农牧交错区植被覆盖度动态变化遥感监测--以宁夏盐池为例

基于植被指数(NDVI)和植被覆盖度像元分解模型,建立了TM影像尺度下的盐池县植被覆盖度遥感定量模型,在此基础上研究了盐池县1989年和2003年2个时期植被覆盖度的动态变化.结果表明:盐池县2003年低覆盖度植被明显减少,较1989年减少了1 412.52 km2,中等植被盖度较1989年明显增加,为4 672.46 km2.中等植被覆盖度、高植被覆盖度在全县比例均有不同程度的增加.研究期间,植被覆盖等级未变化面积为3 692.32 km2,主要由中等植被覆盖度构成.植被退化面积为608.61 km2,而植被恢复面积达到3 310.13 km2,是退化面积的5.4倍.并进一步分析了植被覆盖度变化的原因.

RS Monitoring on the Dynamic Change of Vegetation Coverage in a Farming-pasturing Ecotone--A Case Study in Yanchi County, Ningxia Hui Autonomous Region

Vegetation coverage is an important index to measure land covers, and it is regarded as an important input parameter in evaluating land desertification, monitoring water loss and soil erosion, and developing the distributed hydrological model. In the process of land desertification, the dynamic change of vegetation factors, such as the vegetation coverage and biomass, are the main factors reflecting the vegetation productivity, and also the main factors indicating land desertification development or reversion. In this paper, a model of quantitatively monitoring the vegetation coverage at TM image scale in Yanchi County is developed based on NDVI and vegetation coverage pixel decomposed model, on which the dynamic change of vegetation coverage in the county in 1989 and 2003 is researched. The results show that the area with low vegetation coverage in 2003 was significantly reduced than that in 1989, and it was reduced by 1 412.52 km^2 ; the area with moderate vegetation coverage in 2003 was significantly enlarged than that in 1989, and it was enlarged by 4 672.46 km^2. The proportions of the areas with moderate and high vegetation coverage were increased in varying degrees. During the research period, the area of the regions of vegetation type without change was 3 692.32 km^2, which occupied 48.5% of the total area and was mainly composed of the regions with moderate vegetation coverage. The area of the regions where the vegetation was degenerated was 608.61 km^2, and the area of the regions where the vegetation was regenerated was 3 310.13 km^2, and it was 5.4 times of that where the vegetation was degenerated. All these reveal that the vegetation coverage in the study area is currently increased. The causes resulting in the change of vegetation coverage in the study area are analyzed.