基于MODIS数据的延安市近20年植被时空动态研究

Spatial and temporal dynamic change of vegetation in Yan’an City in recent 20 years based on MODIS data

基于MOD13A1数据,分析延安市近20年植被时空动态变化特征,探明影响植被指数变化的因素。利用最大值合成法获取延安市各年NDVI空间分布图,通过趋势线分析法获取植被指数的动态变化,结合气象数据分析降水与气温对植被指数的影响。结果表明:延安市2000~2019年植被指数在0.54~0.75之间,其空间分布呈现南高北低的特征,与延安市土地利用类型分布相符,在时间分布上,呈现显著上升趋势,整体上升速率为0.095/10 a;2000~2019年,延安市79.83%的区域植被呈改善的趋势,主要分布在延安市北部和东部的黄土梁峁、沟壑区,退化的区域占延安市的0.34%,主要分布在延安市城区及县级城市的城郊区域,呈点状和条带状分布;2000~2012年,人类活动是决定植被指数状况的主导因素,2013~2019年影响延安植被生长的主要因素是水热条件。综上所述,延安市植被指数呈现上升趋势,国家政策退耕还林还草工程取得了巨大成就,改善了延安市整体的生态环境。

The analysis of spatial and temporal characteristics of vegetation in Yan’an City in recent 20 years based on MOD13 A1 data so as to find out the factors that affect the change of vegetation index. The maximum synthesis method is used to obtain the spatial distribution map of NDVI in Yan’an. The dynamic change of vegetation index is obtained by trend line analysis. Combined with meteorological data, the effects of precipitation and air temperature on vegetation index were analyzed. The results show that the vegetation index of Yan’an from 2000 to 2019 is between 0.54 and 0.75, and its spatial distribution is high in the south while low in the north, which is basically consistent with distribution the land use types in Yan’an City. This shows a significant upward trend in time distribution, and the overall rising rate is 0.095/(10 a). From 2000 to 2019, 79.83% of the regional vegetation in Yan’an City showed a trend of improvement, which was mainly distributed in the loess beam and gully regions in the north and east of Yan’an City, and the degraded areas accounted for 0.34% of Yan’an City. it is mainly distributed in the urban areas of Yan’an and the suburban areas of county-level cities, showing dotted and banded distribution. From 2000 to 2012, human activity is the main factor that determines the status of vegetation index, and the main factor affecting the growth of vegetation in Yan’an from 2013 to 2019 is hydrothermal conditions. To sum up, the vegetation index of Yan’an City shows an upward trend, and the national policy of returning farmland to forest and grassland project has made great achievements, which has improved the overall ecological environment of Yan’an City.