重庆南川区生态环境变化及其对城市不透水面的响应

Ecological environment changes and their responses to urban impervious surfaces in Nanchuan, Chongqing

城市建筑物的扩张使得不透水面挤占了大量的自然生态空间,利用遥感技术对生态环境进行监测有助于快速掌握区域生态变化过程。以重庆市生态典型示范区南川为研究区,利用2002、2011、2016年3期多时相Landsat影像,通过耦合绿度、湿度、干度、热度四个因子,计算各个时期的遥感生态指数(RSEI),并采用归一化不透水面指数提取各个年份的不透水面信息,借助景观格局指数揭示不透水面时空变化对区域生态的影响,最后结合人类活动范围以及经济、政策等多角度对区域生态环境变化进行分析。结果表明:(1)研究期内南川区的RSEI均值由0.6791下降至0.5712,再上升到0.6669,生态环境总体有所恢复。构成RSEI的四个因子中,对区域生态影响最大的是绿度指数,其次为干度指数。(2)2002—2016年间研究区不透水面扩张主要以内部填充为主,不透水面年增长率约为6.31%。(3)不透水面斑块面积较大、聚集度高、结合度强的区域RSEI值低,生态等级为优的区域相较生态质量差的区域聚集度低12%左右。(4)生态环境与人类活动范围、生态政策具有一定的相关性,与道路距离每增大100m,RSEI值提高约0.0149;积极的生态政策对区域生态环境具有促进作用。总的来说,合理利用现有不透水面进行建设,增加不透水面形态的复杂性和分散性,保护已有植被,注重经济增长与生态保护相协调是改善区域生态环境的关键。

As a result of the urban spatial expansion, a great deal of natural ecological space has been occupied by impervious surfaces. Under this circumstance, monitoring the ecological environment by remote sensing technology helps to master the regional ecological change process rapidly. Nanchuan, Chongqing, a typical ecological region, was chosen as the study area. Based on the Landsat images in 2002, 2011 and 2016;the greenness, humidity, dryness and heat were integrated to calculate the remote sensing ecological index(RSEI). Then normalized difference impervious surface index was used to extract the impervious surface information of the three years mentioned above. Furthermore, landscape pattern indices were used to display the impact on the regional ecology exerted by temporal–spatial variation of impervious surface. The regional ecological environment changes were analyzed from the perspectives of human activities, economy and policies. It turned out that the overall ecological environment index gradually recovered, with the mean RSEI values of Nanchuan dropped from 0.6791 to 0.5712, then increased to 0.6669 in the study years. Of the four indices that make up RSEI, greenness index had the greatest impact on the regional ecology, followed by the dryness index. Internal filling played a dominant role in the expansion of the impervious surface in the study area from 2002 to 2016, with an annual growth rate of 6.31% approximately.Moreover, areas with large average patch, high aggregation and strong cohesion had low RSEI values. Compared to superior ecological areas, inferior areas were about 12% lower in aggregation. The ecological environment had a certain correlation with the scope of human activities and ecological policies;the RSEI value raised by about 0.0149 for every 100 m increase in road distance, and positive ecological policies could promote the regional environment. In general, the key to improving the regional ecological environment is to rationally utilize the existing impervious surface for construction, increase the complexity and dispersion of impervious surface morphology, protect the existing vegetation, and pay attention to the coordination of economic growth and ecological protection.