中文摘要：

采用根系质量、密度、消弱系数和表面积等指标对塔里木河下游主要建群种胡杨根系空间分布特征进行定量研究,并分析了胡杨根系分布与土壤含水率的关系,为塔里木河下游受损天然胡杨林恢复提供依据。研究表明：（1）细根分布频数占活根总数的比例最大,死根所占比例从表层到深层有逐渐递减的趋势。（2）单株胡杨根系密度分布不对称。随着水平距离的增加,细根根系长度呈现近长远短的特点,而根量的水平分布呈现近重远轻的特点,主要集中在100～200 cm范围内。（3）胡杨根系垂直分层明显,根量在垂直方向上呈两头小、中间大的梭形分布,根系消弱系数值较大。（4）在土层30～120 cm范围内,细根表面积分布与土壤含水率分布呈显著正相关。

英文摘要：

Based on the indices of root weight,density and surface area,we analyzes spatial distribution characteristics of root system of Populus euphratica in the Algan transection of the lower Tarim River.The relationship between root system spatial distribution and soil moisture is also discussed.The results can provid a scientific basis for restoring the destroyed P.euphratica forest in the lower reaches of Tarim River.The results showed that：（1）the fine roots（D≤2 mm） is the most among distribution frequency of different diameter roots.The proportion of dead roots gradually decreasing with increasing the soil depth;（2）The root system of one sample tree is distributed stochastically in horizontal space.With the increase of the horizontal distance,the length of fine roots has a deceasing trend.The root weight is also declining,which is distributed mostly in soil depth of 100～200 cm;（3）The root system of P.euphratica is distributed significantly in vertical direction.The root weight shows a pattern of a few in each end and many in the middle of soil stratification.The root extinction coefficient of P.euphratica is higher in most soil depth;（4）There is a positive autocorrelation between surface area of root system and soil moisture content in a scope of 30～120 cm soil depth.