长江上游生态建设取得了显著成绩，20世纪90年代森林覆盖率和地表植被覆盖度较60－70年代有了显著的提高，如四川盆地浅丘区森林覆盖率，60年代只有5％左右，到90年人后期达22．7％。虽然地表植被覆盖有了显著改善，但是生态退化问题仍比较严重，突出地表现在如下几方面：（1）森林生态系统的空间结构不合理，群落层片结构简单，人工林生态系统的林种，树种组成单一，低山丘陵区针叶化倾向日趋明显，其林下枯枝落叶层缺失，森林土壤层很薄，一般只有30－40cm，土壤最大持水能力一般为300－500m^3/hm^2，而该地区原始森林土壤可达2000－2500m^3/hm^2。（2）草地生态系统退化面积在扩大，如长江上游源头地区草地破坏引起的土地荒漠化面积达195万hm^2。（3）农田生态系统退化主要分布于生产与生态功能均不高的坡耕地，多数坡耕地水土流失比较严重，土壤侵蚀模数一般达2500－5000t/km^2·a，坡耕地耕作层浅薄，蓄水保水功能很弱。根据本区主要生态系统类型的退化现状与特点，在生态学理论的指导下，提出退化生态系统的恢复，重建与改建的对策和途径，为长江上游生态屏障的构建提供新的思路。

Great successes has been achieved in ecololigcal constuction on the upper reaches of the Changjiang River.The cover rate of forest and cover degree of vegetation in 1990's were obviously raised when compared with those in 1996's-1970's.For example,the avarege cover rate of forest in the Sichuan Basin was about 5% in 1960's,and was 22.7% in later 1990's.But problems of ecological degradation have also been serious,which included following aspects:①Space structures and community structures of forest ecosystems are unreasosnable;strucures of forest and free species of the artificial afforestation ecosystem are very simple;coniferous tress in the low mountain and hill areas have increased obviously;litters under the forest are very little,the forest soil layer is very thin with 30-40 cm;the maximum moisture capacity of thf forest soil is only 300-500m~3/hm~2 which is much lower than that of the original forest soil with 2500-3000m~3/hm~2.②Degraded area of grass lands are being enlarged,such as the grass land of Changjiang Rivers source are has seriously been disturbed,with deserted area of grass land keing 195×10~8 hm~2 .③Degradation of agricultural land is mainly occurred on slope cultivated land which is low in productivity and ecological function;Water and soil losses of most of slope cultivated land are serious,intensity of soil erosion is 2500-500t/km~2 ·a,cultivated horizon of the eroded cultivated land is very thin with very low moisture holding capacity.According to the degraded situation and features of the main ecosystem types and ecology theory,countermeasures for restoration and enhancement the degraded ecosystems are suggested,and new ides provided for ecological protective screen csontruction on the upper reaches of the Changjiang River