2000—2015年乌兰察布市生长季NDVI时空变化及其影响因素

Spatiotemporal Variation of NDVI and Its Affecting Factors in Ulanqab City in Growing Season from 2000 to 2015

以2000-2015年MODIS中国500M NDVI月合成产品数据为基础,结合乌兰察布市同期降水和气温数据,采用趋势线分析法、差值法、复直线回归分析法和残差法等,对乌兰察布市近16 a来生长季归一化植被指数(NDVI)进行像元尺度的时空变化及影响因素分析。结果表明:①2000-2015年乌兰察布市NDVI介于0.354~0.555,整体呈波动上升趋势,空间分布差异明显,且呈东南高西北低的特点;②2000-2004年、2005-2009年、2010-2015年乌兰察布市植被覆盖变化类型呈改善→退化→改善。植被覆盖改善较退化的速度慢,且植被退化后恢复缓慢;③乌兰察布市植物生长受降水、气温的双重影响。NDVI与年均降水量呈显著正相关(r=0.730,P=0.001),并通过了0.01显著性水平检验,与气温呈负相关(r=-0.351,P=0.182),二者相关关系不显著,相较气温而言,降水是影响植物生长的主要气候因子。在排除人类活动的影响下,降水和气温对乌兰察布市NDVI的贡献自西北向东南由0.213逐渐增加至0.805;④人类活动对植被指数起消减作用的区域占研究区总面积的55.92%,对植被指数起积极作用的区域占研究区面积的44.08%。

In this paper,the spatiotemporal change of the Normalized Difference Vegetation Index(NDVI)and its affecting factors in Ulanchab City in recent 16 years were analyzed.The study was based on the monthly synthetic product data of MODIS China 500 M NDVI from 2000 to 2015 and the precipitation and temperature data in the same period.The trend line analysis,differential method,complex linear regression analysis and residual method were used.The results showed that:①The vegetation NDVI in Ulanqab City varied in a range of 0.354-0.555 during the period of 2000-2015,and the overall trend fluctuated and its spatial distribution was obvious.It was high in the southeast but low in the northwest;②The vegetation types in Ulanqab City were in a trend of improvement→degeneration→improvement during the periods of 2000-2004,2005-2009 and 2010-2015,and the degenerated vegetation was regenerated slowly;③Vegetation growth in Ulanqab City was affected by both precipitation and temperature.There was a significantly positive correlation between the NDVI and the annual precipitation(r=0.730,P=0.001),which passed the significance test at 0.01 level,but a negative one between the NDVI and the temperature(r=-0.351,P=0.182),and the correlation between the two climatic factors was not significant.Without considering the influence of human activities,the contribution of precipitation and temperature to vegetation NDVI was gradually increased from 0.213 to 0.805 from the northwest to the southeast;④The areas where human activities played a role in reducing vegetation index and increasing it accounted for 55.92%and 44.08%of the total study area respectively.