Typical place communities in two patterns
Based on our perception of daily life phenomena, there are two spatial patterns of "specialization and cooperation" and "mixed" (Fig. 1). This so-called "specialization and cooperation" pattern refers to the place communities in which the same types of places form a place cluster (specialization), and different place clusters locate adjacent to each other (cooperation). For example, similar manufacturing enterprises are distributed in the same industrial park forming a manufacture cluster at a small scale, and a snack cluster composed of many snack shops locates adjacent to this manufacture cluster at a larger scale. The so-called "mixed" pattern refers to those place communities in which places are highly mixed together at all scales. For instance, cold drink shops and restaurants usually cluster closely together at any scale.
It is of great significance for extracting urban spatial units in urban planning and design practice to distinguish these two patterns. Thus we creatively propose a grid adjacent network analysis method on the basis of grid co-location probability concept in the evolutionary economic geography 33–38. The concept of grid adjacent probability can be commonly understood as the probability of two place types locating on two adjacent grids. Therefore, the simultaneous analysis of grid co-location probability and grid adjacent probability can distinguish the “specialization and cooperation” and “mixed” patterns among intra-urban place communities. As the grid scale becomes rougher, a pair of place types enters the “agglomeration mode” at a certain scale when both the co-location and adjacent probability of these two place types are significantly high (above the top quartile), and exits from the “agglomeration mode” when either of the co-location and adjacent probability is below the top quartile. Prior to the agglomeration mode, if the pair's co-location probability is significantly high while its adjacent probability is not, the agglomeration pattern of this point pair is defined as the “specialization & cooperation” pattern; otherwise, it is defined as the “mixed” pattern. In this paper, the pairs that have entered the agglomeration mode twice or more are excluded since they are in an unstable agglomeration state.
As the minimum grid in this study is at 200-meter scale, it is impossible to distinguish the mixed pattern from the specialization & cooperation pattern when a place pair enters the agglomeration mode at 200 m. Therefore, we will discuss this situation separately which calls for following-up studies at finer scales than 200 meters.
Three agglomeration cubes are constructed to vividly demonstrate the entering and exiting scales for each place pair (Fig. 2). With the aid of these three agglomeration cubes, the significant agglomeration place pairs can be discovered and their agglomeration entering scales can be determined. To further exact typical place communities, the co-location (Cube B and C) or adjacent (Cube A) probability for each place pair at the agglomeration entering scale is normalized and recorded as the edge weight, and we take each place type as a node to construct a significant agglomeration place network for each of the three cubes. Then the total 23 typical place communities are further extracted using the modularity algorithm in Gephi 9.2 software (Fig. 3).
Agglomeration logic and scale of place communities
For the 23 typical place communities extracted from the three agglomeration cubes above, what factors lead to the spatial concentration among different place types? It is far from enough to answer this question only from the economic perspective of Jacobs externality. Because the city is an open dissipative system with both self-organization evolution process and hetero-organization process, within which the law of market economy is merely a rule in the self-organization process. In addition, the distribution of intra-urban places is also affected by environmental, political, cultural and other factors. To sort out the complex factors on the intra-urban place communities, here we construct a theory of place niche for socio-economic systems in light of the well-grounded ecological niche theory in natural systems.
The ecological niche theory describes the phenomenon that different species occupy specific habitats and activity areas on the earth through fierce competition for environmental resources and the interaction of complex predation and symbiosis between species 39–41. Judging from the definition, it is clear to see that there are three core concepts of ecological niche: the first one is the spatial habitat area of species (also generally known as spatial ecological niche), the second one refers to the resource constraint set (a high-dimensional space composed of adaptive fitness functions to various environmental resources), and the third one is the food chain (predation marks as the most essential interrelationship between species, and there exists Lindeman's 10% law during the process of energy flow through the food chain, forming the biomass pyramid 42).
Since the inner relation within an ecological community can be well explained by the theory of ecological niche, a new theory of place niche is demanded urgently to explain the complex concentration logic inside a place community. In fact, socio-economic place systems share many similarities with ecosystems, for instance, both have different preferences for environmental resources and complex interactions among species. Here we define the place niche as the phenomenon of various man-made facility places occupying specific areas on the earth’s surface for different environmental resource preferences (including resources in the natural environment and in the artificial environment), through the interaction of competition and complementation (Fig. 4).
With the help of place niche concept, we proceed to elaborate the agglomeration dynamism within various typical place communities. Here we introduce the concept of overall attraction of a location on the earth’s surface for an ecological/place species, which is the sum of the environmental factors and inter-relationships between species that affect the spatial distribution of species. The spatial implication for both ecological and place communities is that a location enjoys high overall attraction for multiple species, which leads to the gathering of multiple species at this location. The overall attraction of a location can be categorized into two components: the environmental component and the inter-specific component. In ecosystems, the environmental component is mainly comprised of abiotic environmental resources such as temperature, soil, and air, and the inter-specific component is mainly linked through the food chain, since predation is the most important relationship among species. Whereas it is more complex for socio-economic place systems with two divergences. First, in addition to purely surface natural attributes, the environmental component also contains the influence of the artificial built environment, which is often referred to as the first nature and the second nature in the discipline of economic geography 43. The accessibility determined by the structure of the road network directly affects land rent. Just as the fertility of the soil largely determines the total biomass of the ecological community, so the land rent in the socio-economic place system largely determines the intensity of building development. Secondly, the inter-species relationship of socio-economic place system is much more complicated than that in the ecosystem, which can be regarded as a self-organized process governed by the law of evolution 44. As a mixed self-organized and hetero-organized system, human society boasts the self-organized evolutionary relationship governed by the law of market economy and other centralized hetero-organized behaviors, such as urban planning like various administrative interventions. In summary, there are four components for the overall attraction of location to a place type in socio-economic place system: the natural environment component, the artificial environment component, the self-organized behavior component and the hetero-organized behavior component. To put it simply, they are environmental, transportation, political and economic factors, which explain the logic of agglomeration dynamism within various typical place communities.
To examine the intrinsic logic of the intra-urban place communities in a finer way, a process model is built to show the specific interactions among the intra-urban places. Based on the input-output table of national economy of China in 2017, we create the “place white box” model (Fig. 5) -- an intra-urban socio-economic process model consisted of various socio-economic subjects corresponding to different place types. Based on our daily experience, we classify socio-economic subjects into three categories of governments, enterprises and residents, among which the enterprises are categorized into manufacturing, consumer services and producer services, adding public goods provided by the government and various external transportation hubs in an attempt to comprehensively demonstrate the complex interaction dynamism within urban socio-economic systems. The interaction between various socio-economic subjects is realized through various material and information flow.
For the above 23 typical types of intra-urban place communities, their main inner-interaction routes are simulated and categorized to the four impact factors (i.e. political, economic, transportation and environmental) in the place white box model. In particular, the economic linkages are complex: (1) at the production end, it is mainly linked through the direct supply and demand of products and services between different place types within a place community. (2) at the consumption end, the interaction among consumer places is maintained through the complementary relationship between products and services (such as the relationship between cinemas and restaurants in shopping malls, the attraction of shopping malls to consumers is enhanced as both can meet the needs of consumers for various weekend leisure activities), and the gathering of the same type of places to provide consumers with diversified choice dividends. (3) there is another situation where consumption places gather around production places. Take an example, snack places gather around industrial parks and government agencies, with the aim to provide work meals for the employed people in these workplaces.
The specific analysis is carried out here to elaborate the internal agglomeration logic of 23 typical place communities in three cubes through the place white box model.
Cube A: the specialization & cooperation pattern with agglomeration entering scale rougher than 200 meters
Typical place communities for this pattern mainly focus on transportation hubs (airports, highway service areas, toll stations, public parking lots, terminals) with the following three situations.
1) The first one refers to the outward-oriented high-tech manufacturing and advanced producer service (APS), whose industrial cycle exceeds that scope of the local city. So they are distributed around the external transportation hub to enhance the efficiency of the industrial cycle.
2) The second one is the consumer service facilities around the highway service areas, which include fast hotels, apartments, and local specialty restaurants, provide catering and accommodation services for logistics industry staff.
3) The third one is the urban leisure and public culture place communities forming around the urban inner transportation hubs such as piers, subways and public parking lots, which mainly rely on sound urban transportation accessibility and superior natural environment (usually leisure piers), and generate intra-community interactions through shared consumers.
Cube B: the mixed pattern with agglomeration entering scale rougher than 200 meters
The intra-community linkages are roughly divided into production-end linkages and consumption-end linkages.
1) Production-end linkages are mainly weak linkages between manufacturing industries (not the most significant direct upstream and downstream relationships, such as the relationship between electronic components and chemical fiber industries) and linkages between production services and manufacturing industries.
2) Consumption-end linkages are created by sharing specific types of consumers, such as communities of parent-child places around taekwondo gyms, communities of residential services around bath and massage, and communities of leisure and resort places surrounding four-star hotels.
3)It should be noted that there is another type of place communities, in which places concentrate passively due to the environmental conservation requirements, such as paper manufacturing and non-ferrous metal manufacturing in heavy industry category.
Cube C: the unidentified patterns with agglomeration entering scale at 200 meters
The distinctive feature of this type of place communities is the similarity of the place types within the communities, i.e. basically the communities are made up of a large number of similar place types with three main types of interaction: productive, consumptive and employment-consumptive.
1) Productive linkages mainly refer to the strong links among manufacturing enterprises (direct upstream and downstream relationships, e.g., chemical fibers and textiles) and close links among producer services (strong linkages among investment, cultural & creative and technical services) and some linkages between producer services and manufacturing (linkages between technical services and electronic components)
2) Consumptive linkages are mainly several consumptive places that share similar consumers, such as subdivisions within broad categories of hotels, health care, sports, culture, restaurants and entertainment.
3) Employment-consumptive linkages exist in the communities composed of snacks distributed around the government places, where the catering places serves government employees in close proximity.
Eventually, 11 inner interaction linkage types under four main impact factors are summarized for the 23 typical place communities (Table 1).
Table 1
The interaction routes and main impact factors for the 23 typical intra-urban place communities for three Cubes.
Community ID
|
Core Place Type
|
Linkage Path in Fig. 5
|
Agglomeration Pattern
|
Agglomeration Scale
|
Main Impact Factor
|
A01
|
Toll Station
|
10 + 21, 16 + 22
|
Specialization & Cooperation
|
3,000–4,000 m
|
Transportation Economy (Productive)
|
A02
|
Wharf, Subway
|
13
|
Specialization & Cooperation
|
400–1,000 m
|
Environment, Economy (Consumptive)
|
A03
|
Archives and Memorial Hall
|
13
|
Specialization & Cooperation
|
400 m
|
Environment, Economy (Consumptive)
|
A04
|
Snack, General Industrial Park
|
16 + 22
|
Specialization & Cooperation
|
3,000–5,000 m
|
Economy (Consumptive)
|
A05
|
Airport
|
10 + 21, 19 + 21
|
Specialization & Cooperation
|
1,000–3,000 m
|
Transportation, Economy (Productive)
|
A06
|
Expressway Service Zone
|
18 + 21, 17 + 21
|
Specialization & Cooperation
|
3,000–4,000 m
|
Transportation, Politics and Economy (Consumptive)
|
A07
|
Public Parking
|
03, 16 + 23
|
Specialization & Cooperation
|
1,000–2,000 m
|
Economy (Consumptive)
|
B01
|
Long-distance Bus Station, City Square
|
03, 17 + 21
|
mixed
|
400–600 m
|
Economy (Consumptive), Transportation
|
B02
|
Taekwondo, Theme Hotel
|
03
|
mixed
|
400 m
|
Economy (Consumptive)
|
B03
|
Ferrous Metal, Snack
|
01, 19 + 22
|
mixed
|
3,000 m
|
Environment, Economy (Consumptive)
|
B04
|
Bath and Massage, Real Estate Agent
|
03
|
mixed
|
2,000 m
|
Economy (Consumptive)
|
B05
|
Electronic Equipment Manufacturing
|
01
|
mixed
|
2,000 m
|
Economy (Productive)
|
B06
|
Four-star Hotel, Billiards Rooms
|
03
|
mixed
|
400–600 m
|
Economy (Consumptive)
|
B07
|
Training Institutions, Gymnasium
|
03
|
mixed
|
2,000 m
|
Economy (Consumptive)
|
B08
|
Appraisal Firm
|
11, 17 + 23
|
mixed
|
600 m
|
Economy (Employment-consumptive)
|
C01
|
Museum, National and Provincial Institutions
|
03, 13
|
unidentified
|
< 200 m
|
Economy (Consumptive)
|
C02
|
Gymnasium
|
03, 13
|
unidentified
|
< 200 m
|
Economy (Consumptive)
|
C03
|
Cinema, Japanese Restaurant
|
03
|
unidentified
|
< 200 m
|
Economy (Consumptive)
|
C04
|
Train Station, First-aid Center
|
03, 17 + 21
|
unidentified
|
< 200 m
|
Transportation, Economy (Consumptive)
|
C05
|
Mala Tang, County Institution
|
03, 16 + 22
|
unidentified
|
< 200 m
|
Economy (Consumptive)
|
C06
|
Boutique Hotel, Apartment
|
03
|
unidentified
|
< 200 m
|
Economy (Consumptive)
|
C07
|
Chemical Products Manufacturing
|
01
|
unidentified
|
< 200 m
|
Economy (Productive)
|
C08
|
Fuel Processing, Investment Company
|
01
11
|
unidentified
|
< 200 m
|
Economy (Productive)
|
1) Place communities dominated by economic factors with agglomeration scale finer than 200 m
Productive linkages
①strong linkages in mixed pattern -- direct upstream and downstream linkage of industry chain with agglomeration scale finer than 200 meters; ②weak linkages in specialization & cooperation pattern -- indirect linkages in industry chain with agglomeration scale of 2,000 meters.
Consumptive linkages
by sharing similar consumers, places within the same categories concentrate at the scale finer than 200 meters, while places belonging to different categories measure at the scale of 400 meters or 2,000 meters.
Employment-consumptive linkages
consumer services gather around major employment places such as governments at the scale finer than 200 meters.
2) Place communities dominated by transportation factors with agglomeration scale over 2,000 m
Outward-oriented industries around external transportation hubs
outward-oriented high-tech manufacturing (electronic components, etc.) and advanced producer services (investment companies, technical services, etc.) gather around the airport, forming communities with a scope of 2,000–5,000 meters in the specialization & cooperation pattern.
Consumer services surrounding the external transportation hubs
consumer service places such as fast hotels and local cuisine gather around highway service areas, forming communities with a scope of 3,000–5,000 meters.
Cultural and commercial facilities around inner-city transportation hubs
e.g. cultural palaces and theaters gather around public parking lots, forming communities with a scope of 2,000 meters.
3) Place communities dominated by environmental factors with agglomeration scale within 400–1,000 m
Communities around beautiful environment and open space
e.g., leisure and entertainment facilities built around waterfront piers with the gathering scope of 400–1000 meters.
Communities boasting historical and cultural resources
influenced by the urbanization and generation process, these places are equipped with basic urban functions, like hospitals and schools usually locate at historic center areas, forming a type of place communities around memorial halls converted by historical residences or historical buildings at the scope of 400 meters.
Communities with environmental pollution restrictions
due to the environmental pollution restrictions, chemical, paper and other heavy pollution enterprises are often restricted by urban planning regulations to adjacent suburban locations, forming place communities of heavy pollution industries with the spatial scope of 3,000 meters.
4) Place communities dominated by political factors with agglomeration scale over 2,000 m
Political communities providing public goods to relocate urban functions
government, scientific research institutions and other government-supplied places, which are not oriented by market laws, usually distribute according to the government’s willing to relocate urban core functions. Therefore, these government’s places usually keep in close proximity to expressway service areas in the suburban, forming a suburban place community of 4,000-meter spatial scope.
Communities in industrial parks
there are no direct linkages among some manufacturing industries (e.g., agricultural processing and furniture manufacturing), but they concentrate together because of industrial park development strategy at the scale of 2,000 meters.
Attentions should be paid to the fact that the place niche theory does not well explain the ratio of different place types within place communities. However, based on Lindeman's 10% law of energy-flowing pyramid in food chains, a negentropy-flowing pyramid in industrial chains can be built to reveal the quantitative relationship between place types (Graph 19 in Fig. 4). Since various living organisms including human society are open dissipative systems in essence, they are all evolving to construct more ordered and complex structure and obtain more free energy by constantly taking in negentropy of matter, energy and information. However, the specific negentropy's metric in the chain requires further in-depth analysis.
As for the constraints on the quantitative relationships within a particular localized place community, a conservation analysis needs to be performed according to the specific interactions of the place community by a specific type of flow. For instance, the consumptive place communities need to be analyzed with time-consuming constraints, as the consumers’ time is “eaten” by various consumptive places. Productive communities, on the other hand, should be analyzed through material flows. It’s in line with the circular economy and carbon neutral concept promoted today.
Systematic spatial layout model of place communities
How are the typical intra-urban place communities identified above embedded into urban space and form the overall spatial structure in the city? This question will be discussed in the following.
With regard to the structure of intra-urban place communities, a clear intra-urban hierarchy, which is gradually outlined by a series of studies traced to the central place theory and focuses on the commercial, office and service centers, is formed by the combination of two scales: (1) one is the physiological scale, which is determined by the spatial and temporal constraints of individual travel scope, includes the classical Marchetti constant 45 (a person spends one hour per day on commuting at different cities of any country), travel-time-ratio (TTR) [48], and other theories, which explain the concentric structure of everyday trip space for individuals. (2) the other is the commercial service hinterland scale specified by the central place theory 26, i.e., the number of consumers served by different classes and types of commercial clusters varies, creating a hierarchy of different urban centers.
However, there are three deficiencies remaining in the above intra-urban hierarchical structure of activity centers: 1) it does not cover other place communities except urban centers; 2) it lacks the measurement of the spatial scope of intra-urban place communities; and 3) it lacks the in-depth analysis of the causes of the hierarchy of the centers at all levels of the city. Thus, further improvements are made as follows.
(1) Additional two types of typical place communities that are not nodes at the intra-urban centers of any level – the "enclave" type place communities and the "external hub" type are added. Among the 11 types of place communities discussed previously, most of the commercial, public, and office place communities belong to the intra-urban hierarchy of activity centers, except the following two major categories: one is the administrative sub-centers, administrative areas and industrial parks, which have a weak social or economic relationship with intra-urban socio-economic objects, and are generally distributed in large areas like urban residences as a "substrate" for urban functions. The other is the communities formed around external transportation hubs such as airports, high-speed railways, terminals, highway service areas and toll stations.
(2) The second improvement lies in the measurement of various place communities' own spatial scopes, i.e., the spatial distance of economic externalities such as knowledge spillover, and also the spatial distance of shared consumers for commercial communities due to the appropriate scale for residents to walk for leisure.
(3) The fast-changing complex network theory makes it possible for us to explain the reasons to the hierarchical structure of centers at various levels within cities by introducing the concept of nestedness 46. In a network of interacting nodes, nestedness can be described as the tendency for nodes to interact with better-connected ones. The power-law distribution of node properties within nested complex networks in a mature state is explained by various models 47,48. A hierarchical system of intra-urban centers is formed as the nested structure of similar socio-economic complex network by interactions through human flows among nodes 49. These nodes are actually the grids formed by the division of urban built-up areas.
In summary, this paper proposes an improved hierarchical model of intra-urban place communities based on the intra-urban hierarchy model of activity centers (Fig. 6). It sheds light on the spatial characteristics of the hierarchical clustering of intra-urban place communities under the combined effects of biological scale (individual travel spatio-temporal constraints), economic scale (spatial decay law of knowledge spillover and hinterland service scope), and social scale (nestedness characteristics of complex networks).