Complementary effects of disturbance by livestock and marmots on the spatial heterogeneity of vegetation and soil in a Mongolian steppe ecosystem
Complementary effects of disturbance by livestock and marmots on the spatial heterogeneity of vegetation and soil in a Mongolian steppe ecosystem
复制标题
DOI：
10.1016/j.agee.2009.09.009
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Y. Yoshihara;T. Okuro;B. Buuveibaatar;J. Undarmaa;K. Takeuchi
中科院分区：
文献类型：
--
作者：
Y. Yoshihara;T. Okuro;B. Buuveibaatar;J. Undarmaa;K. Takeuchi
在蒙古草原，家畜和穴居啮齿动物是栖息地的主要动物修改者。虽然放牧地和啮齿动物栖息地重叠，但牲畜和啮齿动物干扰对植物和土壤空间异质性的综合影响很少被评估。我们在四个地点中的每一个建立了研究小区：牲畜大量放牧的地点，有没有土拨鼠，以及没有放牧的地点，有没有土拨鼠。我们将每个样地划分成样方，调查植物种类组成和土壤养分特性，并利用非度量多维尺度分析计算了植被在三个空间尺度上的空间异质性。并计算了土样间的变异系数。放牧和非放牧样地的植被空间异质性差异不显著，但无论放牧与否，旱旱干扰下植被的空间异质性均高于无旱獭干扰下的空间异质性，而在粗略尺度上旱獭干扰下植被的空间异质性较低。在很小的范围内，牲畜放牧(有没有)和土拨鼠(有没有)的组合形成了独特的栖息地。此外，在较粗的尺度上，放牧区的植物种类组成与非放牧区的植物种类组成不同。退化指示植物物种的出现取决于放牧的存在，而不是放牧和土拨鼠的相加效应。土拨鼠只在未放牧的地块增加了退化指示物种的丰度。在较粗的尺度上，每一类草食动物都增加了土壤养分的空间异质性，但当两类草食动物共存时，这种影响就消失了。这些结果表明，家畜和土拨鼠的生态作用是互补的，而不是功能对等的。也就是说，家畜改变了整体植被组成，从而改变了景观尺度上的空间异质性，而土拨鼠则改变了局部尺度上的空间异质性。适当地控制牲畜放牧制度可以维持蒙古草原物种丰富的群落，而不会造成严重的土地退化。
In the Mongolian steppes, livestock and burrowing rodents are the main animal modifiers of the habitat. Although grazing lands and rodent habitats overlap, the combined effects of livestock and rodent disturbance on spatial heterogeneity of plants and soil have rarely been evaluated. We established study plots at each of four sites: sites heavily grazed by livestock, with and without marmots, and ungrazed sites, with and without marmots. We subdivided each plot into quadrats to survey the plant species composition and soil nutrient properties, and calculated the spatial heterogeneity of vegetation at three spatial scales using non-metric multidimensional scaling analysis. We also calculated the coefficient of variance among the soil samples. The vegetation's spatial heterogeneity did not differ significantly between grazed and ungrazed plots; however, it was higher under marmot disturbance than in the absence of marmots at a fine scale, but lower under marmot disturbance at a coarse scale, irrespective of livestock grazing. At a fine scale, unique habitats were formed by each combination of livestock grazing (presence/absence) and marmots (presence/absence). In addition, the plant species composition in the grazed plots was distinct from that in the ungrazed plots at the coarser scale. The occurrence of degradation-indicator plant species depended on the presence of grazing rather than on the additive effect of grazing and marmots. Marmots increased the abundance of degradation-indicator species only in the ungrazed plots. Each herbivore group increased the spatial heterogeneity of soil nutrients at coarser scales, but these influences were lost when both herbivore groups coexisted. These results show that the ecological roles of livestock and marmots are complementary, not functionally equivalent. That is, livestock modified the overall vegetation composition, and thereby modified spatial heterogeneity at the landscape scale, whereas marmots modified spatial heterogeneity at the local scale. Proper manipulation of the livestock grazing regime can maintain species-rich communities without serious land degradation in the Mongolian steppe.