Against the background of ecological civilization construction, optimizing the control of territorial spatial zoning has become an important
Against the background of ecological civilization construction, optimizing the control of territorial spatial zoning has become an important issue in maintaining regional ecological security. Clarifying different ecological processes and mechanisms within and among different ecological functional zones is of great practical significance for formulating refined spatial ecological management strategies. So far, research studies have focused on delineating ecological functional zones and analyzing linear processes and mechanisms within them, with little discussion on the differences in internal mechanisms and nonlinear characteristics of different ecological functional zones. Thus, it is necessary to elucidate key differences in the internal mechanisms and nonlinear threshold effects among different ecological functional zones to provide a scientific basis for establishing a territorial spatial zoning management system. In this study, the Integrated Valuation of Ecosystem Services and Trade-Offs model was used to evaluate ecosystem services in the Pearl River Delta region. Toward this, a self-organizing map was used to identify ecosystem service bundles, and geographically weighted regression and restrictive cubic spline analysis were used to clarify the key differences in trade-off/synergy networks and nonlinear thresholds among different ecosystem service bundles. Based on the results, suggestions for refined zoning and control of ecological spaces in the Pearl River Delta region are proposed. The results showed that: (1) In the Pearl River Delta, five different types of ecosystem service bundles are distributed in a circular pattern in space from the central to the surrounding areas: the urban-ecological, ecological-scarcity, agricultural-ecological, ecological-cooling, and ecological-conservation types. The ecological-conservation type accounted for 45.38% (the largest proportion), ecological-cooling for 32.80%, and ecological-scarcity for 10.73% of ecosystem service bundles; whereas neither the agricultural-ecological nor urban-ecological types accounted for more than 10%. (2) In the trade-off/synergy network of different ecosystem service bundles, the synergistic relationship between carbon storage and urban cooling remained stable, whereas the relationships between other ecosystem services showed significant differences. Among the five bundles, the trade-off/synergy interaction of the urban-ecological type was the strongest, followed by that of the agricultural-ecological and ecological-conservation types, whereas that of the ecological-cooling and ecological-scarcity types were relatively weak. (3) There were significant differences in the nonlinear threshold effects between the Multiple Ecosystem Services Landscape Index (MESLI) and six identified driving factors in the different ecosystem service bundles. In the ecological conservation and ecological scarcity types, the MESLI exhibited nonlinear relationships with all six factors and clear critical thresholds. The MESLIs of the agricultural ecological and ecological cooling types exhibited nonlinear relationships with elevation, night light, gross domestic product density, and population density, whereas that of the urban ecological type only exhibited nonlinear relationships with elevation and population density. (4) We suggest that decision makers use nonlinear thresholds as references to demarcate key control areas for each ecosystem service bundle, clarify their dominant mechanisms based on trade-off/synergy networks, and develop different control indicators in a targeted manner. In conclusion. this study identified key differences in trade-off/synergy networks and nonlinear threshold effects among different ecosystem service bundles and explored different ecological zoning and control strategies for the Pearl River Delta region, providing a theoretical basis and indicator references for refined management of territorial spaces in urban agglomeration areas.
