青藏公路与铁路沿途1981年～2001年植被覆盖变化

Vegetation Change along the Qinghai-Xizang Highway and Railway from 1981 to 2001

在青藏公路与铁路沿途区域,利用1981年至2001年的8km分辨率PathfinderNOAA/NDVI数据,基于每个象元变化的年植被峰值计算进行了像元水平的线性趋势分析,并运用地理信息系统(GIS)软件研究了区域植被覆盖的空间分布和动态变化特征。主要结论:①在研究区内,反映植被覆盖的NDVI值在空间上呈现出两端高中间低的态势,依次是农作区和森林区>高寒草甸>高寒草原>荒漠草原;②20年间,研究区植被覆盖程度变化总体趋于稳定,覆盖程度呈减少趋势的区域明显高于增加的区域,植被覆盖程度增减因区域而异;植被覆盖程度增加和显著减少地区主要分布在农作区和高寒草甸区,轻微减少地区主要分布在高寒草原和荒漠草原区;③植被覆盖变化程度在拉萨河谷地、湟水谷地和黄河流域等人类活动比较频繁的区域增减趋势比较明显;而在可可西里地区等人类活动比较少的区域变化轻微。

In this article, spatial distribution and dynamic change of vegetation cover along Qinghai-Tibet highway and railway were studied using NOAA AVHRR-NDVI monthly data from 1981 to 2001. By analyzing the data, we found that the NDVI value in July, August and September are rather higher among a year, and obtained a linear trend by calculating NDVI of each pixel which was computed through average value of NDVI in July, August and September. The map showed the spatial and relative changes of NDVI in each pixel by means of GIS. The results are as follows： 1） Vegetation cover of the research area by NDVI tends to be high at the two ends of the area and low in the middle, and agriculture area 〉 alpine meadow 〉 alpine grassland 〉 desert grassland;2）In the research area, the area of high increase, slight increase, no change, slight decrease and high decrease are 0.29 %, 14.86%, 67.61%, 16.7 % and 0.57 % of the whole region. The increase and high decrease of vegetation cover pixels distribute in the agriculture and alpine meadow, light decrease pixels distribute in the alpine grassland and desert grassland;3）In the area where human being live, the trend of change is obvious, such as the valleys of Lasha river and Huangshui river and area along the Yellow river; on the high altitude area with fewer people living in, the trend of change is relatively low, like the area of Kekexili;4）Human being＇s behaviors is a key factor followed by the climate changes affecting vegetation coverage.