Urban niche in the Guangdong-Hong Kong-Macao Greater Bay Area from the perspective of multiple space of flows

Based on the multi- directional flow matrix and the social network analysis, the paper proposes a system extending and optimizing the connotation and measurement of urban niche, constructs a research framework of urban niche in urban agglomerations from the perspective of space of flows, and takes the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as a case to dissect the "ecostate- ecorole" characteristics of cities, revealing niche and competition and cooperation relationships of cities. The study shows that: (1) In terms of the overall ecorole, the rank-size distribution of inter-city factor flows in the GBA is the primacy ratio distribution at the level of employment service flow, economic service flow, knowledge flow and ecological service flow, while it is the centralized one at the level of information flow, and the balanced one at the level of comprehensive flow and cooperation flow, with a log- normal distribution pattern. (2) In terms of local ecorole, the city group varies depending on factor flows and is interweaved with each other to form a multi- dimensional flow intensity structure of "core- regional core- margin", of which, Hong Kong and Shenzhen, Guangzhou and Foshan, Zhuhai and Macao, share the closest inter-city cooperation. Meanwhile, three inland city groups show signs, namely, "Guangzhou- Foshan-Zhaoqing", "Shenzhen-Dongguan-Huizhou" and "Zhuhai-Zhongshan-Jiangmen". (3) In terms of macro ecostate, cities play different roles in different factor flows of urban agglomerations, which can be summarized into five types: diffused, benefited, balanced, isolated and intermediary. Also, the participation modes of cities in clusters can be grouped as participation in full and in part, according to the analysis of intercity dominant flow in each factor matrix. (4) In terms of micro ecostate, cities share complex partnership and competitive relationship. There are 11 pairs of reciprocal partners, 7 pairs of complementary partners, 42 pairs of fierce competitors and 31 pairs of mild competitors. Based on the flow data, the paper broadens the perspective of study on urban niche of urban agglomerations, and puts forward a new idea of improving the spatial structure of urban agglomerations and regional competition and cooperation relationships, so as to provide a valuable decision-making basis for building the GBA into the world-class city cluster. © 2023 Science Press. All rights reserved.