桉树人工林物种多样性变化特征

为了探讨大面积人工种植桉树林中植被类型和物种多样性的变化，以云南省西南部56.3万亩桉树人工林及其周围环境为研究区域，通过群落学调查，运用重要值、多样性、丰富度、均匀度等指标，统计分析桉树人工林、次生季风常绿阔叶林(以下简称次生林)和撂荒地3种不同植被类型的结构、种类组成和物种多样性。结果表明，桉树人工林中植被经过一定时间的演替会达到一定的丰富度，植物物种数和个体总数呈现出复杂性变化的特点，但规律性并不明显。桉树林样地中出现植物135种，隶属73科97属，草本层为最发达的一层；次生林样地中出现植物270种，隶属146科189属，乔木层为最发达层；撂荒地样地中出现植物105种，隶属74科104属，无乔木层。以样点9为例，类似立地因子的桉树林乔木层、灌木层和草本层的重要值Iv与其他2种植被类型相比差异较为明显。统计分析显示，桉树林多样性指数D值和H值、均匀度指数J值显著低于次生林(p<0.05)，在海拔1700 m以下显著低于撂荒地(p <0.05)，而1700m以上略高于撂荒地。桉树(Eucalyptus spp. )对植物群落多样性的影响与造林前的土地利用类型有关，在轮歇的撂荒地和低效灌木林地上发展桉树林不仅可以提供木材或纸浆材资源，而且还能够丰富植被结构和增加植物群落多样性。

Comparison of structure and species diversity of Eucalyptus community

To explore the impacts of Eucalyptus spp. planted in a large scale on the variation of type of vegetation and species diversity, community structure, species composition and diversity among Eucalyptus forest, secondary forest and old field were studied in the 563 thousand Mu of Eucalyptus forest located in southwest Yunnan province, using important value, diversity, richness and evenness by community investigation. The results indicated that the vegetation of Eucalyptus forest reached to some somewhat species richness, and the number of species and individuality took on complicated variations but without obvious regularity after a certain succession. There were 135 species belonging to 73 families and 97 genera in the Eucalyptus forest, among which the herbaceous layer was the most developed one. The secondary forest had 270 species belonging to 146 families and 189 genera, and the tree layer was the more developed one than two other layers. The old filed included 105 species of 74 families and 104 genera without tree layer. Taking plot 9 for instance, under the similar site factors, the important value Iv among three layers, the Eucalyptus forest had very significant difference comparing with the secondary forest and the old field. Meanwhile, the statistical analysis showed that diversity indices as the Simpson D, Shannon-Wiener H and homogeneity index Pielou J of the Eucalyptus forest were significantly lower than those of the secondary forest(p<0.05). However, below the elevation of 1700m, diversity indices as the Simpson D, Shannon-Wiener H and homogeneity index Pielou J of the Eucalyptus forest were significantly lower than those of the old filed(p<0.05) , which were a little higher over 1700m of elevation. All these results illustrated that the structure and species diversity of the Eucalyptus forest were related to land -use type before which was planted. If planted in the old field and inefficiency shrubbery land, the Eucalyptus forest can flourish community structure and species diversity.