Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
PLoS One. 2011;6(11):e26506. doi: 10.1371/journal.pone.0026506. Epub 2011 Nov 2.
An understanding of the factors controlling plant community composition will allow improved prediction of the responses of plant communities to natural and anthropogenic environmental change. Using monitoring data from 1980 to 2009, we quantified the changes in community composition in Leymus chinensis and Stipa grandis dominated grasslands in Inner Mongolia under long-term grazing-exclusion and free-grazing conditions, respectively. We demonstrated that the practice of long-term grazing exclusion has significant effects on the heterogeneity, the dominant species, and the community composition in the two grasslands. The community composition of L. chinensis and S. grandis grasslands exhibited directional changes with time under long-term grazing exclusion. Under free grazing, the L. chinensis community changed directionally with time, but the pattern of change was stochastic in the S. grandis community. We attributed the divergent responses to long-term grazing exclusion in the S. grandis and L. chinensis grasslands to litter accumulation and changes in the microenvironment after grazing exclusion, which collectively altered the growth and regeneration of the dominant species. The changes in the grazed grasslands were primarily determined by the selective feeding of sheep during long-term heavy grazing. Overall, the responses of the community composition of the Inner Mongolian grasslands to long-term grazing exclusion and heavy grazing were divergent, and depended primarily on the grassland type. Our findings provide new insights into the role of grazing in the maintenance of community structure and function and therefore have important implications for grassland management.
理解控制植物群落组成的因素将有助于提高对植物群落对自然和人为环境变化的响应的预测能力。利用 1980 年至 2009 年的监测数据，我们量化了内蒙古长期禁牧和自由放牧条件下羊草和大针茅草原群落组成的变化。结果表明，长期禁牧对两种草原的异质性、优势种和群落组成有显著影响。在长期禁牧下，羊草和大针茅草原的群落组成随时间呈定向变化。在自由放牧下，羊草群落随时间呈定向变化，但大针茅群落的变化模式是随机的。我们认为，大针茅和羊草草原对长期禁牧的不同响应归因于禁牧后凋落物积累和微环境的变化，这些变化共同改变了优势种的生长和更新。放牧草地的变化主要取决于长期重度放牧期间绵羊的选择性采食。总的来说，内蒙古草原群落组成对长期禁牧和重度放牧的响应是不同的，主要取决于草地类型。我们的研究结果为放牧在维持群落结构和功能中的作用提供了新的见解，因此对草地管理具有重要意义。
