Objective  The 2020 Guidelines for the Preparation of Municipal Territorial Spatial Planning sets new requirements for the efficient allocation of ecological spatial elements and the composite enhancement of ecological functions. At present, how to solve such problems as the imbalance of ecosystem services, lack of integration of ecological elements and improper linkage with territorial spatial planning has become a hotspot of general concern in ecological spatial planning theory research in the academic circle of planning, while there is still a lack of research on the key technical pathways with respect to the core content of ecological spatial planning in China. Based on the requirements of spatial planning system in the new era, this research identifies the supporting role of green infrastructure (GI) planning in spatial planning reform from the perspective that ecosystem services can synergistically enhance the internal response, the natural resource value response and the integration of ecological spatial planning.

Methods  According to the relationship between GI planning and ecosystem services in the new era, and based on the spatial planning system of China and the synergy of multiple ecological functions, this research analyzes the spatial characteristics of land surface in combination with the principle of landscape ecology, the theory of urban and rural planning and the decision-making method of system synergy, and identifies the synergy and trade-offs between the target ecosystem services.

Results  The logical core of GI planning is to achieve system synergy among multiple ecosystem service objectives, to coordinate the interaction between target ecosystem services and to achieve a balance between the supply and demand of ecosystem services. In conjunction with landscape ecology, this research constructs a theoretical framework of synergistic "process – pattern – scale – function" planning at the city-site scale, which completes the GI planning theory of functional synergy and supply-demand balance. Meanwhile, the research constructs a multi-dimensional GI technical framework of "system – process – relationship", which is described in detail as follows from each dimension involved. From the system dimension, the GI planning system framework of "(2+3+4) × X" is established based on the theoretical framework of GI planning, which presents the characteristics of "single-objective classification and grading" and "multi-objective coupling and optimization", and is linked to the municipal level in the current five-level and three-class system of territorial spatial planning from multiple perspectives of strategy, integrity, professionalism and implementation. Specifically, "2" means two levels of GI network building, "3" means three steps to build ecological network at the urban scale, and "4" means four levels of enhancement of ecological functions at the site scale. The "X" means integrating the objectives of ecosystem services based on the clarification of the internal relations and ecological processes of network elements, so that all single-objective GI networks can be combined into an integrated GI network by vertical superposition, with the inner links and primary and secondary relations there between being identified. Concerning the classification and grading standard of the spatial planning system, the research shows that the geographical area planning is part of the special planning system that focuses on the construction of spatial patterns and the enhancement of ecological functions. In terms of planning timing, the research proposes to clarify the implementation plans for priority planning actions, and formulate a list of key conservation and restoration projects, accompanied by relevant supporting policies; in terms of planning transmission, the research proposes that rigid indicators and targeted control measures should be used to constrain and guide relevant plans at the lower level. From the process dimension, the six technical aspects of "investigation and identification – target decomposition – assessment and zoning – pattern construction – function control – target coupling" are highlighted with the objective of systemic synergistic enhancement of ecosystem service functions, and the key preparation process of GI planning is clarified. From the relationship dimension, the research constructs an ecological spatial planning system from such aspects as structural shaping, systematic layout and special regulation, and controls and guides the macro pattern and the functions of GI elements at the site level through "indicators + lists". In the meantime, in order to integrate the control zones in the master plan of municipal territorial spatial planning, the concept of "red line", "green line" and "blue line" of the territorial spatial planning system is combined with rigid and elastic GI grading control measures.

Conclusion  GI planning is a systematic and complex ecological management tool that adapts to the concept of ecological civilization and the construction of the territorial spatial planning system in the new era. GI planning with coordinated multi-ecosystem service objectives can effectively respond to the typical ecological and environmental problems of a complex system of cities, and can balance the supply of multiple ecosystem services, balance the supply and demand of ecosystem services, suppress and reduce negative impacts, and promote the overall optimization of ecosystem benefits. The research results will serve as an inspiration for the establishment of a theoretical system of territorial spatial planning, provide theoretical support for the networked and systematic reconstruction and functional optimization of the ecological spatial pattern under municipal territorial spatial planning, and provide a technical basis for the preparation of special ecological spatial planning in terms of technical framework, workflow and control means, and thus have the dual value of theoretical reference research and practical reference for GI planning and design.