Spatio-temporal evolution characteristics of cultural heritage sites and their relationship with natural and cultural environment in the northern Fujian, China

China’s northern Fujian, as one of the spatial carriers of renowned traditional Chinese cultures such as Minyue, Zhu Xi’s Neo-Confucianism, tea, and porcelain, has preserved a wealth of tangible cultural relics, showcasing a profound cultural heritage and possessing strong research value and development potential. This study employs GIS spatial statistical analysis and map visualization technology to unveil the evolutionary processes of cultural heritage sites in northern Fujian, focusing on their spatial types, forms, and densities across different historical periods. Based on this foundation, the research further delves into the intrinsic relationships between the spatial distribution characteristics of cultural heritage sites in northern Fujian during various historical periods and the local natural and cultural environment. The results indicate that: (1) the spatial distribution of cultural heritage sites in northern Fujian varies across different historical periods, with the highest concentration and quantity observed during the Ming and Qing periods. In contrast, the Qin, Han, Wei, Jin, Northern and Southern Dynasties period exhibits the lowest quantity and a more dispersed distribution. (2) Cultural heritage sites in northern Fujian are mainly distributed in the relatively flat terrain below 400 m above sea level, including middle to low-altitude mountain basins, river valleys, and low hills. In terms of distance from rivers, cultural heritage sites exhibit a clear distribution pattern along rivers, with a large number of them located within 0–6 km from the riverbanks. (3) The spatial distribution of cultural heritage sites in northern Fujian is influenced not only by macro-environmental factors such as topography, altitude, and rivers but also by micro-shaping from social and cultural elements like Minyue culture, tea and porcelain ancient road culture, Zhu Xi’s Neo-Confucianism culture, religious beliefs and customs culture, and red revolutionary culture across different historical periods. This study contributes to the establishment of a model correlating cultural heritage sites with historical periods and provides an interdisciplinary methodological framework to understand the relationship between cultural heritage sites and the geographical environment.


Introduction
Cultural heritage sites, as cultural products of specific historical periods, not only reflect the evolutionary processes of cultural forms and the natural environment within a certain timeframe but also bear witness to the rise and fall of a nation, ethnicity, and region throughout history [1].Since the issuance of the "The Athens Charter" [2], international organizations, primarily led by the International Council on Monuments and Sites and the International Centre for the Study of the Preservation and Restoration of Cultural Property, have promulgated a series of charters and conventions.The promulgation of these international protection documents emphasizes the significance of cultural heritage sites within the cultural heritage conservation system.They establish various requirements at different levels regarding the definition and hierarchy of "protection, " as well as the aspects of ideology and spirit, principles and methods, policies and management, strategies and means, procedures, and more [3].Correspondingly, countries worldwide have undergone extensive exploration in the protection of cultural heritage sites, establishing comprehensive legal frameworks and management institutions in practice.France, being the first country globally to legislatively protect cultural heritage sites, enacted the "Mérimée Law on the Historical Monuments" in 1840, outlining the principle of holistic protection [4].The United States, as the pioneer of the global national park system, set a precedent for the protection of cultural heritage sites within national parks [5].They introduced the concept of heritage corridors, defining this novel protection method from the perspectives of resources and values and emphasizing the role of human activities in the formation of national landscapes [6].China's cultural heritage site protection system has also undergone a process of gradual improvement.The promulgation of the "Law of the People's Republic of China on Protection of Cultural Relics" in 1982 marked the formal establishment of China's cultural relic protection and management system [7].In 2014, the Ministry of Housing and Urban-Rural Development of the People's Republic of China issued the "Regulations on the Compilation and Approval of Protection Plans for Historic and Cultural Cities, Towns, Villages, and Blocks", emphasizing the integrity and authenticity of cultural heritage site protection [8].In summary, countries globally have transitioned from a focus on individual architectural concepts to holistic protection strategies for cultural heritage sites.Regional site protection and the overall dynamic protection of the cultural and natural aspects have become the mainstream trends in the field of international heritage protection.
From an academic standpoint, the perspective on cultural heritage sites has transitioned from the traditional focus on individual historical and cultural resources to encompass regional historical and cultural space.This shift is not a mere conceptual enlargement or what is commonly referred to as generalization.Instead, it is grounded in several crucial theoretical foundations that have gradually developed since the twentieth century, prompting numerous scholars to conduct research in this area.Firstly, cultural geography interprets the structuralism of modern historical geography used in territorial space [9].Scholars, combining historical literature, aim to reveal the historical characteristics [10], evolutionary trends [11], and cultural meme [12] of regional cultural heritage.They explore historical and human factors such as commerce, policies, and management systems that influence the spatiotemporal evolution of cultural heritage [13].Secondly, ecological geography [14] focuses on characterizing [15], simulating, and predicting [16] the spatial landscape imagery [17], spatial distribution features [18], and developmental patterns [19] of cultural heritage.It explores the interaction between cultural and natural, social-related factors such as altitude, water systems [20], land use types [21], ethnic distribution [22], policy support, population density [19], and the symbiotic relationships among various internal factors.Thirdly, digital geography emphasizes regional protection theories such as linear cultural heritage [23], cultural routes [24], heritage corridors [25], and national parks [26].Leveraging technologies such as GIS [27], Terrestrial Laser Scanning (TLS) [28], and Computer programming [29], researchers explore monitoring and early warning [30], 3D modeling [31], virtual reality [32], and spatial and digital conservation strategies [33] for regional cultural heritage.These studies provide crucial theoretical and methodological support for understanding the human-environment interaction forming regional systems in the realm of cultural heritage.It is worth noting that fewer studies directly focus on cultural heritage sites but rather incorporate them into the analysis within the framework of cultural heritage systems.Meanwhile, existing research tends to concentrate on the interactions between natural and social elements and provides analyses from a humanistic historical perspective.However, these studies often overlook the interconnected relationships between natural ecological factors and the historical-cultural developments.Culture, as it emerges and evolves within specific socio-economic contexts, intertwined with both natural and human geographical environments, embodies three fundamental elements: human communities, historical conditions, and geographical settings, reflecting distinct ethnic, temporal, and regional characteristics.By positioning cultural heritage sites within a multidimensional framework encompassing nature, society, and history, it becomes possible to comprehensively elucidate their characteristics, origins, and patterns, facilitating the formulation of more scientifically grounded holistic preservation strategies.
This study selects the northern Fujian region of China as a case study area.Dating back to the Neolithic Age, this area has served as a habitat for ancient humans, maintaining active socio-economic activities throughout its extensive historical evolution.During the Xia, Shang, and Zhou periods, it emerged as a significant territory among the Seven States of Min, later becoming part of the territory of King Goujian of Yue during the Warring States period.Subsequently, it developed maritime Silk Road trade, exerting broad influence both domestically and internationally.With a profound cultural heritage, the region is replete with numerous cultural relics, including the globally renowned UNESCO World Cultural and Natural Heritage Site, Mount Wuyi, and the birthplace and development site of the renowned Confucian ideology, Zhu Xi's Neo-Confucianism.The extensive historical and cultural legacy, flourishing commerce, and diverse culture make northern Fujian a compelling testament to Chinese and global cultural richness.This extensive historical and cultural heritage has left behind a plethora of tangible cultural relics within the northern Fujian region, bearing rich historical, cultural, and humanistic values.These sites are of significant importance for comprehending and researching the social, political, economic, and cultural aspects of northern Fujian during historical periods.Therefore, this research employs GIS spatial analysis methods to reveal the evolutionary processes of spatial types, forms, and densities of cultural heritage sites in northern Fujian across different historical periods.Building upon this foundation, the study further analyzes the inherent relationships between the spatial distribution characteristics of cultural heritage sites in northern Fujian during various historical periods and the local natural and cultural environment.This study contributes to the establishment of a model correlating cultural heritage sites with historical periods and provides an interdisciplinary methodological framework to understand the relationship between cultural heritage sites and the geographical environment.
The primary research objectives of this study include the following three points:

Study area
The northern region of Fujian, China (117° 00′-119° 17′ E, 26° 15′-28° 19′ N), is comprised entirely of Nanping City, Fujian Province, with an area of 26,300 square kilometers (Fig. 1).The area features widespread low hills and ridges, interspersed with valleys and small basins among the mountains, showcasing the typical Fujian landscape characterized by "80% mountains, 10% water, and 10% fields".In ancient times, the region was densely covered with mountains and forests, with a warm and humid climate and abundant snakes and insects.The short name of Fujian is "Min (闽)".The term "Min" refers to the clan that worshipped snake deities.Even today, many Snake King temples still exist in northern Fujian, preserving the customs of shamanistic worship and totem reverence from the Minyue culture.During the Sui, Tang, and Five Dynasties periods, the northern Fujian region served as the location of the ancient Jianzhou, one of the earliest developed areas in Fujian.The name "Fujian" is derived from the initials of the ancient Fuzhou and Jianzhou.In the 32nd year of the Shaoxing period of the Song Dynasty (1162 A.D.), the northern Fujian region was reorganized into Jianning Prefecture, marking the earliest establishment of a prefecture in Fujian's history and earning the title of "the capital of the Eight Min".Additionally, the northern Fujian region is recognized as the birthplace and flourishing center of Zhu Xi's Neo-Confucianism, earning the honorary titles of "Zoulu of Fujian" and "Southern Sanctuary of Daoist Philosophy".

Methods
Based on the scale of the study area and the attribute characteristics of spatial data, in order to accurately and effectively reveal the spatial distribution patterns, clustering features, and evolution rules of cultural heritage sites in the northern Fujian region during various historical periods, the analytical method system of this study is as follows.

Average nearest neighbor
The Average Nearest Neighbor (ANN) analysis is employed to reflect the spatial clustering patterns of point features by comparing the actual nearest neighbor distance among features within the spatial range with the theoretical nearest neighbor distance [34].The formula is as follows: where A represents the area of the research region; n is the sample size; r E denotes the theoretical nearest neighbor distance; r I is the actual spatial nearest neighbor distance; R stands for the nearest neighbor index.
Based on the value of R, the spatial distribution level of the research samples within the area can be determined: random distribution (R = 1); clustered distribution (R < 1); dispersed distribution (R > 1).

Voronoi diagram analysis
The Voronoi diagram, also known as Thiessen polygons, is a method used for plane partitioning.Specifically, it represents that for any arbitrary convex polygon, the distance from any point within that convex polygon to (1) (2) R = r I / r E , its controlling point is smaller than the distance to any other controlling point [35].In this study, the coefficient of variation CV from the Voronoi diagram is employed to further validate the distribution pattern of cultural heritage sites.The calculation formula is as follows: where CV represents the coefficient of variation, indicating the ratio of the standard deviation of Voronoi polygon areas to their mean.When CV < 0.33, it indicates a uniform distribution of sample points; when 0.33 ≤ CV ≤ 0.64, it indicates a random distribution of sample points, and when CV > 0.64, it suggests an aggregated distribution of sample points.

Standard deviational ellipse
The Standard Deviational Ellipse (SDE) is an effective spatial statistical method capable of precisely revealing the overall characteristics of the spatial distribution of geographic features [36].The center of the SDE (3) CV = Std Ave × 100%, Fig. 1 The location of northern Fujian corresponds to the spatial distribution centroid of cultural heritage site features.The major axis and minor axis represent the main and sub-trend directions of the spatial distribution of features, respectively.The lengths of the major and minor axes indicate the extent to which feature spatial distribution deviates from the centroid in the main and sub-trend directions [37,38].The oblateness, which is the ratio of the difference between the major and minor axes to the length of the major axis, reflects the morphological characteristics of feature spatial distribution.The rotation is the angle between the true north direction and the major axis rotated clockwise, representing the main direction of point spatial distribution.The formula is as follows: where M X, Y represents the mean center coordinates; θ is the azimuth angle of the ellipse; x i , y i are the spatial coordinates of the point features.

Kernel density estimation
The Kernel Density Estimation (KDE) is a non-parametric estimation method for analyzing the density of geographic features in the surrounding area.It involves assigning different weights to sample points within the research area using a kernel function, resulting in a smoother density map that reveals the density attributes of the unknown area [39].The calculation formula is as follows: where f(x,y) is the density estimate value at the location (x,y); n is the number of observations; h is the bandwidth; k is the kernel function; d i is the distance between a location in the study area and the i-th observation location [40].After calculating the kernel density results, this study further reclassifies the original kernel density values of cultural heritage sites for each historical period using the Jenks natural breaks method.The reclassification involves five levels, ordered from low to high kernel density values: Level five, Level four, Level three, Level two, and Level one.).Some of the cultural relics protection units experienced multiple Dynasties, such as the Jianyao site experienced Tang and Song periods, so when counting the number of cultural relics protection units, the cultural relics protection units are counted as two and classified into Sui, Tang, and Five Dynasties period and Song and Yuan period respectively.Hence, based on the dynastic classification, the total number of cultural relics protection units studied in this paper is 678, serving as the foundational data for this research.The Baidu coordinate retrieval system was utilized to obtain the spatial coordinates of each cultural heritage site.Following the acquisition of the coordinates, historical period cultural heritage sites' spatiotemporal evolution characteristics were explored using methods like average nearest neighbor analysis, standard deviational ellipse, and kernel density estimation.
To further investigate the relationship between the spatiotemporal evolution characteristics of cultural heritage sites and the natural environment and human socio-cultural activities, several steps were taken.Initially, 30 m resolution DEM elevation data for the northern Fujian region were obtained through cloud-based geographic spatial data.Subsequently, employing ArcGIS software, the coordinates of cultural relics protection units for each period in the northern Fujian region were visualized.Then, distribution maps of cultural heritage sites for various historical periods were created on topographical maps stratified by elevation in the northern Fujian region.Lastly, tools such as reclassification and Euclidean distance in ArcGIS were used to analyze and calculate factors like elevation and distance from rivers for cultural heritage units in different historical periods.Coupled with the primary socio-cultural background of cultural heritage sites in each period, this analysis aimed to explore the spatiotemporal distribution characteristics of cultural heritage sites in the historical periods of northern Fujian and their relationship with the human-environment system.The analytical framework of this study is illustrated in Fig. 2.

The evolution of spatial types
This study employed the method of Average Nearest Neighbor analysis to identify the spatial characteristics of cultural heritage sites in northern Fujian during six historical periods, as presented in Table 1.Among them, the spatial structure types of the Prehistoric and Pre-Qin period, Sui, Tang, and Five Dynasties period, Song and Yuan period, Ming and Qing period, and Modern era exhibit a clustered distribution, with the clustering magnitude ranking as follows: Ming and Qing period > Prehistoric and Pre-Qin period > Song and Yuan period > Modern era > Sui, Tang, and Five Dynasties period.Throughout all historical periods, only the spatial structure type of the Qin, Han, Wei, Jin, Northern and Southern Dynasties period is characterized by a dispersed distribution, which is significantly associated with the lower quantity of cultural heritage sites during that period.
Furthermore, through Voronoi analysis, we obtained Voronoi polygon maps depicting the spatial distribution of cultural heritage sites across different historical periods (Fig. 3), along with their coefficients of variation (CV).The CV values further corroborated the results of the average nearest neighbor analysis.The CV value for the Qin, Han, Wei, Jin, Northern and Southern Dynasties period is 0.5970, which is less than 0.64, indicating a random spatial distribution of cultural heritage sites during this period.The CV values for the Prehistoric and  Pre-Qin period, Sui, Tang, and Five Dynasties period, Song and Yuan period, Ming and Qing period, and Modern era are 1.1084, 0.8992, 0.9559, 0.9734, and 0.8789 respectively, all exceeding 0.64, indicating an aggregated spatial distribution of cultural heritage sites during these five periods.

The evolution of spatial forms
This study employed the Standard Deviational Ellipse method to calculate the spatial morphological evolution characteristics of cultural heritage sites in the northern Fujian region during six historical periods, as presented in Table 2.The results were visualized using ArcGIS, depicted in Fig. 4.
During the Prehistoric and Pre-Qin period, the standard deviation ellipse exhibits a northeast-southwest orientation.In the Qin, Han, Wei, Jin, Northern and Southern Dynasties period, the standard deviation ellipse also shows a northeast-southwest orientation, with the ellipse becoming more flattened, and its center moving northwestward compared to the previous historical period.During the Sui, Tang, and Five Dynasties period, the standard deviation ellipse displays a northwestsoutheast orientation, tending towards a circular shape, and its center shifting southeastward compared to the  previous historical period.In the Song and Yuan period, the standard deviation ellipse presents a northeastsouthwest orientation, with the ellipse becoming nearly circular, and its center moving southwestward compared to the previous historical period.In the Ming and Qing period, the ellipse slightly exhibits a northeast-southwest orientation, becoming more circular in shape, and its center moving southwestward compared to the previous historical period.In the Modern era, the standard deviation ellipse slightly shows a northeast-southwest orientation, tending towards a circular shape, and its center moving northeastward compared to the previous historical period.

The evolution of spatial densities
This study utilized the Kernel Density Estimation method to calculate the spatial density evolution characteristics of cultural heritage sites in northern Fujian during six historical periods, as illustrated in Fig. 5.
In the Prehistoric and Pre-Qin period, as depicted in P1 of Fig. 5, high kernel density values of cultural heritage sites clustered mainly in Songxi and Wuyishan.The secondary high kernel density values were concentrated in Pucheng.Additionally, there were sporadic cultural heritage sites in Shunchang, Guangze, Shaowu, and Pucheng.During this period, the spatial distribution of cultural heritage sites showed a small part of agglomeration and a large part of dispersion.During this period, such distribution patterns are primarily attributed to the fact that the Songxi, Wuyishan, and Pucheng areas were important regions for population aggregation and activities, thus leaving behind a considerable amount of cultural heritage, much of which dates back to the Shang and Zhou dynasties.In fact, as early as the Bronze Age, Wuyishan served as a focal point for the ancestors of the Minyue people, with significant cultural relics such as the Wuyishan cliff tombs and Zhulinkeng kiln sites still preserved to this day.
In the Qin, Han, Wei, Jin, Northern and Southern Dynasties period, as shown in P2 of Fig. 5, high kernel density values of cultural heritage sites clustered mainly in Pucheng.Additionally, there were a few scattered cultural heritage sites in Wuyishan, Shaowu, Songxi, and Shunchang.During this period, there are fewer cultural heritage remains, exhibiting a dispersed spatial distribution, which significantly differs from the aggregated distribution seen in other periods.The primary reason for this disparity may be closely related to the relatively low population in northern Fujian during this time.The decrease in population in northern Fujian during this  Songxi, while sporadic cultural heritage sites were present in Shaowu, Jian'ou, and the border areas of Yanping and Shunchang.During this period, the spatial distribution of cultural heritage sites exhibited a diffusion pattern in a "mesh-filling" manner, forming a "multi-core grouptype belt-shaped structure".Due to the relatively recent historical period, each region has left behind abundant cultural heritage sites, predominantly comprising temples, ancestral halls, pagodas, and bridges.
In the Modern era, as shown in P6 of Fig. 5, high kernel density values of cultural heritage sites were relatively dispersed, primarily distributed in the western parts of Wuyishan, Pucheng, Guangze, Zhenghe, and the border area of Shunchang and Yanping.The secondary high kernel density values clustered mainly in Wuyishan, the border area of Wuyishan and Pucheng, the southern part of Zhenghe, and the border area of Jian'ou and Yanping.During this period, cultural heritage sites exhibited a partially belt-shaped distribution on a small scale, with the overall pattern still characterized by a "core-edge" distribution.During this period, the types of cultural heritage sites are primarily associated with the revolutionary red culture.The spatial distribution of cultural heritage sites during this period is less influenced by the distribution of human settlements and is more influenced by the revolutionary activities and locations of wartime outbreaks led by the Communist Party of China.

Relationship between distribution of cultural heritage sites and elevation
Based on the topographical conditions of northern Fujian, elevations are divided into five levels as shown in Fig. 6.Overlaying the cultural heritage sites with elevation data reveals that the majority of cultural heritage sites in the northern Fujian region are distributed within an elevation range below 400 m.
In Fig. 6, at P1, during the Prehistoric and Pre-Qin period, there are 37 cultural heritage sites, all located in the low hills below 400 m in elevation.Among them, 9 are below 200 m, and 28 are between 200 and 400 m in elevation.This distribution may be related to the fact that human activities at that time mainly relied on natural resources and the ecological environment.The low mountainous areas had relatively gentle terrain, abundant water sources, and fertile land, making them suitable for early human farming and settlement activities.
In Fig. 6, at P2, during the Qin, Han, Wei, Jin, Northern and Southern Dynasties period, the number of cultural heritage sites sharply decreases compared to the previous period, with only 9 sites.Among them, 2 Fig. 6 The relationship between distribution characteristics of cultural heritage sites and elevation in each historical period are below 200 m, 5 are between 200 and 400 m, and 2 are between 400 and 600 m in elevation.This change may be related to historical turmoil, social instability, and population migration.Despite the decrease in the number of sites, they were still predominantly located in low-altitude areas, possibly because these areas remained relatively stable for living and farming activities.
In Fig. 6, at P3, during the Sui, Tang, and Five Dynasties period, there is a significant increase in the number of cultural heritage sites compared to the Qin, Han, Wei, Jin, Northern and Southern Dynasties period, rising to 43 sites.Cultural heritage sites are mainly concentrated in low hills and river valleys.Among them, 11 sites are below 200 m, 19 are between 200 and 400 m, 7 are between 400 and 800 m, and 6 sites are above 800 m in elevation.With social stability and economic development during this period, the population increased, leading to a growing demand for residential and farming land.River valleys, due to their fertile land and convenient water conditions, became important areas for human activities.
In Fig. 6, at P4, during the Song and Yuan period, there is a further increase in the number of cultural heritage sites, totaling 126.From the distribution of cultural heritage sites by elevation, similar to the Sui, Tang, and Five Dynasties period, they are mainly distributed at low elevations, but there is a more pronounced trend of cultural heritage sites extending to higher elevations.During this period, there are 45 sites below 200 m, 47 between 200 and 400 m, 22 between 400 and 800 m, and 12 sites above 800 m in elevation.This change may be related to the economic prosperity and population growth at that time.Additionally, with advancements in agricultural technology and improved water facilities, human activities gradually expanded to higher altitude areas.Furthermore, cultural exchanges and trade activities during the Song and Yuan period may have also promoted the distribution of cultural heritage sites in higher altitude regions.
In Fig. 6, at P5, during the Ming and Qing period, the number of cultural heritage sites experiences a rapid increase, reaching its peak at 365.From the distribution of cultural heritage sites by elevation, there is no significant change compared to the Song and Yuan period, with the majority of sites below 400 m in elevation.During this period, there are 101 sites below 200 m, 180 between 200 and 400 m, 44 between 400 and 600 m, 19 between 600 and 800 m, and 21 sites above 800 m in elevation.This growth may be attributed to the continued development of the socio-economic conditions, population growth, and further advancements in agricultural technology during the Ming and Qing period.Additionally, the political stability and cultural prosperity during this time provided favorable conditions for the protection and inheritance of cultural heritage sites.
In Fig. 6, at P6, during the Modern era, there is a slight decrease in the number of cultural heritage sites, with only 98 sites.From the distribution of cultural heritage sites by elevation, although the majority are still below 400 m, unlike before, many sites are now distributed at elevations above 600 m.During this period, there are 27 sites below 200 m, 39 between 200 and 400 m, 14 between 400 and 600 m, 9 between 600 and 800 m, and 9 sites above 800 m in elevation.The number of sites at higher altitudes relatively increased during this period, which may be related to the significant red revolution struggles in the northern Fujian.This is because the red revolution activities and battlefields often occurred in mountainous areas and rural regions.

Relationship between the distribution of cultural heritage sites and major river systems
Through the establishment of two buffer zones, 0-3 km and 3-6 km, along the main rivers in northern Fujian, the relationship between the distribution of cultural heritage sites and these buffer zones was assessed.As shown in Fig. 7, site P1, among a total of 37 cultural heritage sites from the Prehistoric and Pre-Qin periods, 11 are located within 0-3 km of the river, while 5 are within 3-6 km.Similarly, site P2, from the Qin, Han, Wei, Jin, Northern, and Southern Dynasties period, has 3 sites within 0-3 km of the river, with the remainder located beyond 6 km.Site P3, representing the Sui, Tang, and Five Dynasties period, includes 16 sites within 0-3 km and 4 within 3-6 km of the river out of a total of 43 sites.Site P4, from the Song and Yuan periods, contains 38 sites within 0-3 km and 22 within 3-6 km out of 126 sites.Furthermore, site P5, encompassing the Ming and Qing periods, includes 104 sites within 0-3 km and 52 within 3-6 km out of 365 total sites.Lastly, site P6, from the Modern era, comprises 35 sites within 0-3 km and 13 within 3-6 km out of a total of 98 sites.Overall, there is a close relationship between the distribution of cultural heritage sites and the main rivers.This is primarily due to the mountainous terrain of northern Fujian, where only the areas along the main rivers offer relatively flat open spaces, leading to the majority of human settlements being established along rivers.The rivers not only provide essential water sources for the local population but also serve as crucial support for ancient agricultural irrigation and human livelihoods.Additionally, ancient waterways served as crucial transportation routes, further reinforcing the tendency for settlement along waterways.

The relationship between distribution characteristics of cultural heritage sites and cultural environment Main social cultures in northern Fujian
The overall layout of cultural heritage sites is significantly shaped by the natural geographical environment, while subsequent socio-cultural environments refine and solidify this evolutionary process [41].The Min culture, as a regional culture within the diversified Chinese cultural system, and the northern Fujian culture, as a secondary regional culture within the broader Min culture, exemplify this progression.The northern Fujian culture embodies the common traits of Chinese and Min cultures, centered around Han culture while assimilating elements from southern ethnic minority cultures.In its distinctive geographical setting, it developed into a regionally distinctive culture [42].
Broadly speaking, the northern Fujian culture encompasses not only ancient cultural facets but also those emerging in the Modern era.Its essence encompasses prehistoric stone culture, Minyue culture, religious beliefs and customs culture, Zhu Xi's Neo-Confucianism culture, tea and porcelain ancient road culture, bookstore inscription culture, academy culture, and the culture of the recent red revolutionary movements, among others.Under the dual influence of natural environmental shaping and socio-political-economic development across different periods, unique and influential cultures of the time emerged, significantly impacting the distribution of cultural heritage sites.However, the distribution of cultural heritage sites in each period is still influenced by the continuity of past cultures.Notably, Minyue culture, tea and porcelain ancient road culture, Zhu Xi's Neo-Confucianism culture, religious beliefs and customs culture, and red revolutionary culture have had a significant impact on the spatial distribution characteristics of cultural heritage sites across historical periods, as depicted in Table 3.

Distribution of cultural heritage sites and major social cultures
Based on the selection of cultural heritage sites corresponding to the five social cultures, we utilized spatial visualization mapping techniques to provide a more intuitive representation of their spatial distribution characteristics (Fig. 8).Building upon this, the following sections will provide a more detailed explanation of the implications of the content of the five social cultures and their influence on the distribution of cultural heritage sites. (

1) Minyue culture and cultural heritage sites
The Minyue culture can be divided into the early Minyue culture, dominated by the indigenous Minyue people from prehistoric times to the  The climate in northern Fujian, characterized by "frequent rain in the spring, dense mist and dew, and lingering chill even in midday, " combined with the rich and loose soil, is extremely conducive to the growth of tea leaves.This region boasts an ancient history of tea cultivation and production, fostering a deep-rooted tea culture.Among the significant sites is the national-level cultural heritage site, the Beiyuan Imperial Tea Firing Ruins, which is the historical location of the "Beiyuan Tribute Tea." The tradition of "Beiyuan Tribute Tea" originated in the Tang Dynasty and flourished during the Song Dynasty, enduring as a royal tribute for over 400 years and acclaimed by Emperor Huizong of Song as "the tribute of Jianxi, renowned throughout the realm." Those who partook in this tea culture always possessed specialized tea vessels.The abundant resources of pottery clay facilitated the prosperous development of ancient pottery kilns in northern Fujian.In the cultural heritage sites, the ancient kiln sites in northern Fujian are mostly from the Sui, Tang, and Five Dynasties periods, as well as the Song and Yuan periods.Among them is the famous Jian Kiln, one of the eight great kilns in China, known for its black glazed porcelain.It was once highly esteemed as a tribute and favored by the imperial court.Additionally, the private kiln industry in northern Fujian, aimed at commercial exchange, flourished, especially during the Song and Yuan periods, with numerous kiln sites.The transportation of tea and porcelain relied heavily on the development of transportation routes.Initially, due to "treacherous mountains and forests spanning thousands of miles, " external exchanges for northern Fujian were challenging.However, with increasing exchanges of goods and passengers, during the Sui, Tang, and Five Dynasties periods, postal roads and checkpoints gradually emerged.Official highways leading to the capital were constructed, significantly strengthening the connection between northern Fujian and the central plains, as well as the Zhejiang-Jiangxi region.Consequently, many cultural heritage sites in Wuyishan, Pucheng, and Zhenghe from the Sui, Tang, and Five Dynasties, and the Song and Yuan periods originated from these ancient roads and checkpoints.For instance, the national-level protected cultural heritage site, the Min-Gan Ancient Post Road in Wuyishan, stands as a testament to northern Fujian's crucial trade routes from the Five Dynasties to the Southern Song period.Apart from overland routes, waterways were also vital channels for external exchanges in northern Fujian.Especially significant for pottery production due to its reliance on raw materials, fuel, and transportation, kilns were often established near water routes [44].As the upper reaches of the Minjiang river basin, northern Fujian featured numerous tributaries and a dense network of rivers, constituting the primary historical transportation routes.The ecological environment serves as the material foundation for the derivation of any culture, with different ecological conditions giving rise to diverse cultural manifestations [45].As the birthplace and thriving center of Neo-Confucianism, northern Fujian's unique natural environment played a distinct role in promoting the dissemination and development of Neo-Confucianism.The rich ecological environment, characterized by lush forests and bamboo groves covering the hills and valleys, provided abundant high-quality raw materials for the flourishing woodblock printing industry.The abundant resources of bamboo, essential for woodblock carving, and the availability of quality paper locally contributed to the extensive production of "Jianben" books in this region.Zhu Xi praised Jianyang as the "treasury of books, " and he commended its books as reaching "every corner of the land.

Discussion
Cultural heritage sites serve as carriers that to some extent reflect the mutual constraints, connections, and interactions between human society and the natural environment.The natural environment constitutes the macro-material foundation for the layout of cultural heritage sites, while intrinsic social and cultural influences play a role in reshaping them.The distribution and changes of these sites can reflect the human-environment relationship during specific historical periods.This study utilizes GIS spatial analysis techniques to examine the spatial distribution characteristics of cultural heritage sites in northern Fujian, China, from a historical evolution perspective, and their relationship with natural and cultural environments.This research contributes to international cultural heritage studies in the following ways.On one hand, investigating the relationship between the spatial distribution of cultural heritage sites and historical periods is of great significance as it can reveal the characteristics and patterns of human activities during different historical periods.In existing literature, many scholars have conducted in-depth studies on the relationship between the spatial distribution of cultural heritage sites and historical periods, proposing various theoretical viewpoints.The "natural environment impact theory" on the spatial distribution of cultural heritage, which suggests that the historical spatial distribution evolution of cultural heritage sites is mainly due to changes in human civilization's adaptation to the natural environment, is a viewpoint endorsed by many scholars [48][49][50].However, some scholars have pointed out that besides natural factors, factors such as the development of productivity, changes in political regimes, economic development, trade, and transportation are also driving forces behind the generation and migration of cultural heritage sites [51].Therefore, some existing studies have begun to analyze the reasons for the spatial evolution of cultural heritage in different historical periods from a comprehensive perspective of both natural and human factors, aiming to more systematically reflect the production modes, social structures, and cultural characteristics of human society at that time [11,52,53].The exploration and attempt made in this study from both natural and human perspectives also represent a proactive response to the current trend of research, which can provide effective references for comparative studies in other countries or regions.On the other hand, integrating GIS technology to understand the geographic distribution characteristics of cultural heritage sites and their relationships with natural and socio-cultural factors contributes to a deeper understanding of the interaction between humans and the environment.Currently, GIS technology offers powerful spatial analysis tools capable of integrating geographic data of cultural heritage sites with natural elements such as terrain, altitude, rivers, and soil, as well as socio-cultural factors including historical mainstream cultures, population distribution, economic development levels, and transportation networks.This integration allows for a comprehensive analysis of the multifaceted factors influencing the formation and evolution of cultural heritage sites [19,54,55].This study effectively integrates GIS spatial analysis technology into the spatial evolution research of cultural heritage sites in northern Fujian across different historical periods.Such comprehensive analysis provides an interdisciplinary methodological framework for international cultural heritage research, enabling a more comprehensive explanation of the historical evolution and development of cultural heritage sites.Moreover, it offers scientific basis and decision-making support for the protection and revitalization of similar cultural heritage sites.
The findings of this study also have practical implications for policymakers and cultural heritage managers in the scientific protection, inheritance, and utilization of cultural heritage resources in northern Fujian.First, using the spatial distribution characteristics of different historical periods to guide conservation priorities, policymakers can prioritize cultural heritage conservation based on the spatial distribution differences of cultural heritage sites across different historical periods.For example, for cultural heritage sites from the Ming and Qing periods, efforts can be intensified to ensure their integrity and sustainable development, while for fewer sites from the Qin, Han, Wei, Jin, and Northern and Southern Dynasties periods, conservation efforts can be enhanced through resource integration to prevent further damage.Second, utilizing the influence of terrain and river distance to guide cultural heritage planning and development, policymakers and heritage managers can integrate these influencing factors into rational planning and development strategies.For instance, in areas closer to rivers, cultural tourism resources related to rivers can be developed to enhance the attractiveness of tourist destinations, while in areas farther from rivers, preserving the natural environment can be considered to promote the combination of ecological tourism and cultural heritage conservation.Third, leveraging the micro-shaping role of socio-cultural factors to guide the inheritance and utilization of cultural heritage, policymakers should focus on understanding and protecting these factors.For example, for cultural heritage sites influenced by Minyue culture, tea and porcelain ancient road culture, Zhu Xi's Neo-Confucianism culture, religious beliefs and customs culture, red revolutionary culture, etc., efforts can be made through thematic exhibitions, cultural activities, and other means to strengthen the inheritance and promotion of their historical significance and cultural value.
Although this study has delved into the spatiotemporal evolution characteristics of cultural heritage sites in northern Fujian, China, and their relationship with the natural and cultural environment, there are still some limitations that need to be addressed in future research.First, although this study explored the relationship between cultural heritage sites and the natural environment, research on the micro-level influence of sociocultural factors on the spatial distribution of cultural heritage sites is still limited.By introducing more analytical techniques, future research can delve deeper into the distribution patterns of cultural heritage sites under different historical socio-cultural backgrounds, providing a more comprehensive understanding of the formation and evolution of cultural heritage sites.Second, this study relies on the lists of cultural relics protection units at all levels as the source of cultural heritage site data.Although this data source can accurately reflect the distribution of cultural heritage sites in the northern Fujian to the greatest extent, it is acknowledged that this approach may still overlook some sites with historical, cultural, or scientific value that have not been officially designated as protected units, thereby affecting the accurate description of the overall spatiotemporal characteristics.In future research, it may be beneficial to consider integrating other data sources (such as historical documents, archaeological excavation reports, field surveys) and including other cultural heritage sites not listed in the protection units registry to deepen the comprehensive understanding of the relationship between cultural heritage sites in northern Fujian and their natural and cultural environments.Third, the river data used in this study consist of five levels of river data.While these five levels of river data can largely reflect the natural scale of rivers and their significant impact on social and economic development, it is important to acknowledge that there may be some more nuanced tributary river data outside these five levels whose influence on cultural heritage sites has been overlooked.In the future, integrating more detailed river data, while ensuring the reliability of the data sources, may enhance the understanding of the relationship between rivers and the distribution of cultural heritage sites.

Conclusion
This study employed GIS technology to analyze the spatiotemporal evolution characteristics of cultural heritage sites in northern Fujian, China, across different historical periods, and explored the relationship between the distribution characteristics of cultural heritage sites and the natural environment, as well as local socio-cultural factors.The main conclusions are as follows: (1) Cultural heritage sites in northern Fujian exhibit differences in spatial distribution across each historical period.The Ming and Qing periods have the highest number of cultural heritage sites, which are also the most concentrated.Conversely, the Qin, Han, Wei, Jin, Northern, and Southern Dynasties periods have the fewest cultural heritage sites, which are more dispersed.(2) Regarding the topography, altitude, and distance from rivers of cultural heritage sites in each historical period, there is a close relationship with contemporary production and life.These sites are mainly located in regions with favorable natural resource conditions conducive to human production and life, such as mid to low altitudes, relatively flat mountain basins, river valleys, and low hills.Additionally, localized abrupt changes in history cannot be ruled out, such as the prevalence of red revolutionary sites in the Modern era, which were distributed in high-altitude mountainous areas not most suitable for production and life due to the specific social environment at that time.
(3) The overall layout of cultural heritage sites in northern Fujian tends to be influenced not only by macro constraints from the natural environment but also by micro-shaping from mainstream socio-cultural factors in each historical period.Notably, five categories-Minyue culture, tea and porcelain ancient road culture, Zhu Xi's Neo-Confucianism culture, religious beliefs and customs culture, and red revolutionary culture-have had significant impacts on the spatial distribution of cultural heritage sites across different historical periods.

( 1 )
Reveal the spatial distribution characteristics of cultural heritage sites in the northern Fujian during different historical periods.(2) Analyze the correlation between the distribution characteristics of cultural heritage sites in the northern Fujian during different historical periods and the natural environment.(3) Explore the influence of the main social cultures in the northern Fujian during different historical periods on the formation and distribution of cultural heritage sites.

Fig. 3
Fig. 3 The Vornoni diagrams of each historical period in northern Fujian (P1 represents the Prehistoric and Pre-Qin period.P2 represents the Qin, Han, Wei, Jin, Northern and Southern Dynasties period.P3 represents the Sui, Tang, and Five Dynasties period.P4 represents the Song and Yuan period.P5 represents the Ming and Qing period.P6 represents the Modern era.The historical period representation in Figs. 4, 5, 6 and 7 is the same as in this figure.)

Fig. 4
Fig. 4 Standard deviational ellipse and mean center for each historical period

Fig. 5
Fig. 5 Kernel density distribution of cultural heritage sites in each historical period

Fig. 7
Fig. 7 Distribution of cultural heritage sites near the river in each historical period

Table 1
Nearest neighbor index of spatial distribution of cultural heritage sites in historical periods

Table 2
The calculation results of standard deviational ellipse and mean center for each historical period

Table 3
Main social cultures affecting the distribution of cultural heritage sites in each historical period The relationship between distribution characteristics of cultural heritage sites and cultural environmentWuyi suspended coffins in Wuyishan, the Hongqiao board and the Ma'er Mountain site in Pucheng, and the Pucheng earthen mound tombs, all of which are national-level cultural relics protection units.

Zhu Xi's neo-confucianism culture and cultural heritage sites
The convenient water routes closely linked northern Fujian to Fuzhou in history.A continuous flow of goods from northern Fujian sailed down the Minjiang river to Fuzhou, eventually reaching the sea.This economic and trade development drove a period of cultural prosperity.(3) The founder of Zhu Xi's Neo-Confucianism culture, Zhu Xi, lived for 71 years, spending over 60 years in northern Fujian.During this time, he and his disciples established academies, engaged in exchanges of academic and cultural ideas, and initiated activities for creation and dissemination.As a result, Zhu Xi left numerous tangible cultural remnants in northern Fujian.Various cultural relics related to Zhu Xi's upbringing, education, lectures, and writings are still preserved across northern Fujian.Notable examples include the Yungen Academy and Xingxi Academy in Zhenghe, the Hanquan Retreat, Yungu Cottage, and Kaoting Academy in Jianyang, the Zhu Zi Temple and Boshi Mansion in Jian'ou, the Wufu Town and Wuyi Retreat in Wuyishan, among others.These sites constitute valuable resources for Zhu Xi's Neo-Confucianism culture in northern Fujian.