1. Introduction
Vernacular dwellings constitute a vital category of traditional architecture steeped in profound historical and cultural significance. Their construction embodies the values of harmonious coexistence between humans and their environment, as well as the synergy between regional characteristics and architectural design. China has a vast territory, a long history, and a large number of ethnic groups. Different geographical environments, cultural backgrounds, and economic conditions have given birth to a variety of vernacular dwellings. On one hand, Chinese vernacular dwellings distinctly reflect regional disparities influenced by natural factors such as topography, climate, and available building materials. Consequently, we observe a spectrum of residential styles, exemplified by the Siheyuan in the North China Plain [
1], cave dwellings in the Loess Plateau [
2], and Tulou in the western Fujian Mountain area [
3]. On the other hand, Chinese vernacular dwellings are intricately intertwined with the socio-cultural milieu, encompassing factors such as the distribution of ethnic groups, social organizations, and cultural traditions. This interplay bestows upon them a profusion of ethnic characteristics, exemplified by the Diaolou of the Tibetan ethnicity [
4], bamboo houses of the Dai ethnicity [
5], and yurts of the Mongolian ethnicity [
6]. Indeed, within the dynamic framework of regional and humanistic environments, socio-economic considerations, and other factors at play, some vernacular dwellings in China elude precise categorization. They have both “common” characteristics and “differentiation” characteristics such as mixing, adaptation, and integration. This phenomenon often occurs in natural geographical transition areas and cultural fringe areas. As one of the important residential types in China, Tibetan residences have garnered global recognition for their unassuming architectural designs, colorful architectural decoration, and profound religious ambiance. In recent years, Tibetan studies have expanded beyond the central Tibetan areas to encompass the peripheral realms of Amdo and Kham [
7]. This evolution in research paradigms has shifted from the pursuit of commonalities to the exploration of complexity, diversity, locality, and pluralism. This transformation aptly mirrors the essence of Tibetan culture’s pluralistic integration. Hence, Tibetan vernacular dwellings possess a dual nature—rooted in shared origins yet marked by significant differentiation.
The Gannan Tibetan Autonomous Prefecture, known as the “gateway to the Qinghai-Tibet Plateau”, occupies a unique geographical position at the crossroads of the Qinghai-Tibet Plateau and Loess Plateau. Its topography is marked by complexity and diversity, with higher elevations in the northwest gradually giving way to lower terrain in the southeast, resulting in a transition in natural conditions. Gannan is also a transitional zone between agricultural and pastoral regions, with agriculture and animal husbandry serving as its primary economic cornerstones [
8]. Additionally, Gannan represents a convergence of Tibetan and Han cultures, which is the Tibetan border area. This Tibetan border area can be categorized into two levels: one encompasses Tibetan regions beyond the Tibet Autonomous Region, including the four provinces of Gansu, Qinghai, Sichuan, and Yunnan, while the other includes the northeastern and southeastern fringes of the Tibetan Plateau. Cultural differentiation often manifests prominently in border areas due to the gradual attenuation of cultural characteristics with increasing distances of transmission. These cultural border regions are particularly susceptible to the influences of neighboring cultures, leading to a dynamic interplay and mutual enrichment among two or more cultures, ultimately fostering compatibility and symbiosis [
9]. Within this intricate backdrop, Gannan has borne witness to the emergence of distinctive Tibetan vernacular dwellings, particularly in its semi-agricultural and semi-pastoral regions—a quintessential district exemplifying cultural compatibility. These Tibetan dwellings have undergone isomerism, evolving, developing, and varying over time. They bear witness to the harmonious coexistence between humanity and the natural environment, encapsulating the historical and cultural transformations within Gannan Prefecture.
In the 17 Sustainable Development Goals (SDGs) proposed by the United Nations in 2015, SDG11 aimed for inclusive, safe, resilient, and sustainable cities. In terms of human settlements, its specific targets emphasized the preservation of cultural heritage and positive social links between urban, peri-urban, and rural areas [
10]. The configuration of vernacular dwellings conveys culture because it follows the layout and form of the dwellings and can be considered the materialized expression of regional culture [
11]. As part of the cultural heritage, the preservation of tangible and intangible values of vernacular dwellings is crucial to achieving the goals of sustainable development.
In early 2003, the Central Committee of the Communist Party of China (CPC) introduced a rural construction strategy, marking the inception of efforts towards rural revitalization. The formal proposal for rural revitalization was enshrined in the report of the 19th National Congress. Subsequently, the 20th National Congress report underscored the comprehensive advancement of rural revitalization, emphasizing the need for the robust development of rural industries, talents, culture, ecology, and organizations [
12]. In this context, vernacular dwellings assume a pivotal role in facilitating sustainable development in rural areas. As L.Y. Wu expressed, “Our objective is to create a sustainable and delightful living environment. To achieve this, we must harness the inherent richness of architectural culture across different regions, uphold traditions, incorporate innovation, and construct living spaces imbued with health, positivity, and profound cultural significance” [
13]. Balancing material production and regional cultural inheritance amid rapid urbanization and continuing the diverse daily lifestyle of rural residents have become urgent issues.
The examination of peripheral areas serves as more than just an extension of our comprehension of regional dwellings; it also signifies a renewed recognition and contemplation of domains that have long been overlooked or disregarded. Such investigations are instrumental in preserving cultural diversity and fostering the sustainable development of vernacular dwellings. To deeply explore the spatial configuration of the Tibetan dwellings in Gannan’s semi-agricultural and semi-pastoral areas, this study posits three fundamental questions: (1) How to identify an effective tool for unveiling the isomerism phenomenon in residential buildings? (2) What is the corresponding sociocultural connotation behind the isomerism phenomenon of residential configuration? (3) How can residential buildings attain sustainable development? This study employs space syntax as the research methodology, acquires firsthand data via field research and mapping, quantifies the spatial attributes of Tibetan dwellings in Gannan’s semi-agricultural and semi-pastoral regions through numerical analysis, and constructs mathematical models to extract spatial and cultural insights from these dwellings. As a result, it unveils the sociocultural rationale that underpins their physical structure.
5. Discussion
5.1. Discussion of Research Methodology
This study conducts a quantitative analysis of the spatial configuration of residential buildings using space syntax methodology, thus revealing the latent logic governing spatial structure and social organization within architectural spatial units. Spatial structure typically manifests in the form of points, lines, and planes, and a single syntactic analysis method may not comprehensively identify all three forms. To address this limitation, the Depthmap software is employed to perform JPG and VGA analyses, offering insights into the spatial configuration of residential dwellings from both feasible and visible perspectives. The JPG analysis method is applied to examine node types, structural characteristics, and calculations of variable indexes concerning residential buildings. These analyses uncover residents’ behavioral trajectories within residential spaces, establishing connections with the unique sociocultural factors in Gannan. This comprehensive analysis complements our understanding of the overall spatial configuration of residential buildings through VGA diagrams. For instance, consider the residence in the Niba village, Zhuoni County (ZN-NB1), where both the corridor and the main room possess identical integration values, signifying their central importance. However, the VGA diagram reveals a heightened level of interaction within the main room, a phenomenon further elucidated by psycho-emotional behaviors, historical context, and cultural influences. The combined utilization of these two analytical methods allows for an exploration of lifestyle, behavioral patterns, psychological states, and cultural underpinnings based on the spatial configuration of residential buildings. This approach unveils the role of sociocultural order behind isomerism and introduces a novel perspective for the in-depth examination of the spatial morphology of residential buildings.
5.2. Tracing the Origin of the Isomerism of Residential Buildings
5.2.1. The Historical Evolution of Residential Buildings
Under the influence of different historical opportunities, the spatial configuration of Tibetan dwellings in different counties witnessed differences. The structure of the JPGs of the Tibetan dwellings in Zhuoni County is simple, especially in the Niba Village. Inside the dwellings, the space for Buddhist rituals is shared with the living space. Since the settlement of the Niba ancestors, they have been deeply influenced by the culture of central Tibet, and the spatial layout of this undifferentiated dwelling has inherited the spatial organization logic of the tents used in nomadic life (
Figure 9), which shows prototypical characteristics. The structure of the JPGs of the Tibetan dwellings in Xiahe County is relatively complex, with compact spaces and independent space functions. This spatial configuration is closely related to the Labrang Monastery built in Xiahe County during the Kangxi period of the Qing Dynasty [
54]. Since its construction, the religious influence of the Labrang Monastery has been growing, and it has become an important node on the Ancient Tea-Horse Road, attracting many Han merchants and Hui merchants to settle and trade here. With the infiltration of Han and Hui residential culture, the spatial configuration of Tibetan residential houses in Xiahe County absorbed favorable parts based on the prototype of Tibetan residential dwellings, resulting in transitional characteristics. The structure of the JPGs of the Tibetan dwellings in Lintan County is the most complex, and the layout of dwellings has strong symmetry. It is closely related to the historical development of Lintan County. Lintan County was known as “Taozhou” in ancient times. At the beginning of the Ming Dynasty, Jianghuai soldiers stationed in Taozhou defended the city and cultivated the land [
55], which formed and laid the foundation of the Jianghuai culture in Taozhou. The form of dwellings in the Jianghuai area is influenced by the Confucian rituals. The interior of the dwelling is orderly, with a clear central axis and emphasis on primary and secondary (
Figure 10a). The Tibetan dwellings in Lintan County were deeply influenced by the Han culture of the Jianghuai area. The sutra hall is located on the central axis of the building, and the other spaces are lined up around the sutra hall (
Figure 10b), which shows mutant characteristics (
Figure 10b).
5.2.2. The Sociocultural Connotation Continuity of Residential Buildings
The Gannan Tibetan Autonomous Prefecture is located in the transition area between the two strong cultures of Tibet and Han. The kernel of the isomerism of Tibetan residential space lies in the long-term contact, conflict, and integration of the Tibetan culture and Han culture. In Zhuoni County and Lintan County, the potential differences in the cultural intensity between the Tibetan culture and Han culture are obvious. When a certain cultural intensity feature is obvious in the residential space, it plays a dominant role in the spatial configuration. The spatial form of the Tibetan dwellings in Zhuoni County is simple and pure, with no distinction between eating and sleeping, which is more similar to the spatial form of the tents used by Tibetan nomads in central Tibet. The spatial form of the Tibetan dwellings in Lintan County is complex, and the central axis is clear, which is similar to the spatial form of the Han courtyard dwellings in the Jianghuai area. In Xiahe County, in the process of cultural dissemination and evolution, the potential cultural intensity differences between the Tibetan culture and Han culture are relatively small, with comparable control over the spatial configuration of dwellings.
It is not difficult to blindly “copy” the tradition in the process of the continuation and development of architectural culture, but this is not the purpose. We should fully consider the relationship between the space utilization mode of the residential buildings in each town and the cultural connotation. The genotypes of the Gannan Tibetan dwellings are different, but under the historical succession, the Tibetan dwellings inherited the division of the dual space of the “sacred and secular” and paid special attention to the sacred space of the sutra hall. Therefore, in the process of protecting and developing the Tibetan dwellings in Gannan, it is necessary to fully respect the cultural beliefs of the ethnic groups in the area and continue with the fundamental elements of the houses that represent their ethnic culture.
The research results not only consider the architectural form and spatial structure, but also illustrate the cultural connotation and cultural essence conveyed by the vernacular residence in the cultural border area and provide a scientific basis for the inheritance and development of the Tibetan dwellings in Gannan according to local conditions.
5.3. Limitations and Further Research
This study has limitations. It only includes three typical semi-agricultural and semi-pastoral counties in the Gannan Tibetan Autonomous Prefecture. In future studies, the research scope can be expanded, for example, to the entire Tibetan border area, aiming to establish a research system that can summarize the relationship between the use of the residential architecture space and the potential difference in the cultural intensity of the border area. This will provide a sufficient reference for exploring the genotypes of residential buildings in the Gannan area and other cultural fringe areas as well as the continuous development of architectural culture.