近17年陕西榆林植被指数的时空变化及影响因素

植被指数是研究区域植被变化的重要手段。基于MODIS/Terra NDVI遥感影像数据,对陕西榆林市2000—2016年8月份NDVI进行像元尺度的时空变化及影响因素分析。结果表明,榆林有96.44%的区域植被指数是增加的,增加值在0—0.02/a区域面积占榆林的93.63%,呈显著增加趋势的面积占榆林的80.72%。复直线回归分析显示,气象因素对植被生长、演化起到了促进作用,人类活动使得植被指数等级变得更加均匀。人类活动抑制植被生长演化的区域占榆林总面积的45.04%,主要分布在榆林市最北部的府谷县、榆林市南部及西部的大部分区域;人类活动促使植被指数增加的区域占榆林总面积的54.96%,说明有一半以上的区域,人类活动对植被生长起到了促进作用,这些地区的封山育林、退耕还林、退牧还草等措施的实施效果较好。

Analysis of the spatial-temporal change and impact factors of the vegetation index in Yulin, Shaanxi Province, in the last 17 years

Vegetation index is an important method to study regional vegetation changes. The present study is based on MODIS/Terra NDVI remote sensing data, and analyzes the spatial-temporal changes and impact factors of the NDVI in August from 2000 to 2016 at pixel scale in Yulin City of Shaanxi Province. The results showed that vegetation index increased in approximately 96.44% of the land area in the Yulin city, and the area with increasing NDVI between 0-0.02/a accounts for 93.63% of the land area of Yulin city. The area with significant increasing trend accounts for 80.72%. The complex linear regression analysis showed that meteorological factors play a positive role in the growth and evolution of vegetation, and human activities also make the vegetation index to become more uniform. The area where the human activities restrain the growth and evolution of the vegetation covers 45.04% of area of Yulin. It is mainly distributed in Fugu County, which is located to the north of Yulin and most areas of the southern and western parts of Yulin. The area where human activities promote the increase of the vegetation index accounted for 54.96% of area of Yulin, which indicated that in more than half of the region, human activities have played a positive role in the growth of vegetation. In these areas, the effects of forest conservation, returning farmland to forests, and returning pasturage to natural grassland are greater than those in other areas.