The Spatial Pattern and Interactions of Woody Plants on the Temperate Savanna of Inner Mongolia, China: The Effects of Alternating Seasonal Grazing-Mowing Regimes.
The Spatial Pattern and Interactions of Woody Plants on the Temperate Savanna of Inner Mongolia, China: The Effects of Alternating Seasonal Grazing-Mowing Regimes.
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中国内蒙古温带稀树草原木本植物的空间格局和相互作用：季节交替放牧-割草制度的影响
DOI：
10.1371/journal.pone.0133277
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Ahmad B
中科院分区：
文献类型：
--
作者：
Wang X;Zhang B;Zhang K;Zhou J;Ahmad B
白榆林为主的温带稀树草原广泛分布于蒙古高原森林草原交错带，是我国北方较为稳定的木本-草本复合生态系统。相对更多的注意力已经支付给典型草原地区的退化，而较少的重点放在这个典型的温带稀树草原在目前的管理制度下的继承。本研究在距牧民定居点一定距离的梯度上，设置3块沿着100 m×100 m的样地，对样地内的木本植物进行调查。空间点格局分析，以澄清这些木本植物的空间分布和相互作用。结果表明，老U。胸径≥ 20 cm的白榆树呈随机分布，中径的U. 3个样地中，5 cm ≤ DBH < 20 cm的矮树在较小尺度上呈聚集分布，在较大尺度上呈随机分布，幼林（DBH < 5 cm）很少或没有，幼苗（无DBH）均形成聚集。这些研究结果可以解释为交替季节放牧割草制度（围封在夏季，秋季割草和放牧在冬季和春季），灌木在所有3个地块存在沿着放牧梯度，窝藏旱生和中生灌木。其中，旱生灌木在较小尺度（0-5.5 m）上表现出明显的聚集性，而中生灌木在较大尺度（0-25 m）上表现出明显的聚集性，这可能是放牧压力和气候变化双重作用的结果。中乔木和幼苗显著促进旱生灌木的分布，并由于水分利用策略的差异而与中生灌木竞争。我们的结论是，实施替代放牧割草制度的结果，在旱生灌木入侵或存在，打破了正常的演替链，在美国。在这一典型的温带稀树草原生态系统中，这可能最终导致原来的树木为主的稀树草原退化为旱生灌木为主的稀树草原。
Ulmus pumila tree-dominated temperate savanna, which is distributed widely throughout the forest-steppe ecotone on the Mongolian Plateau, is a relatively stable woody-herbaceous complex ecosystem in northern China. Relatively more attention has been paid to the degradation of typical steppe areas, whereas less focus has been placed on the succession of this typical temperate savanna under the present management regime. In this study, we established 3 sample plots 100 m×100 m in size along a gradient of fixed distances from one herder’s stationary site and then surveyed all the woody plants in these plots. A spatial point pattern analysis was employed to clarify the spatial distribution and interaction of these woody plants. The results indicated that old U. pumila trees (DBH ≥ 20 cm) showed a random distribution and that medium U. pumila trees (5 cm ≤ DBH < 20 cm) showed an aggregated distribution at a smaller scale and a random distribution at a larger scale; few or no juvenile trees (DBH < 5 cm) were present, and seedlings (without DBH) formed aggregations in all 3 plots. These findings can be explained by an alternate seasonal grazing-mowing regime (exclosure in summer, mowing in autumn and grazing in winter and spring); the shrubs in all 3 plots exist along a grazing gradient that harbors xerophytic and mesophytic shrubs. Of these shrubs, xerophytic shrubs show significant aggregation at a smaller scale (0-5.5 m), whereas mesophytic shrubs show significant aggregation at a larger scale (0-25 m), which may be the result of the dual effects of grazing pressure and climate change. Medium trees and seedlings significantly facilitate the distributions of xerophytic shrubs and compete significantly with mesophytic shrubs due to differences in water use strategies. We conclude that the implementation of an alternative grazing-mowing regime results in xerophytic shrub encroachment or existence, breaking the chain of normal succession in a U. pumila tree community in this typical temperate savanna ecosystem. This might eventually result in the degradation of the original tree-dominated savanna to a xerophytic shrub-dominated savanna.