1998-2018年藏北申扎县植被NDVI时空变化及其影响因素

为研究1998-2018年申扎县归一化植被指数（Normalized difference vegetation index，NDVI）的变化及其驱动力，本研究基于申扎县NDVI、地形和气象等数据，采用线性回归和残差分析等研究方法分析申扎县NDVI年际时空变化特征及其影响因子。结果表明：申扎县NDVI整体呈波动上升趋势，年均增长率为1.595%；年均NDVI随高程和坡度的增加呈现单峰曲线状的变化趋势，峰值分别位于4 900~5 200 m和10°~15°；NDVI与气温的正相关性（r=0.556，P=0.009）较降水（r=0.271，P=0.234）高；气温每升高1℃，NDVI增加0.291；降水量每增加100 mm，NDVI增加0.224；2012年后人类活动总体上开始对植被生长产生正作用；NDVI与人类活动成正、负显著相关的区域占比为24.13%，20.01%。总体上，NDVI增加主要是由于气候暖湿化和地方生态工程的有效实施等共同作用导致的。

Spatial-temporal variation of NDVI and its influencing factors in Xainza County from 1998 to 2018

This study was aimed to study the variation of vegetation NDVI (Normalized difference vegetation index) and its driving forces in Xainza County from 1998 to 2018. Based on NDVI,topographic and meteorological data,this study analyzed the interannual temporal and spatial variation characteristics of NDVI in Xainza County and its influencing factors by using linear regression and residual analysis and other methods. The results showed that:NDVI in Xainza county showed an upward trend of fluctuation with an average annual growth rate of 1.595%. The average annual NDVI showed a single peak curve trend with the increase of elevation and slope,with the peak value of 4 900~5 200 m and 10°~15°. The vegetation growth was positively correlated with precipitation and air temperature,and the correlation and significance with air temperature (r=0.556,P=0.009) was higher than that with precipitation (r=0.271,P=0.234). For every 1℃ increase in temperature,NDVI increased by 0.291,for every 100 mm increase in precipitation,NDVI increased by 0.224. After 2012,human activities had a positive impact on vegetation growth. On the whole,the increase of NDVI was mainly due to the combined effects of climate warming and humidity and the effective implementation of local ecological engineering.