桂西南喀斯特植被群落特征研究

采用"空间代替时间"方法建立退化群落自然恢复演替系列,以"最优分割法"划分群落演替阶段,对广西西南部喀斯特植被群落特征进行了研究。研究表明森林群落在群落结构上分为乔木层、灌木层和草本层3个层次,乔木层树木高度多在20 m以下,胸径在12 cm以下个体可达89.85%;灌木层个体高度一般不超过2 m,以乔木层幼苗幼树居多;草本层高度在0.5 m以下。草本、灌木群落所处生境比较恶劣,多为耐旱耐瘠薄单优群落,物种组成单一,群落高度3 m以下。群落生物多样性总体呈上升趋势,而均匀度呈下降趋势。Simpson指数在演替初期为0.76左右;演替中期上升为0.81~0.94;而演替后期下降为0.73~0.94。Shannon-Wiener指数由演替初期的1.59上升到演替中期的2.01~3.47,到演替后期下降为1.31~2.67。群落均匀度指数JD在演替初期为0.029~0.095;到演替中期下降为0.016~0.059;在演替后期群落均匀度上升到0.06以上。研究区域植被群落特征与经典演替理论群落特征变化有所不同,但与生态系统在适度干扰下多样性较高的适度干扰理论相一致,说明桂西南喀斯特生态系统经常受到外界干扰。

Study on community characters of Karst vegetation in the southwest of Guangxi

The "time-specific method" and "division method of optimization" were used to study the community characters of Karst vegetation in the Southwest of Guangxi.There are three layers in forest communities including tree layer,shrub layer and grass layer.Most trees' height is below 20 m,while the diameter of breast height is under 12 cm.The height of shrub layer is not higher than 2 m mainly consisting of seedlings of tree layer while the grass layer is under 0.5 m.The grass communities and shrub communities are most found in barren eco-environment.On the other hand,the biodiversity has changed greatly during the succession.The Simpson index is about 0.76,and the Shannon-Wiener index is 1.59 at the initial stage of community succession.Two indexes reach 0.81～0.94 and 1.31～2.67 respectively in the middle succession stage.However,the community biodiversity decreases to a stable level at the succession end.The evenness index JD is 0.029～0.095 at the initial stage of community succession,0.016～0.059 at the middle stage,and 0.06～0.09 at the succession end.The biodiversity is different from the classic succession theory,but it is highly consistent with the intermediate disturbance hypothesis.These shows the Karst ecosystems in the Southwest of Guangxi are influenced by disturbances constantly.