中文摘要：

以黄土高原清涧县丘陵沟壑区不同年限退耕地为研究对象,采用样方法对退耕地10a的群落变化进行调查,应用物种组成、Margalef丰富度指数、Simpson多样性指数、Shannon-Wiener指数等指标分析群落的物种组成以及多样性变化的规律。结果表明,该区群落内共有48种植物,分属于17科40属,其中禾本科（Poaceae）7属7种、豆科（Leguminosae）8属8种、菊科（Asteraceae）10属13种,分别占物种总数的14.6%、16.7%和27.1%;黄土高原丘陵沟壑区退耕地初期的优势种为菊科植物,随后依次为一年生草本植物、多年生草本植物;随着退耕时间的延续,群落物种的Margalef丰富度指数、Simpson多样性指数、Shannon-wiener指数整体呈现上升趋势;坡向对群落的物种组成有一定的影响,但不显著。

英文摘要：

A case study on abandoned lands was carried out in the hill and ravine region of Qingjian County by using sampling methods to analyze the variation of the community during the latest 10 years.Species composition,Margalef abundance index,Simpson index and Shannon-wiener index were used to analyze the variation of species composition and the species diversity of the community.The results indicated：（1） There were 48 species of 40 genera in 17 families,including 7 species of 7 genera in Poaceae,8 species of 8 genera in Leguminosae,13 species of 10 genera in Asteraceae.The percentage to Poaceae,Leguminosae,and Asteraceae was 14.6%,16.7% and 27.1%,respectively.（2） Plant species of Asteraceae family were the dominant species at early stage in the abandoned lands,followed by annual herbs and perennial herbs.（3）With the duration of abundance,Margalef abundance index,Simpson index and Shannon-wiener index showed increasing trend in this process.（4） Slope exposure could somewhat influence the species composition of the community,but not significantly.