[Differentiation Impact of Urban Form on Heat Island Intensity Along Urban Development Gradients in Zhengzhou].

The impact mechanism of urban form on heat island intensity （HI） is a core issue of research attention. Existing achievements have mostly focused on the correlation between urban form and thermal environment. Research on the differences along urban development gradients, and research on marginal effects and optimization paths under gradient differences is relatively scarce. This study considered the central urban area of Zhengzhou as an example, based on multi-source data such as Landsat remote sensing images and NPP-VIIRS satellite night light remote sensing images, and introduced a gradient-enhanced regression tree model to improve the DEMATEL-ISM method, exploring the gradient differences and marginal effects of urban morphology on heat island intensity. The results showed that： ① From 2006 to 2020, the HI decreased with the increase in urban development gradient, and the increasing trend slowed down annually. ② The gradient difference between urban form and HI was significant. The green space form index always had a strong impact on HI, among which, NDVI was the most significant variable within each gradient, and the impact intensity of the construction land pattern index increased significantly with the increase in gradient, whereas the role of building combination form index weakened accordingly. ③ According to the ISM model, a four story-three order structural model of urban form indicators was obtained. The construction land pattern indicator within the high intensity construction gradient was the root cause order, and the building combination form indicator within the low intensity construction gradient was the root cause order. ④ The differences in the marginal effect of urban form along the gradient were significant. As the value of the indicator increased, its impact intensity and direction would change. There were differences in the key indicators and threshold ranges that affected the intensity of HI within different gradients. The study proposes a marginal optimization method for urban form based on the improvement of the urban thermal environment under the differences along urban development gradients, providing refined practical reference for orderly urban expansion and coordinated urban-rural development.