Introduction

CRPU is a collective term used by the Chinese government to refer to important heritage objects designated for protection. These are immovable relics that are left by human activities from various historical periods with historical, scientific, and cultural value. The protection and utilization of these units have been a key focus of scholars worldwide1. Developed countries began the protection of CRPU early. In 1840, France enacted the Mérimée Law on Historical Monuments, establishing the principle of holistic protection and becoming the first country in the world to legislate for the protection of cultural heritage2. Subsequently, Britain (1882)3, Italy (1909)4 and the Netherlands (1961)5 successively established their own distinctive cultural heritage protection systems. In 1965, the United States proposed establishment of the “World Heritage Trust Fund”, which enforced the protection of cultural heritage through legislation and advocated the common protection of historical relics by all people6. With the deepening of the concept of protection, the international protection system formally established the concept of “cultural routes” in 1994, and incorporated “heritage corridors” into the protection framework in 2008, marking an important shift in the protection of global cultural heritage, from monolithic protection to systematic protection. This marks an important shift in the protection of global cultural heritage from individual protection to systematic protection. China, as one of the four ancient civilizations in the world, has a rich cultural heritage. Although the protection of cultural relics was given high attention by the government, concrete measures were implemented relatively late. In 2002, the Cultural Relics Protection Law was introduced to ensure the scientific protection of relics with outstanding value. The law clarified that important CRPU, including Ancient Sites (AS), Ancient Tombs (AT), Ancient Architecture (AA), Grottoes and Stone Carvings (GSC), Modern Historic Sites and Representative Buildings (MHSRB), Revolutionary Sites, Relics, and Memorial Buildings (RSRMB) and Other (OT) which have vital historic, scientific, and artistic values, should be designated as CRPU at various levels7, designating CRPU as the fundamental units of national cultural heritage protection8. CRPU, which are categorized by their importance into national, provincial, municipal, and county-level designations, the municipal-level and above constitute the core of China’s cultural relics protection system. By 2024, there had been over 5000 national-level CRPUs and more than 26,600 provincial-level CRPUs in China, even with a larger number at the municipal-level. With the continuous national cultural relics survey, the number of newly discovered cultural relics is increasing, and the demand for protection and utilization is huge. However, the existing CRPUs are widely distributed, diverse types, and a lack of systematic protection and utilization, limited by administrative divisions, and are often isolated, so it is difficult to build an open joint system of regional complementarity and symbiosis, which leads to inefficient utilization of resources and affects sustainable development. In a word, countries have changed from paying attention to the concept of a single building to the overall protection strategy of cultural heritage sites, and the overall dynamic protection of regional sites has become the mainstream trend in the field of international heritage protection.

At present, the research on cultural heritage presents a multi-type and multi-scale research trend, but there are obvious limitations. On the research object, scholars mainly focus on individual cultural relics9, traditional villages10, historical blocks11, fortresses12, churches13 and other single-attribute groups or small-scale heritage, and there are few studies on the protection and utilization of concentrated films for hundreds of cultural relics in the same area with complex and diverse types. In terms of research content, scholars combine historical documents to reveal the historical characteristics11, evolution trend2, spatial distribution characteristics14 and development model15 of regional cultural heritage, focusing on the factors affecting the spatial and temporal evolution of cultural heritage, lacking in-depth discussion on the overall value evaluation and collaborative protection mechanism of heritage groups. In terms of research methods, inductive summary method16, historical comparison method9, GIS spatial analysis method17, etc., the research method is mostly qualitative, a small amount of quantitative research, and insufficient methodological innovation. In terms of research scales, macro and micro studies are dominated by exploring the national scale8, the scale of important natural watersheds18, the scale of urban agglomerations19, and individual cultural relics20, with a lack of mesoscale regional level studies. More critically, existing studies have generally neglected the quantitative analysis and network visualization of the internal interactions between cultural heritage clusters, especially the functional associations between heritage nodes at the micro-scale, leading to the contradiction between the systematic protection and adaptive utilization of cultural heritage groups has become even more prominent21. Therefore, breaking through the limitations of traditional research, constructing a scientifical and reasonable ICCUS that transcends simple patchwork of local administration is key to the developing regional collaborative protection.

Qiandongnan, as one of the most well-preserved areas of minority cultures in China, has a long history, has undergone multiple significant historical periods and major historical events, and has survived a large number of cultural relics, ruins, and intangible cultural heritage, it is a model for the protection of China’s cultural heritage and is one of the two World Heritage Site in China, and is one of the world’s 18 original ecological culture protection circles. Its protection and utilization have important demonstrative significance and reference value to the global cultural heritage protection cause. Therefore, this study takes the CRPU in Qiandongnan as the object, adopts Thiessen polygon method and kernel density method to analyze the spatial distribution characteristics and influencing factors of CRPU groups, quantifies the crowd selection paths among CRPUs based on field investigation method and with the help of data crawler, constructs the complex network model between cultural relics protection units based on the topological relationship and with the help of gravity model, and makes quantitative and visualized theoretical analysis on the complex network relationship between cultural relics protection units, and evaluates the development potential based on this. The relationship among overall network, individual network and comprehensive development potential is analyzed by using correlation analysis method, and the internal relationship is analyzed through network structure, and the network structure is regulated based on the internal function relationship of the network and the requirements of upper planning, the ICCUS of CRPU in Qiandongnan is constructed from two parts: spatial structure planning and hierarchical classification planning. Based on the cohesive subgroups to determine the cluster unit, from the mesoscopic scale to realize the scientific nature of protection and utilization, based on the individual network and the comprehensive development potential of specific units (nodes) to determine the development of hierarchical classification, from the microscopic scale to determine the specific development direction of CRPU, which from the scale to ensure the ICCUS of integration and scientific nature. Therefore, the ICCUS of CRPU constructed in this study effectively solves the worldwide problem of “fragmented management” of cultural heritage, promotes the paradigm shift of global cultural heritage protection from monolithic protection to systematic protection, and provides a practical paradigm for the cluster protection of similar cultural heritage, and provides a replicable solution for the systematic protection of the globally dispersed cultural heritage cluster.

Methods

Principles for the selection of research subjects

As an ethnic minority autonomous prefecture in China with the highest number of CRPU, Qiandongnan is both a cluster of Chinese historical and cultural heritage, an ethnic cultural and ecological reserve in China, and a world ecological and cultural heritage protection site. Based on the principles of completeness, originality, historicity, artistry, science, and monumentality (Table 1), the national, provincial, and state and municipal CRPU in Qiandongnan were selected as the research objects.

Table 1 Characteristics of CRPU in Qiandongnan
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Overview of research objects

Qiandongnan is located in the southeast of Guizhou Province, with a ground span of 107 17′ 20″-109 35′ 24″ east longitude and 25 19′ 20″-27 31′ 40″ north latitude (Fig. 1a,b). It borders Huaihua in Hunan Province in the east, Liuzhou and Hechi in Guangxi Zhuang Autonomous Region in the south, Qiannan Buyi and Miao Autonomous Prefecture in the west and Zunyi and Tongren in the north. Qiandongnan has been ruled by Chu since the Warring States Period (5th century BC), and the Han Dynasty strengthened its control and promoted economic and cultural exchanges. During the Tang and Song Dynasties (618-1279), it became a commercial and cultural center, and the Silk Road flourished, promoting ethnic interaction and cultural integration, leaving rich historical sites. During the Ming and Qing Dynasties (1368–1912), the national culture developed further, the cultural integration deepened, and the diverse national cultures were passed down, forming cultural relics such as the wind-rain bridge of the Dong nationality, the Drum Tower and the houses with hanging feet of the Miao nationality. In modern times (1840–1949), after experiencing major historical events such as the Opium War, War of Resistance against Japanese Aggression and the Liberation War, a large number of cultural relics related to resistance activities were kept, and a large number of cultural relics were listed as national and provincial CRPU. Nowadays, there are 20 national-level CRPUs, 99 provincial-level CRPUs and 63 municipal-level CRPUs in this area (Fig. 1c). The types of CRPU include AA, AT, AR, GSC, RSRMB, MHSRB, and OT totaling seven types (Table 2), ranking in the forefront of prefectures and cities at the same level in China, making it an ideal place to study historical and ethnic cultural heritage (Fig. 2).

Fig. 1: Comprehensive Map of the Location of the Study Area and the Grade Distribution of CRPU (Map Source: http://bzdt.ch.mnr.gov.cn/).
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a Location of Guizhou Province in China; b Location of Qiandongnan in Guizhou; c Distribution of Zones Grade of CRPU.

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Fig. 2: Display of some CRPUs in Qiandongnan.
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a Sanmentang Ancient Architectural Cluster; b Longli Ancient Architectural Cluster; c Huangping Old Prefecture Ancient Architectural Cluster; d Langde Shangzhai Ancient Architectural Cluster.

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Table 2 Classification of CRPU in Qiandongnan
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Overall research framework

Using the complex network analysis method to transform the complex and variable relationship of the research object into a visual network structure model, and then based on the network structure model to analyze the relationship between the individual and the overall network, and finally based on the purpose of the research and the requirements of the upper planning to build a centralized and continuous protection and utilization system of CRPU is the basic logic of this research. Numerous research results prove that there is an inherent and inevitable connection between the overall network of the same research object and the individual network and its node attributes22,23,24. The relationship between the overall network and the individual network is manifested in the fact that changes in the structure of the overall network will cause changes in the structure of some of the individual networks; accordingly, changes in the structure of the individual network will also have an impact on the overall network structure. At the same time, the attributes of the network nodes (the attributes of the nodes in this study are the comprehensive development potential of the heritage conservation units) are controlled by the overall network and the individual network, the network controls the performance of the node attributes on the whole, and the optimization of the attributes of all the nodes affects the network morphology and structural characteristics on the whole. Therefore, based on the principles of multidisciplinary, multi-scale and quantitative, this study constructs a more comprehensive and scientific system of concentrated and connected protection and utilization of CRPU, as shown in Fig. 3. The system is able to accurately capture and effectively respond to the complex interactions between the overall network and individual networks, and promote the sustainable protection and adaptive use of cultural heritage as a CRPU.

Fig. 3
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Framework for the Construction of ICCUS.

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Thiessen polygon method

Thiessen polygon (also known as Voronoi), is a result of reflecting the spatial planar section. In this study, Thiessen polygon is used to analyze the spatial distribution type of CRPU. Since the area of Thiessen polygon changes with the distribution of the point set, the coefficient of variation \({Cv}\) value can be used to measure the relative degree of change in the area of the convex polygon, so as to analyze the type of spatial distribution of the sample points25. \({Cv}\) is equal to the standard deviation of Thiessen polygon areas divided by the mean area, and its formula is:

$${\rm{R}}=\sqrt{\sum \frac{{\left({{\rm{s}}}_{{\rm{i}}}-{\rm{s}}\right)}^{2}}{{\rm{n}}}}\,({\rm{i}}=1,2,\cdots ,{\rm{n}})$$
(1)
$${C}_{V}=R/S$$

In the formula: R represents the standard deviation of polygon areas, \({Si}\) denotes the area of the Thiessen polygon, S the average area of the polygons, n stands for the number of polygons. Duvckaerts proposed 3 recommended values to measure the relative degree of change in the region and on this basis categorized the distribution type of the sample points. When the value of \(Cv\, < \,33 \%\), the points are evenly distributed and human factors are the main influence; when \({Cv}=33 \% -64 \%\), the points are randomly distributed and natural factors are the main influence; when the value of \({Cv} > 64 \%\), the points are clustered and natural factors are the main influence26.

Kernel density analysis method

Kernel density analysis calculates the density of point elements or line elements in the surrounding neighborhood, and generates a continuous surface in space from the discretely distributed point data by using a formula, so as to obtain the degree of concentration and distribution of point data in space27. In this study, nuclear density analysis is used to analyze the distribution density relationship of CRPU. The greater the nuclear density value is, the denser the distribution of CRPU, and the calculation formula of nuclear density is28:

$$f(x,y)=\frac{1}{n{\lambda }^{2}}\mathop{\sum }\limits_{i=1}^{n}k/\left(\frac{{d}_{i}}{n}\right)$$
(2)

In the formula (2): n stands for the sample size; λ represents the bandwidth; k is the kernel function; d denotes the spatial distance to sample i; and \(f(x,y)\) is the kernel density estimation value at coordinate point(x,y).

Methodology for evaluating the comprehensive development potential of CRPU

By researching relevant literature and combining field visits to 186 CRPUs in Qiandongnan, the evaluation index system of comprehensive development potential of CRPU in Qiandongnan was constructed after synthesizing the opinions of various parties, and two rounds of Delphi expert consulting method were adopted (8 experts were invited to participate, including 2 experts in cultural heritage protection, 2 experts in regional planning, 2 experts in statistics, and 2 experts in spatial analysis of GIS, who all have the titles of vice high and above titles, with an average of 10 years of experience) to optimize the indicator system, and passed the consistency test of expert opinions (Kendall’s harmony coefficient W = 0.85, p < 0.05). The hierarchical analysis method was adopted to determine the weights of the indicators, and the stability of weight allocation was verified by sensitivity analysis (Spearman rank correlation coefficient>0.92) to form a scientific evaluation system.

$${ADP}=\mathop{\sum }\limits_{i=1}^{n}{X}_{i}\cdot {W}_{i}$$
(3)

In formula (3), \({Xi}\) represents the numerical value computed for indicator i after assignment processing of its original data, \({Wi}\) represents the weight parameter associated with indicator i. ADP denotes the total value of the evaluation index system. A higher ADP value indicates a larger value for either the comprehensive evaluation index system or the development potential evaluation index system of traditional villages, while a lower value indicates the opposite.

Complex network analysis method

Complex network analysis is to simplify the complex system into a collection of nodes and edges connected, the nodes represent the basic units of the complex system, the edges represent the role of the basic units of the inter-relationships29. In this study, the CRPU as “points” and the crowd chooses the path as “line”. and the shortest driving time between CRPUs is calculated through the driving route planning function of Baidu Maps API’s lightweight route planning service. Combined with scholars’ research on commuting time as a quantitative indicator of the strength of attraction links (within 20 minutes is a strong link, and within 30 minutes is a medium link)30. The study took into account factors such as the grade, influence and popularity of the CRPU, as well as the acceptable range of the commuting time of the crowd to the CRPU, and combined with the data from 500 visitor surveys, and the standard of acceptable travel time between the CRPU was determined finally (Table 3). Any two CRPU nodes are reachable within the travel time range, there will be a large number of people choose to commute between these two points, where it is determined that there is a relationship between the two, the relationship matrix is noted 1, and vice versa, 0, and finally the relationship matrix is obtained (Table 4).

Table 3 Acceptable Travel Time between Two Points of CRPU
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Table 4 Matrix Relationship between Two Points of CRPU
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The related indicators of complex network analysis are tools to quantify the characteristics of network structure, which help to understand the relationship between nodes, network connectivity and the efficiency of information dissemination. See Table 5 for specific indicators and definitions.

Table 5 Definitions of Related Indicators of Complex Network Analysis Method
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Correlation analysis method

The SPSS software is used to calculate the comprehensive development potential of the heritage conservation unit, other indicators of the heritage conservation unit and the overall network and individual network structure of the heritage conservation unit, and the statistical analysis is carried out by using the method of correlation coefficient, which accurately reacts to the strength of the linear relationship between the two variables in numerical terms.

Data sources and processing

All data were sourced from the local Cultural Heritage Administration and field surveys. Spatial distribution vector analysis and calculation, visualization of spatial network relationships, and application of the natural breakpoint method through Arc GIS 10.3, statistics and calculations of data through Excel. Hierarchical analysis by yaanp31 to calculate the weights of the evaluation index system of CRPU in Qiandongnan. The shortest driving time between cultural heritage sites was automatically calculated using the Baidu Maps API’s lightweight route planning service. Spatial network structure calculations by Ucinet and correlation calculations by SPSS.

Results

Analysis of spatial distribution of CRPU in Qiandongnan

Through calculation, the standard deviation and average value of Thiessen polygon area are respectively 215.0559 km2, 203.9947 km2, \({Cv}\) value = 105.42%, It shows that the CRPU in Qiandongnan are clustered and the spatial distribution is mainly affected by natural factors. As can be seen from Fig. 4, the spatial distribution of CRPU has the characteristics of “ area-wide distribution and multi-cluster concentration”, and AA and MHSRB are the main types of agglomeration. CRPU is mostly concentrated near river systems and areas with gentle elevation and slope. This choice effectively avoids the potential threat of extreme climatic conditions and geographical environment, and a large number of cultural relics will be produced in natural conditions conducive to crowd gathering, which shows that cultural relics gathering places usually have convenient travel conditions and certain defensiveness. As can be seen from Table 6, AA, AR and MHSRB are spatially clustered. However, AT, GSC revolutionary sites relics and other are randomly distributed in space, and the main influencing factors are natural factors. It also shows that the overall distribution characteristics of CRPU in Qiandongnan are mainly influenced by ancient buildings, AS and MHSRB.

Fig. 4: Coupling analysis between spatial distribution of CRPU and Topography in Qiandongnan.
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(a) Thiessen Polygon Analysis; (b) Kernel density analysis; (c) Geomorphological Analysis; (d) Slope Analysis.

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Table 6 Spatial Distribution of CRPU and Its Influencing Factors
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Evaluation index system of comprehensive development potential of CRPU in Qiandongnan

Integrating the traditional village cultural heritage evaluation framework32, this study adapts and optimizes the indicators for Qiandongnan’s cultural relics, establishing a scientific and practical comprehensive development potential assessment system. Table 7 shows that the comprehensive development potential index system of CRPU in Qiandongnan consists of five first-class indicators: historical and cultural, scientific research, artistic, social and cultural value and comprehensive development environment; and total 12 second-class indicators such as popularity and influence, completeness, longevity and research degree. Among the primary indicators, the historical and cultural value (0.36) of CRPU is the highest, followed by scientific research value (0.25), artistic value (0.18), social culture (0.14) and comprehensive development environment (0.07); among the secondary indicators, those with higher weight of CRPU include scientific and technological level (0.15), longevity (0.13), popularity and influence (0.12), completeness (0.11) and rarity (0.11). It shows that the level of science and technology, longevity, popularity and influence, completeness and rarity are important components of the comprehensive development potential of CRPU.

Table 7 Evaluation Index System of Comprehensive Development Potential of CRPU
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Network model and spatial relationship of CRPU in Qiandongnan

Figure 5 shows that the network structure of CRPU in Qiandongnan as a whole is a parallel structure of multiple clusters, and the size of the clusters varies, and the contact between the groups is weak through individual CRPU. There are 13 unconnected orphaned CRPUs in the area and 1 isolated grouping.

Fig. 5
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Network structure Model of CRPU in Qiandongnan.

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Figure 6 shows that the geographical distribution characteristics of CRPU in Qiandongnan is the main reasons for the different sizes of network groups, and there are widespread connections among CRPU that cross administrative boundaries, which further proves that the regional development of CRPU should not be restricted or separated by artificial administrative boundaries.

Fig. 6
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Spatial Contact Relationship of CRPU in Qiandongnan.

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Analysis of the overall structure of the network of CRPU in Qiandongnan

Figure 7a shows that the CRPU in Qiandongnan have three levels and eight groups of cohesion of subgroups, and the sub-groups are different in size, among which every two closely related groups can form four groups in the second level. Figure 7b shows that the third-level subgroups belonging to a second-level are geographically adjacent. The types of CRPU in Qiandongnan have little influence on the relationship between their subgroups, ___location and internal connections are the main influencing factors.

Fig. 7: Integrated analysis of network subgroups and spatial distribution of CRPU in Qiandongnan.
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(a) Calculation Results of the Cohesive-Subgroups of the Network of CRPU; (b)Distribution of Cohesive-Subgroups of the Network of CRPU.

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Figure 8 shows that the core-periphery structure is obvious in the overall structure, and the core node is usually the center of the network grouping. Comparison of Fig. 10 shows that the core nodes are located in subgroups 4, 5, 6, 7 and 8 areas, which reflects the uneven distribution of the regional cultural core display nodes and the clustering nature of important cultural heritage. The types of CRPU in the core nodes are mainly AA and MHSRB (accounting for 84.93%), This reflects that AA and MHSRB is important carriers for displaying regional culture to the outside world. Moreover, the number of core nodes of MHSRB accounts for a higher proportion (accounting for 55.36%), which shows that MHSRB is more useful to become the center of regional networks.

Fig. 8
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Calculation Results of Core-periphery Structure of Network of CRPU.

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Fig. 9
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K-core Distribution of the Network of CRPU.

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Network stability analysis of CRPU in Qiandongnan

As can be seen from Fig. 9, there are 73 K cores with an average value of more than 7.3, accounting for 39.25% of the whole network, and the types of cultural relic protection units are mainly modern and important historical sites (accounting for 55.36% of their own types), indicating that the stability of the overall network is poor. The protection units of MHSRB can effectively interact with other protection units in the network, showing stronger stability; The size of K-core has the characteristics of regional distribution, and the same K-core gather nearby, which has the process of high-K-core settlement spreading to low-K-core settlement.

Fig. 10
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Distribution of Network Degree Centrality of CRPU.

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Analysis of network completeness of CRPU in Qiandongnan

In the network relationship of CRPU in Qiandongnan, the network density is 0.0591; the spatial network density is lower; the network organization is looser; the average distance of the network is 4.045 and the inter-network connectivity is average; the agglomeration coefficient is large (0.738); the small-world character of the network structure is not obvious, and the overall network completeness is poor.

Analysis of network balance of CRPU in Qiandongnan

The network center potential of CRPU in Qiandongnan is 12.06%, and the network balance is weak. Figure 10 shows that the nodes with higher degree center values are unevenly distributed in each cluster, mainly in the northwest and southeast, indicating that the network structure of the northwest and southeast clusters is more dense. And the types of these nodes are mainly AA and MHSRB, which shows that AA and MHSRB are more suitable for the utilization and development under the background of contemporary society.

Network vulnerability analysis of CRPU in Qiandongnan

As shown in Fig. 11, there are 8 cut-point in the network relationship, accounting for 4.30% of the network, and the maximum point of cut-point effect is No.94, which can affect at most 19 CRPUs to lose contact with the whole network. The types of CRPU are mainly AS (accounting for 14.29% of their own types) and MHSRB (accounting for 5.36% of their own types); this indicates that the overall network is less vulnerable, but the cut-point are more influential and the nodes where the type of CRPU is an ancient site are more cohesive. It can be seen that the cut-point is a key county with obvious transportation advantages, indicating that the type of CRPU and the transportation conditions in which it is located are the key influencing factors for the cut-point.

Fig. 11
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Cut-point Position of CRPU in Qiandongnan.

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Individuals competitive analysis of network of CRPU in Qiandongnan

Figure 12 shows that there are 33 CRPUs with higher competitiveness and above, which are distributed in the center of the cluster with high concentration of CRPU and are not limited to a certain area, but are connected with many surrounding CRPUs, accounting for 17.74% of the overall network. And the types of CRPU are mainly ancient buildings (accounting for 21.95% of their own types) and MHSRB (accounting for 21.43% of their own types). It shows that the agglomeration of CRPU is conducive to improving the competitiveness of CRPU. The overall network competitiveness of Qiandongnan is poor, and the type of CRPU is ancient buildings have more competitive advantages in individual networks.

Fig. 12
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Distribution of Individual Network Competitiveness of CRPU in Qiandongnan.

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Analysis of the individual nature of the network of CRPU in Qiandongnan

Figure 13a shows that there are 20 CRPUs with higher and above network coordinator function roles, accounting for 10.75% of the overall network, and the types of CRPU is mainly based on AA (10.98% of its own type) and MHSRB (17.86% of its own type), mainly distributed in the northwest and southeast of Qiandongnan, distributed in 4, 5, 6, 7 four subgroups (Fig. 7). It indicates that CRPU of MHSRB has a strong information dissemination ability in the network, more conducive to promote the exchange between the nodes, and these four subgroups all have high-impact CRPU on the logistics and information flow in their own subgroup networks.

Fig. 13: Spatial distribution of individual network roles for CRPU in Qiandongnan.
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(a) Distribution of the Role of “Coordinator” in the Individual Network in Qiandongnan; (b) Distribution of the Roles of “Goalkeeper” and “Representatives” in the Individual Network; (c) The Role Distribution of Individual Network “Consultant” in Qiandongnan; (d)Distribution of roles of “Liaison” of Individual Networks.

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Figure 13b shows that in this study, the functions of gatekeepers and representatives are the same, and there are 17 CRPUs with higher or higher functions of gatekeepers and representatives, accounting for 9.14% of the total network, and the number is small, and the types of CRPU are mainly AS (accounting for 14.29% of their own types), comparison of Fig. 7 reveals its distribution in subgroups 5, 6, and 7. It shows that these subgroups become the core areas of the overall network because there are CRPUs with strong information connection inside and outside the subgroups, and AS can better reflect the information connection ability of CRPU from point to point.

As shown in Fig. 13c, there are three CRPUs with higher and above consultant functions, accounting for 1.16% of the whole network; the number is small, and the types of CRPU is mainly other (accounting for 11.11% of their own types). Compared with Fig. 7, it is found that these nodes are distributed in subgroup 5. Although these nodes can not strengthen their own subgroup contact, they are beneficial to contact with and strengthen the external subgroup contact. It shows that the nodes with other types of cultural relic protection units can maintain better connections with external stakeholders of subgroups and strengthen the connections among related subgroups.

As can be seen from Fig. 13d, there are 2 cultural relic protection units with a high or higher liaison role, a very small number, accounting for 1.08% of the overall network, and the types of cultural relic protection units are mainly other types (accounting for 11.11% of their own types), 79.03% of the CRPU does not have the function of liaison, and 19.89% does not have a significant liaison function. This phenomenon reveals the scarcity of nodes that can act as independent third-party forces to influence or limit the communication and resource flow between different subgroups. It shows that the overall network structure does not rely too much on a few key nodes to maintain its connectivity, thus showing low vulnerability. It also reflects that other types of CRPU is more conducive to enhancing the community cohesion of CRPU and promoting exchanges and mutual assistance between CRPUs.

Analysis of comprehensive development potential of CRPU in Qiandongnan

Figure 14 shows that compared with the geographical ___location, the regional distribution of CRPU with higher comprehensive development potential is relatively balanced, while the distribution of CRPU with lower development potential is more dispersed, indicating that the existing CRPU are unevenly developed, underutilized and their utilization does not match their own conditions. However, the comprehensive development potential of CRPU in the center of the network is usually better, which reveals that the CRPU with higher comprehensive development potential has a better network ___location. At the same time, there are 76 CRPUs with higher or above comprehensive development potential, accounting for 40.86% of the overall network, and the types of CRPU is mainly ancient buildings (accounting for 73.17% of their own types) and AS (accounting for 71.43% of their own types). It shows that AA and sites are the carriers of historical and cultural dissemination and display. Meanwhile, the development and utilization of ancient buildings are more in line with the social background and economic development needs, and the comprehensive development potential of CRPU in Qiandongnan is better.

Fig. 14
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Spatial distribution of comprehensive development potential in Qiandongnan.

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Relationship between comprehensive development potential and network structure of CRPU in Qiandongnan

As can be seen from Fig. 15a, the comprehensive development potential of CRPU, the overall network of CRPU, and the individual network of CRPU is pairwise correlated; the comprehensive development potential is highly positively correlated with the competitiveness of the individual network and the functional role of the network, indicating that the comprehensive development potential of the CRPU can be increased by improving its competitiveness and functional role in the network; the comprehensive development potential has a positive correlation with K-core, core-periphery structure and degree centrality in the overall network relationship, which shows that the overall development potential can be increased by improving the stability, completeness and balance of the overall network.

Fig. 15: Correlations among comprehensive development potential, component factors, and network structure of CRPU in Qiandongnan.
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a Relationship between Comprehensive Development Potential Value and Network Structure. b Relationship between Elements of Comprehensive Development Potential and Network Structure (note: Coo: Coordinator; Gat: Gatekeeper; Rep: Representative; Consul: Consultant; Lia: Liaison; Effe: Effective size of the network; Effi: Efficiency; Constr: Constraint; K-c: K-core; C-p: Core-periphery; Dc: Degree centrality; Cs: Cohesive subgroups; Cut: Cut-point; Hcv: Historical and cultural value; Srv: Scientific research value; Av: Artistic value; Scv: Social and cultural value; Cde: Comprehensive development environment; Alt: Altitude; Slo: Slope; Asp: Aspect.). **At the 0.0 l level (two tailed), the correlation is significant. * At the 0.05 level (two-tailed), the correlation is significant.

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Figure 15b shows that in the network structure of CRPU in Qiandongnan, historical and cultural value is an important factor affecting the overall network and individual network of CRPU in Qiandongnan. The higher the historical and cultural value is, the higher the effective scale is and the smaller the limitations in the individual network is, the more obvious the competitiveness is. The more times the CRPU plays a functional role, the higher the comprehensive development potential is, and the stronger the stability, completeness and balance in the overall network is. Slope is the second influential factor. The greater the slope is, the greater the relief is, the lower the effective scale in the individual network is, the higher the limitation is, the weaker the competitiveness is, the fewer the number of functional roles is, the lower the comprehensive development potential is, and the weaker the stability, completeness and balance is in the overall network. The comprehensive development environment, altitude and artistic value are weak influencing factors, and the comprehensive development environment is highly positively correlated with the effective scale in the individual network, the number of times of acting as a “goalkeeper” and “representatives”, and the K-core and degree centrality in the whole network.

Protection and development planning of CRPU in Qiandongnan based on the ICCUS

From the above, it can be seen that the cluster distribution of CRPU in Qiandongnan is significant, and the stability, completeness and balance of the overall network are positively correlated with the comprehensive development potential of CRPU, the competitiveness of nodes in the individual network and their functional roles. The overall network structure has a regulating effect on the competition, function role and comprehensive development potential of the individual network of CRPU. Therefore, based on the spatial layout characteristics of current CRPU and the needs of upper planning, it emphasizes the coordinated development of points with lines and lines with surfaces. By adjusting the network structure to enhance the regional development potential, planning the regional protection of CRPU to optimize the allocation of resources, and implementing the classification protection strategy, from macro to micro, comprehensively and accurately protect each level and each type of CRPU, which gradually builds a concentrated and connected protection and utilization system, improving the level of protection, and promote the sustainable development of regional synergy of CRPU.

Spatial structure delineation of conservation and development of CRPU in Qiandongnan

Based on the characteristics of the current network relationship, the cluster unit of regional CRPU is delimited. Cluster units are divided based on the distribution characteristics of cohesive subgroups in the network structure, combined with administrative requirements, regional geography, functional relationships, upper planning and future development trends. Important nodes for regional development are defined according to the importance of network nodes in individual networks, and considering the functional roles, competitiveness, comprehensive development potential and regional balance requirements of nodes. Combining entropy weight calculation and double threshold judgment (topology > 0.4 and function > 0.6), it is ensured that the selection of core nodes not only conforms to the network structure characteristics, but also meets the needs of regional balanced development.

As shown in Fig. 16a: the protection and development cluster units in the centralized contiguous area of CRPUs are divided into 8 cluster units according to the cohesive subgroups, management scale and administrative boundaries. Compared with the 16 independent administrative areas divided into cities and counties, the design of this unit significantly promotes the collaborative cooperation and mutual assistance development among cultural heritage protection groups, and provides a more efficient and close framework for the protection and inheritance of cultural heritage.

Fig. 16: Comprehensive plan for the management and functional structure of the cluster of CRPU in Qiandongnan.
figure 16

(a) Division of Cluster Management Units of CRPU in Qiandongnan; (b) Functional Structure Planning of CRPU in Qiandongnan.

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As shown in Fig. 16b: according to core-periphery, upper planning and current resource distribution, 8 cluster units will be divided into core driving areas (core area of network structure, high overall development potential), core development areas (more core nodes, higher overall development potential), and general development areas (weak stability of network structure, average overall development potential); according to the ranking of individual competitiveness and ___location requirements of CRPU, 14 CRPUs are designated as important nodes of the cluster, and 7 CRPUs with high functional value are selected as important nodes of the region, which conforms to the development of existing advantageous CRPU and strengthens the external connection function of the CRPU cluster.

Planning and upgrading of CRPU in Qiandongnan

Key CRPU needs to enhance their competitiveness and role functionality, and enhance their development potential by enhancing their historical and cultural values. The promotion of comprehensive development potential of key CRPU will inevitably enhance the importance of their individual networks, and then promote the overall network with the promotion of individual networks, so as to ensure the continuous improvement of comprehensive development potential of CRPU.

On the whole, by optimizing traffic and increasing network connectivity (average distance between networks), its network stability (K-core values) and completeness (degree centrality) are improved, and its development potential is enhanced for important nodes.

Through the above measures, the planning scheme is verified, and it is found that the overall network density is changed from 0.0591 to 0.1821, the average distance between networks is changed from 4.045 to 2.230, the overall network connectivity is greatly improved, and the number of K-core values higher than 12 increased from 22.58% to 79.03%, and the stability is enhanced. The degree centrality increased from 12.16% to 31.32%, indicating enhanced balance.

Classified protection and classified development of CRPU in Qiandongnan

This study systematically analyzes the management mode of CRPU by adopting the method of combining graded protection and classified development. The two complement each other: graded protection clarifies the protection priority, classified development highlights the functional positioning, and jointly promotes the sustainable use of cultural relics and the coordinated development of the region.

Table 8 shows that there are three levels of protection according to the level of CRPU (national, provincial, state and municipal), with the first level of protection being the strongest and the third level the weakest.

Table 8 Protection Levels and Measures
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As shown in Table 9, CRPU plays a key role in the protection and inheritance of cultural heritage. According to the historical and cultural value, scientific research value, artistic value and social and cultural value of each CRPU, the CRPU is divided into three categories: protection and research type, exhibition and education type and cultural tourism and business type. For the protection of key cultural relics, we should deeply explore and grasp their resource advantages, clarify the development direction, and actively play a leading and driving role by strengthening the ties with other cultural relics protection in industry and culture, so as to promote the overall development of the region. For the general protection of cultural relics, it focuses on the protection, renovation, display and utilization of cultural relics, so as to improve the infrastructure level of CRPU and promote the process of their classified development.

Table 9 Development Classification of CRPU in Qiandongnan
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Discussion

This study found that the CRPU in Qiandongnan showed a significant spatial distribution characteristics, which was consistent with the spatial distribution pattern of CRPU in the Yellow River Basin18. This phenomenon further shows that the distribution of cultural relics is mainly affected by population activities, rather than geographical differences between the north and the south. It is natural conditions and cultural agglomeration that are the main reasons for cultural relics agglomeration. It is easier to form a gathering area of CRPU near the river system and in areas with gentle elevation and slope. The study indicates that the CRPU above the municipal level in Qiandongnan are dominated by AA and have diversified characteristics, which is in line with the distribution pattern of the national key CRPU in the Yangtze River Delta14. However, this study also found that the distribution of AA in Qiandongnan is denser, which may be related to the historical development pattern of the local ethnic minority settlements. This study uses social network analysis method to reveal that the network of CRPU in Qiandongnan is characterized by structural imbalance, low network density and poor stability. This result is partially consistent with the findings of rural settlement networks in small watersheds in hilly and gully areas of China Loess Plateau33, which is mainly attributed to the complexity of the karst landscape and the variability of the plateau landscape, further reflecting that the distribution is closely related to the geographic environment. At the same time, the study also found that cultural relics are mostly concentrated along rivers and in gentle areas, a distribution pattern that not only avoids environmental risks, but also meets the transportation and defense needs required for settlement, fully reflecting the intrinsic correlation between the distribution of cultural heritage and livable natural conditions. In addition, unlike foreign studies on fortress clusters34,35, the small-world characteristics of CRPU in Qiandongnan are not obvious, and the connectivity between nodes is low. This is mainly due to the complex terrain in Qiandongnan and the large elevation gap between CRPU, which makes contact more difficult. Moreover, the CRPU in Qiandongnan are mainly ancient buildings, most of which are residential gathering points, and the contact demand is low, which is in sharp contrast with the defensive characteristics of the fortress group. This study also found that there is a significant positive correlation between the overall network of CRPU, individual networks and comprehensive development potential. This result is consistent with Zou Huijun’s study on the network relationship of village clusters36, the higher the integrated quality of a node, the more it can play a radiation-driven role for other nodes. In addition, the study also found that the overall network morphological structure can exert a moderating effect on individual networks, and the functional role nature of individual networks can also reflect some of the characteristics of the overall network. Scholars have found that network relationships are not blocked by administrative boundaries by sorting out relationships within village clusters37, the phenomenon also exists in this study. This suggests that the management of CRPU should not be limited by administrative boundaries, but should be planned in an integrated manner based on their functional attributes and network relationships. Some scholars have proposed that attention should be paid to the cultivation of functional zoning and important nodes based on the development of regional village and town systems38, which is supported by this study.

This study systematically analyzes the spatial distribution, network structure and comprehensive development potential of CRPU in Qiandongnan, revealing their unique spatial characteristics and internal relationships. The following are the main findings of this study: (1) Spatial distribution characteristics: CRPU in Qiandongnan are characterized by the cluster distribution of “area-wide distribution and multi-cluster concentration”, and natural factors are its main influencing factors. (2) Network structure characteristics: Qiandongnan CRPU network relationship is a multi-group parallel structure, there are three levels and eight cohesive subgroups of multi-level relationship, the core-edge structure is obvious. Regional and internal connections are the main determinants of subgroup attributes, and the MHSRB of CRPU are more likely to become the core nodes of the network. The network is less stable, complete, balanced, and vulnerable. (3) Comprehensive development potential: the comprehensive development potential, the overall network and the individual network of the CRPU are positively correlated, and the historical and cultural value is its main influence factors. Nodes with high competitiveness and role functions occupy an important position in the individual network, and the overall comprehensive development potential is average. The above findings have enriched the theoretical research in the field of cultural heritage protection, especially in the research on the internal relationship of heritage protection units, systematically revealing the characteristics of their spatial distribution and network structure, providing a theoretical basis for regulating the network relationship and promoting the development of the heritage protection units, and providing a new perspective for identifying the core-periphery structure. Based on these findings, this study establishes the ICCUS framework for Qiandongnan’s CRPU through a systematic process: identifying spatial distribution patterns, analyzing network structures, examining development relationships, delineating spatial organization, positioning individual units, and formulating tiered development strategies. This approach enables coordinated management from macro-level planning to individual conservation, offering an operational framework and theoretical foundation for heritage protection in Qiandongnan and similar regions while fostering cross-regional collaboration and sustainable development.

However, this study has limitations: (1) The scarcity of historical data, especially for below municipal-level units, may lead to incomplete results and network structure bias. (2) Neglecting spatiotemporal evolution limits the reflection of dynamic historical changes and long-term trends, affecting conclusion accuracy. Future research should incorporate dynamic development analysis, improve indicators, expand scope, and employ remote sensing/big data to quantify influencing factors for more comprehensive and precise results.

Fig. 17
figure 17

Schematic Diagram of Broker Roles.

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