北川河流域退耕还林还草地主要植物群落物种多样性研究

Studies on Species Diversity of Plant Community of the Converting Farmland in Beichuanhe Basin

对大通县北川河流域内不同植物群落全面考察的基础上,根据立地条件、植被及土地利用方式等因素,选取代表性地段,设置了24个标准地,应用丰富度指数、Gleason指数、Simpon指数、Shannon-Wienner指数和均匀度指数来综合分析物种丰富度、生态优势度、群落物种多样性和均匀度。结果表明:在不同的退耕时间序列上,随着时间的推移,群落逐渐趋于稳定,群落物种多样性和丰富度呈“小-大-小”的变化过程,而均匀度和优势度指数呈“大-小-大”的变化过程;对不同起源地的群落多样性,天然林>退耕地>耕地,且退耕多年地段的群落物种多样性接近于天然林。

The study was carried out in Beichuanhe basin of Datong county,Qinghai Province,where there is the demonstration site for Converting Cropland to Forest. Based on different communities in this area, the authors choose some representative areas, and set 24 standard localities according to the site factors ,vegetation and land utility mode. And species richness, ecological dominance,species diversity and evenness of community are comprehensively calculated by richness index,Glcason index, Simpon index, Shannon-Wienner index and evenness index. The results are as follows. （1）According to different converting time, the community is becoming more and more steady as time goes on. The Shannon-Winenner index and richness index can be showed as a＂small-big-small＇process and Simpon and evenness index showed as＂blg-small-big＂. （2）According to different places of origin,the level of the species diversity can be arranged from top to bottom as following： nature forest〉 converted farmland〉cuhivated farmland. The diversity of converted farmland is close to that of the nature forest after some years.