摘要
对塔里木河下游不同退化程度的4个典型断面进行了植被和土壤种子库的取样调查,采用种子萌发试验研究了不同退化区植被和土壤种子库的特征,结果表明:(1)塔里木河下游地表植被表现为严重的逆行演替,具体体现为胡杨林都为过熟林,几乎没有胸径在10 cm以下的幼林;植被盖度、密度和多样性指数均维持在一个较低的水平上;随退化程度不断加重,地表植被中草本植物的相对密度、相对盖度和相对频度逐渐降低,而灌木和乔木的相对密度、相对盖度和相对频度逐渐增加;(2)研究区土壤种子库的基本特征是:土壤种子库种类贫乏、密度低、多样性指数和相似性系数不高;(3)随退化程度的加重,土壤种子库物种数不断减少、密度明显下降、优势种组成趋于单一、表层种子库比例升高、1年生草本植物占优势逐渐向多年生草本植物和灌木植物转变及土壤种子库物种组成与地上植被物种组成上差异显著。
Four typical monitoring transects (C transect,E transect, G transect and H transect) along the lower reaches of Tarim river were selected. The results showed the following important points. ( 1 ) From the medium to extremely degraded regions, the relative density, relative cover and relative frequency of the annuals and perennials decrease gradually, while the relative density, relative cover and relative frequency of the shrub and arbor gradually increase, although the cover and the diversity of the vegetation tend to decline. (2) A total of fifteen species was found in the soil seed bank in the lower reaches of Tarim River, but the numbers of species decreased with increasing level of degradation. The seed bank density ranged from 250 -- 2013 seed/m2, but the results showed marked differences in the seed bank density along the degradation gradients ( F = 7. 922, P 〈 0. 05 ). The decline rates varied among different degradation regions. ( 3 ) The vertical distribution of the seed bank was characterized occupied 71%, 6 -10cm occupied 19%, 11 by a decr.ease of the seed bank density with increased depth : 0 -- 5cm 30cm occupied 10%. In the medium degraded region, the life form of the seed bank was dominated by annuals, but the life form shifted from annual to perennials and shrubs with increasing level of degradation. (4) The Sorensen's similarity coefficient between the seed bank and the standing vegetation was low, averaged O. 219. The number of co-occurring species both in the seed bank and the standing vegetation decreased with increasing level of degradation.
出处
《生态学报》
CAS
CSCD
北大核心
2008年第8期3626-3636,共11页
Acta Ecologica Sinica
基金
中国科学院“西部之光”资助项目
国家自然科学基金资助项目(304703293060009340671036)~~
关键词
不同退化区
地表植被
土壤种子库
塔里木河下游
: different degradation regions
soil seed bank
standing vegetation
lower reaches of Tarim River