接影响做出反应。因此，这项研究表明，大的放牧密度、火和年气候变化相互作用，影响了高草草原植物群落组成和多样性的格局。不同的管理措施，如放牧密度和放牧制度，对植物物种多样性和不同植物生长型或功能类群的相对丰富度的影响可能对草地群落的稳定性和生态系统功能产生重要影响。
A 6-year study was conducted in tallgrass prairie to assess the effects of grazing management (cattle stocking densities and grazing systems) on plant community composition and diversity. Treatments included sites grazed season-long (May to October) at 3 stocking densities (3.8, 2.8, and 1.8 hectares per animal unit), ungrazed control sites, and sites under a late-season rest rotation grazing system at this same range of stocking densities. Plant communities were sampled twice each season using a nearest-point procedure. Native plant species diversity, species richness, and growth form diversity were significantly higher in grazed compared to ungrazed prairie, and diversity was greatest at the highest stocking density. This enhancement of plant species diversity under grazing was not a result of increased frequency of weedy/exotic species. There were no significant effects of grazing system on plant diversity, nor any significant stocking density x grazing system interactions, indicating that animal density is a key management variable influencing plant species diversity and composition in tallgrass prairie and that effects of animal density override effects of grazing systems. Increasing cattle stocking densities decreased the abundance of the dominant perennial tall grasses, and increased abundance of the C-4 perennial mid-grasses. The frequency of perennial forbs was relatively stable across grazing treatments. Abundance of annual forbs varied among years and grazing treatments. In half of the years sampled, annual forbs showed the highest frequency under intermediate stocking density. Patterns of responses among plant groups suggest that some species may respond principally to direct effects of grazers and others may respond to indirect effects of grazers on competitive relationships or on the spatial patterns of fuel loads and fires. Thus, this study suggests that large grazer densities, fire, and annual climatic variability interact to influence patterns of plant community composition and diversity in tallgrass prairie. Effects of varying management such as stocking densities and grazing systems on plant species diversity and the relative abundances of different plant growth forms or functional groups may have important consequences for grassland community stability and ecosystem function.