Law and mechanism of spatio-temporal evolution of urban greenspace in the lower reaches of the Yellow River

  Objective  Greenspace is the ecological foundation of urban and rural development, and a good greenspace system is an important guarantee for coordinating urban development and nature conservation. Comprehensive measurement and investigation of the spatio-temporal evolution pattern of city-wide greenspace in the lower reaches of the Yellow River can help the planning for the construction of ecological corridors in the lower reaches and ecological improvement in the floodplain.

  Method  Four cities in the lower reaches of the Yellow River, Jinan, Heze, Zhengzhou, and Xinxiang, were used as the study objects, and year 1990, 2000, 2010, and 2020 were taken as the time nodes. Using vegetation cover density and the secondary classification of land use, the city-wide green space types were classified, and then the transfer matrix, landscape pattern indices, urban-to-rural trajectory and geo-detector were used to conduct quantitative research on the spatio-temporal patterns and mechanism of city-wide evolution greenspace.

  Result  (1) In the past 30 years, the greenspace had transferred 3 223 km² to the bare surface, and the bare surface had transferred 181 km² to all kinds of greenspace; 735 km² of greenspace was transferred to each other, of which 466 km² was transferred from higher density to lower density greenspace, and 269 km² was transferred from lower density to higher density greenspace. (2) The decrease of percentage of landscape (PLAND) and area-weighted mean shape index (AWMSI) of sparse greenspace, the decrease of number of patches (NP) of all kinds of greenspace, and the increase of mean patch size (MPS) and functional connectivity (PC) were the general rules of landscape pattern indices. (3) On the urban-rural gradient, the peaks and valleys of low density greenspaces moved significantly, while high and medium density greenspaces were relatively fixed. (4) The influence of natural environmental factors on the geographical distribution of greenspace in Jinan, Shandong Province of eastern China, Zhengzhou and Xinxiang, Henan Province of central China was dominant, and the cumulative influence of socio-economic factors in each city increased by 3.1%−8.4%, showing an increasingly obvious non-linear enhancement with natural environmental factors. influence of socio-economic factors in each city increased by 3.1%−8.4%, showing an increasingly obvious non-linear enhancement with natural environmental factors.

  Conclusion  During the 30 years, the total amount of regional greenspace is lost, and the internal transfer of greenspace is mainly from higher density to lower density, with more transfers along the edges of built-up areas and along the wide floodplain; the overall trend of landscape pattern changes from obvious fluctuation to nearly stable, from fragmentation and dispersion to integration and connectivity, and the improvement trend is more obvious in regional central cities; the urban-to-rural trajectory characteristics differ greatly between cities and greenspace types; the synergistic effect among influencing factors is gradually increasing, and greenspace gradually becomes the result of natural-social interconfiguration. In the future, the city-wide greenspace should be transformed from a “barrier” to a “hub” according to the needs of the city.