我国从东北到西北长约4500km的大部分沙区为山地所环绕,山地阻挡了水汽的输入,大部分降水在山地迎风坡降落,而沙漠中年降水量只有200～300mm,西北沙漠中心地带年降水量只有几十毫米甚至十几毫米。但山地截留的降水又源源不断地输入沙漠而形成片片绿洲。山地成为绿洲主要的水源供给地。水是绿洲的命脉,无水即无农业,而山地可称得上是绿洲的“命根”了。从山地到绿洲之间有一个植被稀少的荒漠地带,成为山地到绿洲之间的缓冲带。从宏观、整体、综合的角度,将山地、沙漠(戈壁)、绿洲看成一个庞大的生态系统,它们是相互依存、相互关联、又相互制约的。必须从宏观的角度,处理好它们之间的关系,才能使这个庞大的生态系统趋向稳定和巩固,走向良性循环,使绿洲农业得以持续发展。

The desert areas of China,a stretch of about 4500km from northeastern to north wes-tern China,are surrounded by mountains.Mountains retard the incoming vapor in the atmo sphere and the most parts of precipitation fall on the windward side.The annual precipitation in the in-terior of desert account s for only200～300mm.The annual totals in Northwest deserts account for several tens,even as less as ten to twenty.But on the mountain slopes there are much more precipitation,and the water continuously goes into the deserts so that some oases form.Hence mountains are the main water supplies of oases.No water,no agriculture.Mountains can be con-sidered as the life roots of oases.From mountains to oases are the deserts with very less vegeta-tion which can be taken as the buffer zones.As viewing the situation as a whole and compre-hensively,we can take the mountains,deserts(gobis)and the oases as a big ecological system.We must manage well their relationships so as to enhance this big ecological system to be stable and strengthened and be maintained in a sound cycle so that the agriculture in oases is kept sus-tainable.