巫山高山移民迁出区不同弃耕年限对植物物种多样性的影响

The effects of different restoration years on plant diversity in Wushan′s alpine emigrant region

以典型高山移民迁出区耕地(A1)、弃耕1a(A2)、弃耕5a(A3)、弃耕8a(A4)、弃耕5a生长大量白花银背藤(R1)为研究对象,采用空间序列代替时间序列的方法,比较不同弃耕年限植物重要值(P)、Margalef丰富度指数(R)、Shannon多样性指数(H′)、Pielou均匀度指数(Jw)、Simpson优势度指数(D)、Jaccard相似性指数(Cj)、Sorenson相似性指数(Cs)及多样性阈值(Dv),旨在探究不同退耕年限对植物物种多样性和群落结构的影响。结果显示,随弃耕年限增加,群落结构从草本+灌木转变为草本+灌木+乔木,群落优势物种由喜阳的一年生或多年生草本转变为耐阴的多年生草本;草本层和灌木层植物物种多样性随着演替年限的延长而增长,在演替的中后期达到最大值;A2与A3间群落的相似性指数最大;对不同弃耕年限样地植被群落多样性进行评定,都未达到“较好Ⅲ”级别,还需长期的恢复。恢复过程中注意对白花银背藤的监测,防止植物入侵。

This study examined cultivated land(A1)and cultivated land abandoned for one(A2),five(A3)and eight(A4)years,as well as the arable land abandoned for five years with the growth of Argyreia seguinii(R1)in Wushan′s alpine emigrant region.The method of space series replacing time course was used to compare the plant diversity and community structure among different abandonment periods in terms of importance value(P),Margalef richness index(S),Shannon diversity index(H′),Pielou evenness index(Jw),Simpson dominance index(D),Jaccard similarity index(Cj),Sorenson similarity index(Cs)and threshold of plant species diversity(Dv).The results indicated that,as the abandonment period increased,the community structure transformed from a shrub?herb(1—2 species)community to an arbor?shrub?herb community and the dominant plants changed from heliophilous annuals or perennial herbs to shade?loving perennial herbs.For the herb and shrub layers,the plant diversity followed the same rules:its maximum appeared in the medium or late periods and the similarity index was the highest between A2 and A3.After evaluating the situation of plant?species diversity over the different abandonment periods,it is clear that plant restoration failed to reach the“Well(Ⅲ)”level.Plant restoration required a long period of time before it was able to achieve a“Rich(Ⅱ)”degree of diversity.The growth of Argyreia seguinii should also be monitored during restoration to prevent it from invading plant.