额济纳绿洲近20年来土地覆被变化

土地利用/土地覆被变化研究是近年来全球环境变化研究的焦点之一。根据黑河下游额济纳绿洲土地生态分类，利用1982年与2000年2期TM遥感数据对比和野外实地调查，采用景观生态空间分布格局分析方法，分为河岸乔木林、河岸灌草林、荒漠稀疏灌丛、荒漠稀疏草地、河道与水域、盐碱化土地、城镇、戈壁、流动沙丘和剥蚀地山丘陵, 从各类土地分布面积变化和类型转移趋向与幅度两个方面，分析了额济纳绿洲20年来土地覆被变化。结果表明：①土地覆被类型结构发生了较大变化，河岸乔木林面积萎缩了0.97％、斑块数减小了376，而河岸灌草林增加了0.92％，数量减小1 316；而％LAND指数荒漠稀疏灌丛由4.49％增加到5.65％，由于中游来水量的锐减，河道和水域的斑块数由40个减少到6个，％LAND指数减小了0.15％。与此同时流动沙丘％LAND指数增加了0.42％。②近20年来以胡杨为主的河岸乔木林和荒漠稀疏草地减小了45.02％和14.55％，相应地以柽柳为主的河岸稀疏灌草地和荒漠稀疏灌丛增加了35.03％和25.88％；河岸乔灌林向河岸灌草林景观转移概率为45.95％，向荒漠稀疏灌丛和稀疏草地转移了0.78%和3.01％，向戈壁转移了10.87%；河岸灌草林景观类型向河岸乔灌林转移8.06％，向稀疏灌丛和稀疏草地转移10.95%和19.64%，向戈壁转移11.88％；③额济纳绿洲具有从河岸乔木→河岸灌草地→荒漠稀疏灌丛快速演化的趋势。

THE CHANGE OF LAND COVER/LAND USE IN EJINA OASIS OVER 20 YEARS

Land use and land cover change have been of great concern in global change study in recent years. Base on comparison with the remote sensing data in 1982 and 2000 and field investigation, the results of land cover and land use change were obtained by the method of landscape analysis. Ten types of land use were identified: riparian woods, riparian shrubbery, desert shrubbery, desert grassland, river-way and water area, salinised land, town, Gobi, shift sand dune, denudative upland. The results show that, (1) there were obvious changes in land cover structure. The area of riparian woods decreased 0.97% and the number of patch decreased 376; the area of riparian shrubbery decreased 0.92% and the number of patch decreased 1316. Meanwhile, the index of %LAND of desert shrubbery increased from 4.49% to 5.65%; Because of decrease of water quantity of discharge from middle reach. The patch of riverway and water area decreased from 40 to 6. the index of %LAND decreased 0.15%. At the same time, the index of %LAND of shift sand dune increase 0.42%. (2) the areas of riparian woods dominated by Populus euphratica and desert grassland decrease to 45.02% and 14.55%. However, the areas of riparian shrubbery dominated by Tamarix Spp and desert shrubbery increase to 35.03% and 25.88%. The transition probability is 45.95% from riparian woods to riparian shrubbery. At the same time, they are 0.78% and 3.01% from riparian woods to desert shrubbery and desert grassland. The succession trend of ecosystem was obtained: riparian woods→ riparian shrubbery and grassland→desert grassland. Meanwhile, the succession velocity becomes higher and higher.