塔里木河下游植物群落分布格局及其环境解释

研究表明,塔里木河下游地区共有植物18种,分别隶属于9科、15属。其中藜科(Chenopodiaceae)、柽柳科(Tamaricaceae)、豆科(Leguminosae)3个科有10种,约占所有种数的56%,反映了干旱区旱生耐盐种类占优势的特点。样地排序结果表明,沿样地CA第一排序轴,所有18个调查样地可划分为3种类型,分别对应3种不同地下水位,即浅地下水位区(<3m)、中地下水位区(3~5m)和深地下水位区(>5m),不同的植被类型组合亦分别对应不同类型的地下水位。CCA排序表明,影响该地区植物群落分布格局的环境因子主要是地下水位、土壤含水量、土壤pH值。CCA排序分析可将18种植物分为4个组,分别对应于不同的环境因子变化梯度。从管理的角度出发,在塔里木河流域下游地区进行受损生态系统的恢复与重建过程中,要重点考虑到上述提及的主要环境因子,尤其是重视水资源的合理开发与利用,采用适宜的灌溉方式,防止地下水位下降和土壤盐渍化的发生。

Plant Communities and Their Interrelations with Environmental Factors in the Lower Reaches of Tarim River

The distributive pattern and abundance of desert plant communities were examined in the lower reaches of Tarim river, southern Xinjiang. Eighteen species were collected within 18 sites along a sequence of groundwater tables in six transects. Except for Tamarix ramosissima and Populus euphratica, which were almost distributed across all sites, most of investigated species had low occurrence frequency in quadrats. Corresponce Ordination of a reduced dataset of 18 species revealed a separation of taxa into distinct groups corresponding to the different tables of groundwater. Clearly defined groups of species were strongly associated with three types of groundwater zones: shallow groundwater zones, intermediate groundwater zones and deep groundwater zones, ranging from <3 m, 3-5 m to >m respectively. Four distinctive taxa groups are identified corresponding to the three zones of groundwater table and the several major environmental factors. Canonical Correspondence Analysis (CCA) of the 18 species and seven environmental variables revealed that the most important factors associated with the distribution of species were groundwater table, soil moisture and soil pH value in the lower reaches of Tarim River. From a management standpoint, there is no reason to doubt that the most important factor for restoration of damaged ecosystem in this region is reasonable use of water resources in the whole Tarim river valley, especially in the middle and upper reaches of the river. This study confirms that the planners and managers of nature reserve in this area should take these major environmental factors and species characteristics into account in the process of decision-making.