The influence of climate and human factors on a regional heat island in the Zhengzhou metropolitan area, China.

The development of urbanization and the establishment of metropolitan areas causes the urban heat island to cross the original single-city scale and form a regional heat island (RHI) with a larger influence range. Due to the decreasing distance between cities, there is an urgent need to reevaluate RHI for urban agglomerations, considering all cities instead of a conventional single-city perspective. The impact of climatic conditions and human factors on heat islands still lacks a general method and framework for systematic evaluation. Therefore, we used land and night light data as background conditions to study the diurnal and seasonal changes of heat islands in the Zhengzhou metropolitan area, China. Pearson correlation analysis and random forest regression analysis were then used to explore the influence of climatic conditions and human factors on RHI and its internal relationship. We found that the daytime RHI had strong spatial heterogeneity and seasonal differences from 2001 to 2020. The daytime RHI was stronger than nighttime in spring, summer, and autumn, and the nighttime RHI was stronger than daytime in winter. From spring to winter, RHI increased first and then decreased during the daytime, while the opposite was observed at night. In this study, temperature has a greater effect on daytime RHI; CO2 and NL have a greater effect on nighttime RHI. There was strong spatial heterogeneity in the effects of climatic conditions and human factors on the RHI, with climatic conditions contributing more to the daytime RHI in the northern mountainous areas, while human factors had a greater impact on the nighttime RHI in the main urban areas of each location. The results of this study highlight more targeted and informed strategies for RHI mitigation in the Zhengzhou metropolitan area and provide helpful insights into RHI evaluation in other urban agglomerations.

Temporal variation and spatial scale dependency of the trade-offs and synergies among multiple ecosystem services in the Taihu Lake Basin of China.

Grasping the temporal-spatial characteristics of interactions and spatial scales of multiple ecosystem services is the foundation for sustainable ecosystem management. Eight ecosystem services, including crop production, freshwater supply, aquatic production, net primary production, soil conservation, water retention, flood regulation, and forest recreation were measured at the 1-km2 pixel scale in the Taihu Lake Basin (TLB) of China from 1990 to 2010. Furthermore, we quantified the trade-offs and synergies of services at different periods of urbanization and across the 1-km2 pixel scale and the county scale. We aim to find which ecosystem services interactions temporally vary and depend on spatial scale. Our results found that: 1). Tremendous amount of cultivated lands were converted to construction land, and rapidly shrank from 1990 to 2010. 2). Determined by land use, different ecosystem services had spatial heterogeneity of their strength. Ecosystem services hot spots experienced an increasing trend while cold spots showed a trend of decreasing first and then increasing from 1990 to 2010. 3). Trade-offs between provisioning services and regulating services at the 1-km2 pixel scale changed over time. There was a new synergy between freshwater supply and aquatic production at the 1-km2 pixel scale in 2010 with the human demand. 4). From 1990 to 2010, the changes of provisioning services led to trade-offs among provisioning services, regulating services and cultural services at two scales. Taking temporal variation and scale dependence into account, this research is helpful to the delineation of "Ecological Conservation Redline" and implement the project of "Grain for Green". We also provide suggestions for maintaining ecosystem services with economic growth in China's Yangtze River Economic Belt for land use policies and decision making.