近20年宝鸡市植被覆盖度动态变化及驱动力分析

植被覆盖度是反映地区生态环境的重要指标,本文利用1988、2000、2007年三期TM遥感数据,计算出宝鸡市的归一化植被指数(NDVI),并通过像元二分模型计算出不同时段的植被覆盖度,最后将归一化植被指数的差值进行分级,以此来分析宝鸡市1988~2007近20年的植被覆盖变化动态。结果表明:1988~2000年间,极低覆盖度、高覆盖度、极高覆盖度比例都呈现出减少趋势,减少比例分别为宝鸡市土地面积的0.02%、1.66%和1.98%,其他各级别植被覆盖度也都有不同程度下降;2000~2007年间,极高植被覆盖度增大的比例达到8.04%。NDVI差值指数分级结果显示,1988~2000年植被退化明显,2000~2007年有大幅度改善;从长时间序列看,生态退化比较明显的区域是金台区、扶风县、岐山县、凤翔县。人为因素是影响植被覆盖变化的主要驱动因素,主要包括山区或平原区的生态绿化工程、城市景观绿化工程、农业产业结构调整、畜牧业发展、人口因素等。

Dynamic Change and Driving Force Analysis of Vegetation Coverage in Baoji City in Recent 20 Years

The vegetation coverage is an important indicator of the ecological environment in one region. In this paper, using TM remote sensing data in 1988, 2000 and 2007, the normalized difference vegetation index （NDVI） of Baoji was calculated. And the vegetation coverage of Baoji in different times was worked out through the pixel binary model. Finally, the difference of normalized difference vegetation index was classified to analyze the dynamic change of vegetation coverage in Baoji in the past 20 years from 1988 to 2007. The resuits showed that the extremely low coverage, high coverage and extremely high coverage all showed a decrease trend from 1988 to 2000, and the reduce proportion was 0.02%, 1.66% and 1.98% of Baoji land area re- spectively. The other levels of vegetation coverage also had different degrees of decline. The proportion of ex- tremely high vegetation coverage increased 8.04% from 2000 to 2007. NDVI difference value grading results showed that the vegetation degradation from 1988 to 2000 was serious, while the situation was improved during 2000 -2007. From long time series, the vegetation degradation mainly appeared in Jintai District, Fufeng County, Qishan County and Fengxiang County. Human factors were the main driving force that affecting the change of vegetation coverage, mainly including the ecological greening projects in mountains or plains, urban landscape greening projects, agricultural industrial structure adjustment, animal husbandry development, demographic factors, etc.