西藏“一江两河”流域中部地区沙漠化土地类型及其分布规律

TYPES AND DISTRIBUTIVE REGULATION OF DESERTIFIED LANDS IN THE MIDDLE KEACHES OF YALUTANGPO RIVEK,TIBET

西藏“一江两河”中部流域地区是我国青藏高原高寒区的一部分，存在着诸多环境问题，其中以土地沙漠化问题最为突出，要保护和改善其生态环境，首先要防治土地沙漠化。在实地考察及沙漠化图件编制工作基础上，本文对沙漠化土地指征确立、类型划分及分布规律进行了较为系统的阐述。根据对本区各种类型沙漠化土地量测的结果，沙漠化土地总面积１８６０．９ｋｍ￣２，按沙漠化发展程度，本区可划分轻度、中度、严重沙漠化土地，面积分别为５３０．５ｋｍ￣２，７５２．８ｋｍ￣２，５７８．６ｋｍ￣２。根据地表物质组成的不同，本区可划分为砂质和砂砾质沙漠化土地，面积分别为９１６．４ｋｍ￣２和９４４．５ｋｍ￣２。从分布规律看，沙漠化土地主要分布在河谷地区，尤以雅鲁藏布江宽谷段的面积分布最大，并从河谷的江心洲延续至山前冲洪积扇及山坡等不同地貌单元上。同时，文章对本区非沙漠化土地及潜在沙漠化土地问题作了必要的说明。

The middle reaches region of Yalutangpo River in Tibet is a part of high-frigid areasof Qinghai-Xizang Plateau,There are many environmental problems of which the landimproving the ecological environment,the desertification control is first thing of all. Throug h the field investigation and the maps of compilled for desertified lands.The paperdisscuess that the classification of desertification degrees and their indicators anddistributive regulatiOn,Based on the results of measuring all k inds types of desertifiedlands.The total area of desertified lands is 1860.9 sq kili metres.According to the degreeof desertiflcation,we divide desertified lands into slight、medinte、severe three types.Theareas of the types are respectively 530.5km￣2,752. 8km￣2,578. 6km￣2. According to the landsurface texture,the desertified lands can be divided into sandy and sandy-gravels,theareas of the two types are respectively 916.4km￣2 , 944.5km￣2.In the respect,the desertifiedlands are mainly in valleys,especially in the wide-valleys of Yalutangpo River. It alsoextends from valley beach to the piedment fiuvial fan and hillside. The paper also explainsnecessarily the problems of non-desertified lands and latent desertification lands.