【作者】 周伟磊；

【导师】 李景文；

【作者基本信息】 北京林业大学 ， 生态学， 2011， 硕士

【摘要】 荒漠绿洲既是整个荒漠生态系统的重要组成部分,也是干旱极端干旱区最为敏感的区域,以胡杨为建群种组成的荒漠河岸林是额济纳绿洲植被的主体。由于自然和人为的干扰,胡杨林遭受到严重的破坏,退化严重。目前,解决胡杨林及其生物多样性保护问题,重点在于胡杨林更新及其植物多样性的维持的研究。本文以额济纳荒漠绿洲胡杨林为研究对象,研究了植物多样性维持的机理以及更新状况,在此基础上提出该区域胡杨林生物多样性保护的对策。针对植物多样性组成特征进行了调查。基于各物种的重要值,群落被划分为14个区。通过计算Simpson指数、Shannon-Wiener指数、Pielou均匀度指数及区域Whittaker指数,来计算群落多样性,并通过对应分析法(CA)得到了样地的排序。研究表明：在整个研究区域生物多样性相对低,但由于不同样方生境的空间异质性、群落多样性很高(pw=8.09)。此外,研究了不同生境的生物多样性特征,以及生物多样性与诸如水分条件、群落成分和土壤条件等环境因素之间的关系。基于以上的分析,得出结论：水分和土壤的环境异质性维持了河岸带群落及其物种组成的多样性。目前,该区域胡杨林群落的维持主要依赖于胡杨的根蘖繁殖。通过对可能影响根蘖发生和生长的因素(土壤类型、水分和林分年龄)的控制试验发现：土壤类型为林下土,适宜水分含量为15%,林型为近熟林的三个因子水平组合最适宜胡杨根的不定芽的生长过程；土壤类型为河岸淤泥土、15%的含水量和成熟林的横走根,这三种水平的组合最有利于不定根萌芽的发生,在试验当中平均发生萌芽的数量为35.6个。5%的水分条件是不定芽发生的一个临界值,也是不定芽发育为根蘖过程中的一个限制因素。光照条件下适宜不定根萌蘖芽的发生,荫蔽的环境条件下更适合根蘖苗的生长。胡杨通过分布于地下的大量的横走根来产生萌芽,但是长出地面后在产生的萌芽的生境下不适宜其生长,造成根蘖苗有大面积发生但只有小部分成活的现象。更多还原

【Abstract】 Oasis is not only the most important part of desert ecosystem, but also the most sensitive region. Influenced by desert arid climate, desert riparian forest made up by Populus euphratica Oliv. is non-zonal vegetation as well as the main part of the Ejina oasis of Inner Mongolia. Due to the lack of understanding on the function of Populus forest on maintaining eco-balance in desert region, P. euphratica forest suffered havoc, withering phenomenon is very serious. Therefore, to solve the related problems concerning the P. euphratica forest and biodiversity conservation, it is crucial to move on to study the P. euphratica regeneration and the plant diversity under it.This study was conducted in P. euphratica forest in Ejina Oasist, and we investigated the regeneration and composition of Plant Diversity. Communities were divided into 14 associations on the basis of their species importance values. The Simpson’s index, Shannon-Wiener index, Pielou’s evenness index and the regional Whittaker’s index were applied to calculate community diversity. An ordination of the sample plots was carried out by correspondence analysis (CA). Biodiversity was relatively low across the entire study area, but there was high community diversity (βw=8.09) due to the spatial heterogeneity of habitats in different plots. In addition, we investigated the relationship between biodiversity and several environmental factors, such as water availability, community components and soil conditions. We conclude that the heterogeneity of soil and water availability drives community diversity patterns in riparian zones and species composition.At present, the regeneration of P. euphratica Forest communities maintain mainly depends on the root sprout breeding. It was found from the control experiment on the possible influential factors of the generation and growth of root sprouts, that the combination of soil below the forests, the proper moisture at 15% and the near-mature forest is the optimal condition for the growth of adventitious buds of roots of P. euphratica. While the combination of riparian puddled soil, the water content at 15% and the horizontal-went roots in nature forests is the best condition for the generation of sprouts of adventitious roots, and the average amount of sprouts in the experiment is 35.6. The water condition of the moisture at 5% is the critical condition for the generation of adventitious buds and is also one limiting factor during the development of adventitious buds becoming the root sprouts.It is proper to generate sprouts on adventitious roots under light while the shade environment is preferred by the seedlings on roots. With the help of the large amount of horizontal-went roots underground, P. euphratica generates the sprouts which are difficult to keep on growing after coming out of the ground, leading to the phenomena that a large amount of seedlings generated on the roots but only a small amount of them could be alive in the future.更多还原