石羊河下游民勤绿洲退耕地植被自然演替特征及物种多样性分析

Natural Vegetation Succession Characteristics and Species Diversity in Abandoned Lands in the Minqin Oasis,Downstream of the Shiyang River

采用重要值、Margalef物种丰富度指数、Shannon-wiener和Simpson多样性指数、Pielou和Alatalo均匀度指数对石羊河下游民勤绿洲不同年限退耕地自然恢复的植物群落进行了研究。结果表明:(1)石羊河下游民勤绿洲退耕地在50a自然恢复过程中共出现植物34种,14科,其中灌木6种,草本28种,分别占总物种数的17.65%和82.35%;藜科(8种)、禾本科(6种)、蒺藜科(4种)植物占总物种数的52.94%。(2)研究区退耕后50a植物群落演替经历为:田旋花→藜→苦苣菜→骆驼蒿→骆驼蓬→盐生草→黑果枸杞→红砂→盐爪爪的演替过程。(3)群落物种丰富度和多样性指数均随退耕时间的延长而呈现出波动式下降的变化趋势,而均匀度指数则呈现出在退耕初期(1～5a)先下降然后呈波动式上升的变化趋势。研究表明,随着退耕年限的增加,群落物种组成逐渐减少,植物群落演替向前发展的大致经历分为4个阶段:退耕1～5a为一年生草本和宿根植物迅速恢复阶段,退耕5～15a为一年生草本植物向多年生草本演替阶段,退耕15～30a为多年生草本向多年生灌木演替阶段,退耕30～50a为多年生灌木植物稳定阶段。

Studied on the natural recovery plant community in abandoned lands in the Minqin Oasis,downstream of the Shiyang River,which developed in deferent years by the index of the important value,species richness Margalef index,Simpson and Shannon-wiener diversity index,Alatalo and Pielou evenness index.The result shows that：（1）Plants of 34 species spread over 14 families live through fifty years appeared in abandoned lands in the study area.Shrubs was 6 species and herbs was 28 species among them,which were 17.65% and 82.35% respectively.The goosefoot family（8 species）,the grass family（6 species）,caltrop family（4 species） were 52.94% among them.（2）The following process of the plant community succession experienced in fifty years in study area：Convolvulus arvensis→Chenopodium album→Sonchus oleraceus→Peganum nigellastrum→Peganum harmala→Halogeton glomeratus→Lycium ruthenicum→Reaumuria soongorica→Kalidium foliatum.（3）Fluctuated downtrend showed by species richness and diversity index with the succession time growth.Downtrend in the first stage （1～5a） then fluctuated uptrend in the second stage showed by evenness index.Above all,the number of the species gradually reduced along with the development of plant community succession towards positive direction in abandoned lands,which experienced four stages,that was,the rapid recovery stage （1～5a） of annual herbaceous and perennial root plants,annual herb successes to perennial herb stage （5～15a）,perennial herbs successes to perennial shrub stage （15～30a）,perennial shrub plant arrived a stable relatively stage （30～50a）.