桂西喀斯特植被恢复演替过程中物种多样性变化

Species Diversity in the Process of Vegetation Succession in Karst Area in Western Guangxi

桂西喀斯特地区石漠化后,植被自然恢复演替过程可分成草丛阶段、草灌阶段、藤刺灌丛阶段、次生乔林阶段和顶级群落阶段.以空间代替时间选取典型样地,分析了各阶段群落的物种组成,应用物种丰富度、Simpson指数、Shannon指数和Pielou均匀度指数分别研究各演替阶段草本层、灌木层、乔木层和群落总体的物种多样性.结果表明:在植被演替过程中,除草本层外,各生活型物种丰富度从草丛阶段开始增加,到次生乔林阶段达到峰值.草本层物种丰富度和Shannon指数略有波动,Simpson指数和均匀度都逐渐下降,到顶级群落阶段达到最低;灌木层、乔木层和群落总体各测度指数均表现为先增加后下降的趋势,但各测度指数达到峰值的阶段不同.草丛阶段物种多样性为草本层大于灌木层;进入草灌阶段以后,灌木层多样性上升并逐渐超过草本层;当乔木出现后,乔木层多样性最低.

The process of natural succession of restoring vegetation in western Guangxi after rocky deserti-fication of Karst area appearing was divided into the herbosa stage, the stage of herbosa-shrub, the stage of vine-shrub, the stage of subaltern tree forest and the climax stage. Typical quadrats were set up by using space instead of time. The species composition was analyzed in each stage and the species diversity in the layers of herb, shrub, tree and community at different successional stages was measured by the meth- ods of species abundance, Simpson index, Shannon index and Pielou＇s evenness index. The results showed that, with the exception of the herb layer, the species abundance in all layers rose steadily when the suc- cession developed from the herbosa stage, and reached the maximum in the stage of subaltern tree forest. In the herb layer, species abundance and Shannon index fluctuated but Simpson index and evenness index decreased gradually, and reached the minimum in the climax stage. Simpson index, Shannon index and Pielou＇s evenness index first increased, followed by a decline, but the stage at which the index reached its maximum was not consistent. Diversity indices of the herb layer were higher than those of the shrub layer in the stage of herbosa. When the succession entered into the stage of herbosa-shrub, diversity indices of the shrub layer rose and exceeded those of the herb layer. Diversity indices of the tree layer were the lowest from the time when arbor appeared.