中文摘要：

以因不合理的水土资源开发而出现严重生态退化的典型区——塔里木河下游为研究区，通过在塔里木河下游开展的土壤种子库实验，分析了塔里木河下游土壤种子库的基本特征和种子库密度、物种组成上的季节差异，并从土壤种子库的角度探讨了塔里木河下游生态恢复的可行性。（1）塔里木河下游土壤种子库的季节差异较大，如果排除放牧的影响，3月份土壤种子库的密度和物种丰富度总体上要小于8月份的土壤种子库；（2）从物种组成上看，3月份物种组成以一年生草本占优势，而胡杨和柽柳的种子基本上都出现在8月份的土壤种子库中；（3）随塔里木河下游地上植被群落退化程度的加重，种子库的密度和物种数均呈现明显的下降趋势；（4）鉴于土壤种子库无论在物种还是密度上均要远丰富于地上植被群落的事实，认为通过激活土壤种子库来实现下游生态的局部恢复在理论上是可行的。考虑到主要建群植物的生态恢复，建议今后的输水时间应该选择在8月到11月之间。

英文摘要：

The typical severely degraded regions due to irrational utilization of water and land in the lower reaches of Tarim River were chosen as a study area. By using the germination method in the experiment on germination of soil seed bank, the dynamics of basic characteristics, density, and species of soil seed bank were analyzed. Vegetation restoration in the areas was also discussed in terms of potential role of the soil seed bank. Results show that without taking the effect of graze into account, seasonal dynamics of the soil seed bank is quite obvious and density and species abundance of the seed bank in March is lower than that in August. In terms of species composition, annual herbaceous plant is dominant in March and the seeds of Populus euphratica Oliv and Tarnarix L almost appear in August. With the aggravated degradation, density and species abundance of the soil seed bank decrease significantly. To activate the soil seed bank is feasible theoretically for vegetation restoration in the lower reaches of Tarim River, for density and species abundance of soil seed bank is further larger than those of standing vegetation. Taking account of vegetation restoration and regeneration, our study suggests that the best time for water transferring should be from August to November.