基于扰动指数的天水南部植被扰动时空序列研究

Study on spatio-temporal variation of vegetation disturbance in the southern part of Tianshui by disturbance index

利用全球扰动指数(The MODIS Global Disturbance Index, MGDI)模型并以长时间序列的MODIS的增强型植被指数(Enhanced Vegetation Index,EVI)和地表温度(Land Surface Temperature,LST)数据作为数据源对天水南部地区2001—2016年植被扰动指数时空分布变化特征和驱动因子进行研究。结果表明:(1)16年来植被扰动指数的均值空间分布不均,其值分布于0.66—1.09之间,天水市南部地区的西北和西部部分地区植被扰动指数明显低于其它地区,且主要为积极扰动。(2)植被扰动指数的年际变化呈降低趋势,占总面积的89.58%,其中研究区中农耕区减小的趋势最为明显。植被扰动指数的变异系数分析结果表明, 2001—2016年以来天水南部大部分地区植被扰动指数变化较稳定。其中,西北部的农耕区扰动指数波动幅度较大,而林区波动相对较小。(3)植被扰动情况受海拔和坡度、河流和道路的影响。空间分布上,扰动主要发生在海拔相对较高、坡度较缓及近河流和道路地区。

The study investigated the temporal-spatial distribution characteristics and driving factors of vegetation disturbance index in the southern part of Tianshui from 2001 to 2016 based on MGDI model,using the Enhanced Vegetation Index(EVI)and Land Surface Temperature(LST)in long time series as data sources.The results are as follows.(1)The spatial variation range of mean vegetation disturbance index value was 0.66-1.09 mm on the grid during 2001-2016,which had a significant difference in spatial patterns.And the vegetation disturbance index of the northwest and western parts of the study area was obviously lower than that of other areas,and mainly for positive disturbance.(2)The interannual variability of vegetation disturbance index was decreasing,accounting for 89.58%of the total area.Among all the study area,the reducing trend was most obvious in the cultivated area.The analysis of variance coefficient of vegetation disturbance index showed that the change of vegetation disturbance index in most parts of southern Tianshui since 2001-2016 was relatively stable while the disturbance index of the farming area in the northwest was larger,and the forest area fluctuated less.(3)Vegetation disturbances were affected mainly by altitude,slope,river,and road.Judging from spatial distribution,the disturbance occurred mainly at relatively low elevations,with slower slopes and near rivers and roads.