京津冀地区不透水表面覆盖率的时空演变及其对植被的影响

Spatiotemporal evolution of impervious surface percentage and its impact on vegetation in Beijing-Tianjin-Hebei region

基于不透水表面和MODIS增强型植被指数(EVI)数据,辅以分段线性回归、趋势分析等方法,定量分析2000—2018年京津冀不透水表面覆盖率(ISP)的时空演变及其对植被的影响。结果表明:①京津冀ISP呈显著增加的趋势,增速为0.024%/a(P<0.01)。分阶段来看,2000—2010年和2011—2018年ISP均呈显著增加趋势,增速分别为0.019%/a(P<0.01)和0.037%/a(P<0.01),后一阶段的增速快于前一阶段;②空间上,ISP快速增加的区域主要位于城市和近郊,缓慢增加和增加的区域主要位于主城区和农村;③从不同ISP区域ΔEVI的时间变化趋势来看,城区、近郊和远郊的ΔEVI均呈显著下降趋势(P<0.05)的地市分别有6个、6个和3个。主城区的ΔEVI呈显著增加趋势的地市有3个(P<0.05)。从EVI的空间变化趋势来看,显著增加的区域主要位于北京、天津等市的主城区,显著减少的区域主要位于北京、天津、石家庄等地市的近郊和远郊;④从EVI随ISP的空间变化趋势看,所有地市EVI随ISP的增加均呈显著减小的趋势(P<0.01)。减小趋势最大和最小的地市分别为秦皇岛和张家口,其下降速率为-0.0081/a和-0.0043/a。从时间变化来看,京津冀的EVI与ISP呈显著负相关,其相关系数为-0.4912。研究结果可为中国城市快速扩张过程中的植被变化提供理论参考和科学实践。

Exploring the urbanization effects on vegetation is crucial for the urban ecological management and green space planning.Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index(MODIS-EVI)and impervious surface data from 2000 to 2018 were utilized to assess the spatiotemporal impervious surface percentage(ISP)and its impact on vegetation by the piecewise regression model,trend analysis,and correlation analysis.Results indicated that(1)During the whole period,the ISP significantly increased(P<0.01),with the linear tendency being 0.024%/a.There existed two distinct periods with different increasing trends,with the linear tendency being 0.0019/a(P<0.01)and 0.0037/a(P<0.01)in terms of 2000-2010 and 2011-2018,respectively.The ISP from 2011 to 2018 increased faster than that from 2000 to 2010.(2)Rapid increases in the ISP were mainly distributed in the urban(0.5<ISP≤0.75)and suburban(0.25<ISP≤0.5)areas.Slow increases in the ISP were mainly distributed in the urban core(0.75<ISP≤1)and rural areas(0<ISP≤0.05).(3)From the perspective of change trends of rural EVI and theΔEVI in urban areas,the areas with significant decreased ISP were mainly distributed in the urban,suburban,and exurban areas.TheΔEVI decreased significantly in urban,suburban and exurban areas for 6 of 13 cities,6 of13 cities and 3 of 13 cities,respectively(P<0.05).By contrast,the areas with increased ISP were mainly distributed in the urban core,and increased significantly for cities of Beijing,Tianjin and Baoding(P<0.05).The stable or even significant increase trend ofΔEVI in the urban core(0.75<ISP≤1)in most cities in Beijing-Tianjin-Hebei region could primarily be attributed to the positive effects derived from the urban ecological environment,and improvement of the preservation and construction of the urban green space.In terms of spatial variation,EVI increased significantly in the urban cores of Beijing and Tianjin,and decreased significantly in the suburban and exurban areas of Beijing,Tianjin and Shijiazhuang.(4)As for spatial trends,the annual maximum EVI from 2000 to 2018 decreased significantly(P<0.05)with elevating ISP for all the cities in the Beijing-Tianjin-Hebei region.The highest decaying rate was observed in Qinhuangdao(-0.0081/a),while the lowest decaying rate was found in Zhangjiakou(-0.0043/a).From the view of temporal variation,significant negative correlation between ISP and EVI was found in the study region and the correlation coefficient was-0.4912.The results can provide scientific and theoretical basis for research on vegetation change in the process of rapid urban expansion in China.