Research on the Complexity of Forms and Structures of Urban Green Spaces Based on Fractal Models

The fractal nature of urban green spaces is the product of the self-organizing evolution of the complex urban system into a higher stage, and orderly patterns and complex structures of urban green spaces will tend to manifest after they develop to a certain stage. On the basis of GF1 satellite data in 2019 and three fractal models, the complexity of the forms and structures of a green space system in downtown Dalian, China, was studied. The results showed that the boundary dimension measured by the perimeter-scale model was 0.64–1.40, and the boundary dimension measured by the area-perimeter model was 1.79–1.99; these results indicate that the degree of human disturbance in green space boundaries was high, and the stability of the green space spatial structures was poor. The grid dimension measured by the area-scale model was 0.49–1.42, and the average radius dimension measured by the area-radius model was 0.35–0.76; these results indicate that the balance of the spatial distribution of green spaces was low, and the green spaces were excessively concentrated in the city center. Through comparisons of the scaling range among various types of green spaces, the characteristic range (gradient structure) of the spatial distribution of urban green spaces was found, which can reflect the maturity of green space growth and the quality of the green space layout. The gradient structure of green spaces in Dalian was characterized by three gradients, namely, 0–4000 m, 4000–8000 m, and 8000–16,000 m. The development of green spaces in the first gradient zone was the best, and the second and third gradient zones showed relatively large potential for improvement. These research results are of practical significance for guiding the planning and construction of green spaces in urban areas.