雅鲁藏布江源区风沙化土地演变趋势

雅鲁藏布江源区是世界上最高的江河源,其生态功能状况直接影响其水源涵养功能以及中下游地区,特别是日喀则和拉萨等地区的生态安全。源区内土壤发育程度低,气候干旱多风、植被稀疏,风沙地貌发育。论文以雅鲁藏布江源区所在的马泉河流域为研究对象,借助RS和GIS技术,解译了1990年、2000年和2008年3期近20 a遥感影像,并结合DEM数据,分析风沙化土地的分布特征及演变趋势,对准确把握源区内风沙化土地现状及发展趋势具有重要意义。研究结果表明:①2008年,源区共有风沙化土地1 376.22 km2,其中,固定沙地占风沙地总面积的36.03%,半固定沙地占28.10%,流动沙地占9.39%,裸露砂砾地和半裸露砂砾地分别占14.64%和11.84%;②源区风沙化土地呈逐年递增趋势,其中,1990年为1 281.78km2,2000年为1 359.7km2,2008年为1 376.22km2,近20 a增加了94.44 km2;③从高程上看,分布在海拔4 600~4 800 m范围内的风沙化土地占风沙地总面积的76.13%;从坡向上看,分布在平坦地区的风沙化土地占风沙地总面积的56.97%,其次为西南坡和南坡,比例分别为11.20%和8.66%。

Traits and Dynamic Changes of the Aeolian Sandy Land in the Source Region of the Yarlung Zangbo River in Tibet

The source region of the Yarlung Zangbo River originating from the Chamyungdung glacier on the northern slope of the Himalayas is one of the highest river sources in the world. Its ecological and environmental quality plays an important role in the water conservation function and the ecological security of downstream areas, such as the cities of Shigatse and Lhasa. The aeolian sandy land has developed obviously, as the climate is dry, the soil is poor and the environment is fragile in this region. This paper analyzed the distribution characteristics of aeolian sandy land and its dynamics change in the source region of the Yarlung Zangbo River by interpreting the past 20 years’ Remote Sensing (RS) images of three periods, that is, 1990, 2000 and 2008, and matching it with the DEM data of this region using the technique of RS and GIS technology. The purpose is to illustrate the current situations correctly and find out the evolution tendency of the aeolian sandy land in the source region of the Yarlung Zangbo River. It was shown that: 1)The area of aeolian sandy land in the source region of the Yarlung Zangbo River was 1376.22 km² in 2008, including fixed sandy land which accounted for 36.03%, semi-fixed sandy land which accounted for 28.10%, shifting sandy land which accounted for 9.39%, bare gravel sandy land which accounted for 14.64% and semi-bare gravel sandy land which accounted for 11.84%. 2)The area of aeolian sandy land in the source region of the Yarlung Zangbo River was 1281.78 km² in 1990, 1359.7 km² in 2000 and 1376.22 km² in 2008 respectively. It had increased by 94.44 km² in the nearly 20 years. 3)The aeolian sandy land was mainly distributed at the elevation ranging from 4600 m to 4800 m, or 76.13% of the total. From the view of the aspect, the aeolian sandy land was mainly distributed in the flat area, or 56.97% of the total sandy land, following by the southwest aspect and south aspect, being 11.20% and 8.66% respectively. 4) Abundant sand materials and strong wind blowing are the potential conditions for aeolian sandy land development. The global climate has been getting warmer in the past 20 years, and the higher temperature favored to the further development of aeolian sandy land in the study area.