近20a来新疆植被覆盖变化特征研究

Study on the Change of Vegetation Coverage in Xinjiang since Recent 20 Years

以前人提取的近20 a(1982-2000年)植被覆盖度指数FVC为基础数据,根据新疆不同的自然地理区域和地貌类型,采用分区海拔的方法对FVC影像进行分类。对各地理区域植被的变化采用距平处理,初步定量分析了新疆植被的变化状况。结果表明,近20 a来新疆无论是山地还是平原,高植被覆盖度的绿洲和森林面积均有所增加。以地区论,伊犁地区植被覆盖变化幅度最小,状况最为稳定;东疆地区绿洲与高覆盖度植被稳定,低覆盖度植被变化幅度相对较大;北疆平原地区绿洲面积增加,高覆盖度植被和无植被区面积减少;北疆山地森林植被增加,不同时间增加的速率不同,高覆盖度植被与森林的变化呈一定的相互转换关系;南疆地区绿洲面积显著增加,与此相对应的是高、中覆盖度草地的面积下降,山地荒漠面积近年来有所增加,森林和高覆盖度草地面积也有所增加。从植被类型转换方式来看,在平原区,绿洲与中、高覆盖度草地面积之间具有强烈负相关;而山区的植被类型转换多发生在无植被区与低、中覆盖度草地之间或高覆盖度草地和森林之间。人工绿洲面积的变化成为新疆平原区植被类型变化的重要因素,南北疆绿洲面积增加的同时,中、高覆盖度植被减少,即绿洲与沙漠之间过渡带的植被面积减少。

In this paper, the images of vegetation coverage indexes (VCI) are classified base on the YCIs de rived by some scientists in successive 20 years, different geographical subregions and morphological types in Xin jiang, the anomalies of the vegetation change in all the geographical subregions are processed, and the vegetation change in Xinjiang is quantitatively analyzed. The results show that the areas of the oases and forests with high vegetation coverage have been enlarged whether in the mountainous regions or plains in Xinjiang since recent 20 years. The change amplitude of vegetation coverage in the Yili region is the lowest, and the vegetation coverage is the most stable; in east Xinjiang, the vegetation coverage is stable in the oases with high vegetation coverage but changes obviously in the regions with low vegetation coverage; in north Xinjiang, the areas of the plain oases and mountainous forests are enlarged, the areas of the regions with high vegetation coverage and of the vegeta tion-uncovered regions are reduced, and there is a certain mutual conversion between the areas of regions with high vegetation coverage and the forests; in south Xinjiang, the area of the oases is obviously enlarged, but the area of grasslands with high and moderate vegetation coverage is reduced, and the areas of the mountainous deserts and the forests and grasslands with high vegetation coverage are enlarged to some extent Viewing from the conversion ways of the different vegetation types in the plains, there is a strong negative correlation between the areas of the oases and the grasslands with moderate and high vegetation coverage; the conversion of vegetation types occurs mostly between the vegetation-uncovered regions and the regions with low and moderate vegetation coverage or between the grasslands and the forests with high vegetation coverage. The change of area of the artificial oases becomes as an important factor resulting in the change of vegetation types in the plains in Xinjiang. While enlarging the area of the oases in both south Xinjiang and north Xinjiang, the area of the regions with moderate and high vegetation coverage is reduced, that is the area of the ecotones between the oases and deserts is reduced.