京津冀城市扩张对植被和地表城市热岛的影响

基于MODIS-LST、EVI以及土地利用/覆盖数据，分析了2000~2015年京津冀13个城市生长季及不同季节城市扩张对植被（ΔEVI）和地表城市热岛影响的时间变化趋势以及二者之间的关系，结果表明，京津冀13个城市主城区生长季及不同季节的城市扩张对植被均存在消极影响（ΔEVI<0），对夏季植被的影响最大（ΔEVI=-0.131）；白天和夜间的地表城市热岛强度（SUHII）最大值均出现在夏季，分别为2.594℃和1.859℃；不同季节的ΔEVI均值呈现显著下降趋势，其速率分别为-0.0038，-0.0033，-0.0045和-0.0018/a（P<0.01）；生长季、春季和夏季白天SUHII均呈显著增加趋势，速率分别为0.076，0.093和0.106℃/a（P<0.01），不同季节夜间SUHII均呈显著增加的趋势，其增加速率分别为0.05，0.055，0.049，0.054和0.046℃/a；京津冀13个城市主城区的ΔEVI均值和SUHII均值呈显著负相关（P<0.01），其相关系数介于-0.959~-0.592之间；白天SUHII与ΔEVI的相关性最高为生长季（r=-0.959），夜间SUHII与ΔEVI的相关性最高为春季（r=-0.936）.

Impacts of urbanization on vegetation growth and surface urban heat island intensity in the Beijing-Tianjin-Hebei

Based on the MODIS land surface temperature (LST) product, Enhanced Vegetation Index (EVI) product and land cover data, the impacts of urbanization on seasonal variations of vegetation growth (ΔEVI) and surface urban heat island intensity (SUHII) during 2000~2015 for thirteen major cities in the Beijing-Tianjin-Hebei region were analyzed. The results are as follows:urbanization has negative impacts on vegetation growth (ΔEVI<0) in all seasons for the thirteen major cities, and the lowest ΔEVI (-0.131) was found in summer. The highest daytime and nighttime SUHII were also found in summer, and the values was 2.594℃ and 1.859℃, respectively. The average ΔEVI decreased during 2000~2015 with an rate of -0.0038/a, -0.0033/a, -0.0045/a, and -0.0018/a (P<0.01) for the growing season, spring, summer, and autumn, respectively (P<0.01). The daytime SUHII from 2000 to 2015 exhibited significant linear increase with a rate of 0.076, 0.093, and 0.106℃/a for growing season, spring and summer, respectively (P<0.01). The nighttime SUHII from 2000 to 2015 also exhibited significant linear increase with a rate of 0.05, 0.055, 0.049, 0.054, and 0.046℃/a for growing season, spring, summer, autumn and winter, respectively (P<0.01). The ΔEVI had significant negative correlations with all-time SUHII for all the thirteen cities in the Beijing, Tianjin and Hebei region (P<0.01), ranging from -0.959to -0.592. The maximum correlation coefficient between the daytime SUHII and ΔEVI was found in the growing season (-0.959), and the maximum correlation coefficient between nighttime SUHII and ΔEVI was found in the spring (-0.936).