山西省不同生态分区增强型植被指数(EVI)对气候因子的响应

利用2000—2014年MODIS EVI数据、27个气象站点逐月气温和降雨量、MOD16蒸散量数据,分析了山西省15年来的植被覆盖变化及其对气温、降水和蒸散量的响应特征。结果表明:(1)山西省植被总体呈现上升趋势,增速为2.6%·10a~(-1),不同生态分区中Ⅱ东部大行山山地Ⅲ中部盆地Ⅳ西部山地Ⅰ晋北山地Ⅴ晋西黄土丘陵区。(2)山西省植被覆盖具有较大的区域差异,其中东南部的EVI明显高于西北部,EVI频度图呈现"单峰结构",全省绝大部分地区呈现不变或增加趋势,显著面积比例为25.95%,严重退化面积比例为1.04%。(3)基于年尺度的EVI与降水、蒸散量呈正相关,与温度负相关,基于月尺度的EVI与气温、蒸散量呈显著正相关,蒸散量与EVI的相关性好于降水、温度单一因子,而降雨量对EVI变化存在一个阈值。(4)从生长季考虑,从春季到夏季各大生态区蒸散量与EVI均为正相关并且逐渐加强,秋季除Ⅲ中部盆地外其它自然区均为负相关。

Response of enhanced vegetation index (EVI) to climatic factors in different ecological division of Shanxi Province

Using the data of MODIS EVI,monthly mean air temperature and precipitation from 27 weather stations and transpiration from MOD16 during 2000 to 2014,analyzed the vegetation cover change in recent 15 years in Shanxi Province and its response feature to temperature,precipitation and evapotranspiration.The result showed that:(1) Overall the vegetation cover showed an upward trend,the increasing speed was 2.6 ％· 10a-1.In the different ecological division,the eastern mountain area Ⅱ ＞ the central basin Ⅲ ＞ the western mountain area Ⅳ ＞ the north Shanxi mountain area Ⅰ ＞ the west Shanxi loess Ⅴ.(2) The vegetation cover in Shanxi Province possessed rather large regional difference.Among them and the EVI in southeast part was obvious higher than the northwest part.The EVI frequency chart was appeared "unimodal structure".The most parts of province was showed unchange or increasing trend,the notable area ratio was 25.95 ％ and the degradation area ratio was 1.04 ％.(3) The yearly EVI with the precipitation and evapotranspiration was assumed positive correlation,negative correlation with the temperature,The monthly EVI with the temperature and evapotranspiration was showed significantly positive correlation.The correlation between evapotranspiration and EVI was better than the single factor as precipitation and temperature.Also the precipitation with EVI change was existed a threshold value.(4) From growing season considered the evapotranspiration with EVI,we can known that from spring to summer each big ecological region total showed positive correlation and strengthened gradually.In autumn,all other natural areas were negative correlation except the middle part of the central basin Ⅲ.