羊草+大针茅草原群落退化演替机理的研究

MECHANISM OF DEGRADATION SUCCESSION IN LEYMUS CHINENSIS+STIPA GRANDIS STEPPE COMMUNITY

通过比较退化与未退化典型草原群落中主要植物种的个体数量特征和根系分布的差异 ,在内蒙古锡林郭勒盟白音锡勒牧场中国科学院草原生态系统定位研究站的实验样地上通过为期 11年 (1983～ 1993)对退化草原群落恢复演替过程中植物个体特征动态的监测 ,证明以节间缩短、叶片变短和根系分布浅层化为特征的植物个体小型化是在过度放牧所致草原退化中联系导因与结果的机理性中间环节。植物个体小型化使群落生产力水平下降 ;也使各个种群构建群落的功能衰退 ,并由此导致原来占据的资源空间被释放出来 ;释放出的资源诱使家畜不喜食的种群大量拓殖 ,从而出现优势种更替。因此 。

Characteristics of individual plants in a restoration area of a degraded typical steppe were monitored over an 11 ye ars period (1983～1993) in the experimental region of the Inner Mongolia Grassla nd Ecosystem Research Station of the Chinese Academy of Sciences that is in the Xilin Gole League, Inner Mongolia,China.Comparison of these characteristi cs and of the root system distribution of major plant species were subsequently made between the degraded community and primary community.It was concluded that th e plant individual miniaturization is the mechanistic intermediate link between o ver-grazing and degradation.Miniaturized individuals show the following charact eristics:shortened internodes,contracted leaf blades and a shallowly distributed root system.Individual plant miniaturization reduces community productivity a nd reduces the regenerative ability of populations.The space released by the min iaturization of original plants may then be infilled by abundant colonization of unpalatable plant species.The phenomenon of individual plant miniaturization a nd its ecological effects reveals the mechanism underlying the decreased product ivity and replacement of dominants that characterizes steppe community degradati on under overgrazing.