Sacred landscapes as refugia for heritage trees: evidence from Nanhua Temple, China

Abstract

Sacred natural sites have long been regarded as informal refugia for biodiversity, yet their role in conserving heritage trees that require multi-century persistence remains insufficiently assessed and quantified. This study investigated the diversity, structural characteristics, health condition, and conservation significance of heritage trees in Nanhua Temple, one of the most historically continuous Buddhist monasteries in China. A comprehensive census was conducted by systematically verifying government inventory records, during which species identity, dendrometry characteristics, age structure, and physiological condition were assessed in accordance with national forestry standards. A total of 285 heritage trees representing 13 species were recorded, dominated by Liquidambar formosana (129 individuals, IV = 43.09%), followed by the introduced Camphora officinarum (21.04%), Schima superba (15.14%), and Castanopsis hystrix (12.81%), which together accounted for over 90% of the total importance value. Diameter and age structures exhibited right-skewed distributions, whereas tree height and crown width showed unimodal patterns, indicating a relatively stable population structure with continuous regeneration and old-growth characteristics. The density of heritage trees within the temple far exceeded regional county-level averages in South China. The globally Critically Endangered relict Glyptostrobus pensilis persisted as the oldest cohort (>500 years), represented by three individuals. However, multiple stressors, including invasive vines, incense smoke, termite infestations, and soil compaction, have also been observed. These findings demonstrate that historically continuous Buddhist temple landscapes can serve as important refugia for heritage trees through long-term cultural stewardship and management continuity. While heritage trees in China are already incorporated into the national protection system, the diversity and conservation value of temple-associated heritage trees deserve greater attention in future management and cultural heritage conservation practices, particularly in rapidly urbanizing regions where sacred landscapes continue to preserve important biocultural resources.

Introduction

Urbanization and land-use change are primary drivers of biodiversity loss and ecosystem degradation, particularly across rapidly developing regions (Ekka et al., 2023; Simanti and Hemraj, 2025). In these landscapes, large and old trees, commonly classified as heritage or veteran trees, fulfill a critical function in maintaining biodiversity and preserving ecological memory (Lindenmayer, 2017; Gilhen-Baker et al., 2022). As keystone structural elements, these trees anchor complex assemblages of epiphytes, cavity-nesting birds, and saproxylic beetles that rely on the specialized microhabitats found in senescent individuals (Lindenmayer and Laurance, 2017; Zapponi et al., 2017). Despite their profound ecological and cultural value, heritage trees are increasingly threatened by urban expansion and a widespread lack of targeted conservation measures (Jim, 2017; Xie et al., 2026).

In recent years, growing attention has been directed toward small-scale landscape enclaves that function as biodiversity refugia in human-dominated environments (Huang et al., 2023; Huang et al., 2025). Among these, sacred natural-cum-cultural sites comprising temple forests, shrine groves, and church woodlands have emerged as critical but underappreciated conservation units (Frascaroli et al., 2016; Ormsby, 2021). These sites are often nurtured and protected through long-standing cultural and religious practices, including taboos against tree cutting or land disturbance, and veneration as deified objects, which inadvertently support the persistence of native vegetation and large trees (Klepeis et al., 2016; Chanu et al., 2025). Consequently, sacred landscapes have been increasingly recognized as'micro-refugia', offering often pertinent and rare biodiversity buffers against anthropogenic pressures (Löki et al., 2019; Gentili et al., 2024). Despite their informal nature, such sites may achieve conservation efficacy comparable to that of formally designated protected areas, particularly for long-lived taxa such as trees (Frascaroli et al., 2016; Plieninger et al., 2023).

Empirical studies across diverse geographical contexts have demonstrated that sacred sites harbor high levels of species richness and structural complexity. Such precious natural pockets may represent vestigial fragments of previously more extensive regional ecosystems. For instance, urban sacred spaces in India exhibit greater tree diversity and abundance than surrounding built environments (Jaganmohan et al., 2018). Shrine forests in Japan and church forests in Ethiopia preserve remnants of original vegetation and support large-diameter trees rarely found elsewhere in cultural landscapes (Ishii et al., 2010; Moore and Atherton, 2021). In Europe, sacred sites and cemeteries have been shown to function as biodiversity hotspots and refugia for both flora and fauna (Frascaroli et al., 2016; Kowarik et al., 2016; Löki et al., 2019). Sacred groves in sub-Saharan Africa and South Asia further demonstrate the global relevance of such sites as complementary conservation systems (Bhagwat and Rutte, 2006; Imarhiagbe and Ogwu, 2022). More recently, research has begun to quantify the structural and functional roles of trees within sacred landscapes. The studies have highlighted their capacity to maintain old-growth attributes, characterized by large crown dimensions, high basal area, complex trunk scaffold and intricate branching habit that have otherwise vanished from intensively managed surroundings (Rath et al., 2020; Marini Govigli et al., 2024).

However, this growing body of research is primarily focused on species diversity, community composition, or ecosystem services, with relatively little attention to the role of sacred landscapes in conserving heritage trees as individual biological and cultural entities (Xie et al., 2026). Heritage trees represent not only key structural components of ecosystems but also living monuments that embody historical continuity, socio-cultural values and collective community memory (Blicharska and Mikusiński, 2014; Lindenmayer and Laurance, 2017; Xie et al., 2026). Understanding their distribution, structural characteristics, and conservation status within sacred sites remains a critical knowledge gap. This shortfall is particularly evident in rapidly urbanizing regions of Asia, where development pressure on peri-urban green spaces has intensified markedly in recent decades (Melaku et al., 2023; Xie et al., 2025b).

The deep‑rooted Buddhist and Taoist traditions of China create a singularly valuable framework for investigating heritage trees from a socio-cultural perspective. Buddhist temples are often associated with ancient trees that have been protected for centuries due to spiritual beliefs, institutional rules, and deep-rooted cultural practices (Nicolaisen, 2019; Huang et al., 2025). These sites may therefore serve as important refugia for heritage trees within increasingly fragmented and nature-deprived urban and peri-urban landscapes. However, systematic empirical evidence quantifying this role in terms of tree density and structural attributes, and comparing it with broader regional baselines, remains limited.

To address this gap, the present study investigates the diversity and structural characteristics of heritage trees in Nanhua Temple, a historically and religiously significant Buddhist site in southern China. Specifically, this study aims to: (1) quantify species composition and abundance of heritage trees; (2) analyze their structural attributes, including diameter at breast height (DBH), tree height, and crown size; (3) assess tree health status and identify key threats; and (4) evaluate the role of this sacred landscape as a refugium for heritage trees by comparing heritage tree density against regional benchmarks. By providing empirical evidence from a representative case study, this research contributes to a broader understanding of the conservation value of sacred landscapes. It highlights their potential integration into formal biodiversity conservation strategies.

Methods

Study site

Nanhua Temple is located approximately 24 km south of Shaoguan City (24°47′N, 113°35′E), Guangdong Province, in the northern part of the Pearl River Delta region, southern China. It is one of the most historically important Buddhist monasteries in China, originally founded in 502 CE during the Liang Dynasty. The venue is closely associated with the Sixth Patriarch Huineng of Chan (Zen) Buddhism (Li et al., 2004). The temple complex covers approximately 0.43 km² and is situated within a valley surrounded by hills, adjacent to the Cao River (Caoxi). The region has a humid subtropical monsoon climate, with a mean annual temperature of approximately 20 °C and a mean annual precipitation of about 1,800 mm, concentrated from April to September (Yang et al., 2020). The surrounding landscape is dominated by subtropical evergreen broadleaf forest, characteristic of the Nanling Floristic Region. The temple grounds support a diverse assemblage of trees maintained within the cultural landscape of the monastic precinct, the enclosed courtyards, and the surrounding woodland buffer zones. The enduring history of continuous religious-institutional management, underpinned by strict prohibitions against tree felling and land disturbance, has ensured effective de facto protection of the tree community for over 15 centuries (Xie and Jim, 2026).

Field survey

A comprehensive census of heritage trees in the grounds of the Nanhua Temple was conducted from 2021 to 2026 (Figure 1), beginning with a baseline inventory retrieved from the Guangdong Heritage Tree Information Management System and followed by rigorous ground-truthing. Heritage trees were identified and categorized by age according to the Forestry Industry Standard of the People's Republic of China (LY/T 2737—2016) into Class I (>500 years), Class II (300–499 years), and Class III (100–299 years) (China Society of Forestry, 2017). To prioritize non-destructive conservation, tree-age data were sourced from official government records rather than invasive wood-core sampling. Species identity was determined in the field through vegetative and reproductive characters (leaf morphology, bark texture, and, where present, flowers or fruits), following the Flora of China and cross-verified against the Plants of the World Online (POWO) database maintained by the Royal Botanic Gardens, Kew, to confirm currently accepted names and authorship. Given that all recorded individuals are legally protected heritage trees, several of which are designated as First- or Second-Class specimens under national heritage-tree regulations, no voucher specimens were collected. Instead, identification relied on non-destructive field observation supplemented by high-resolution photographic documentation of diagnostic characters, cross-checked against the aforementioned taxonomic references. Dendrometry parameters, including diameter at breast height (DBH, measured at 1.3 m), total tree height, and crown width (arithmetic mean of two perpendicular diameters), were systematically recorded.

Figure 1

The physiological vigor of each tree was evaluated using a three-grade visual assessment scale: (1) Healthy, representing individuals with vigorous growth, dense foliage, and no significant structural defects; (2) Declining, characterized by reduced terminal growth, sparse or chlorotic foliage, and evident dieback in the upper canopy; and (3) Imperiled, indicating trees with severe crown dieback exceeding 75% or critical structural instability. Furthermore, external stressors, including mechanical damage, pest infestation, and anthropogenic disturbances, were documented and photographed to assess the overall site condition and conservation status of the grove. This standardized approach ensured that the structural diversity and health of the heritage tree community were quantified while minimizing physical impact on these sensitive biological monuments.

Data analysis

The importance value (IV) was used to assess the ecological dominance of heritage tree species within the relatively homogeneous habitat of Nanhua Temple. It is calculated as IV = (RA + RD) / 2, where Relative Abundance (RA) represents the proportion of individuals of a specific species relative to the total population; Relative Dominance (RD) signifies the proportion of the cumulative diameter at breast height (DBH) of a species relative to the total DBH of all heritage trees (Jim and Zhang, 2013). Structural attributes, including DBH, tree height, and crown width, were summarized using descriptive statistics and visualized in frequency distribution histograms to examine size-class distribution. Also, regression analysis was performed to identify scaling relationships and distribution trends among these key parameters. To evaluate the site's conservation significance, heritage tree density (trees km⁻²) was determined and benchmarked against equivalent data from six representative counties in South China retrieved from peer-reviewed literature and regional inventories (Xu et al., 2018; Zhu et al., 2021; Cui et al., 2022; Su et al., 2024; Xie et al., 2024; Xie et al., 2025a). All statistical computations and curve fitting were conducted using PAST 5.3 (Hammer and Harper, 2001) and Microsoft Excel 2021. The resulting data were synthesized to highlight the temple's role as a critical biodiversity refugium.

Results

A total of 285 heritage trees were recorded in Nanhua Temple, comprising 13 species, 12 genera, and 11 families (Table 1). Of these, 3 individuals were classified as Tier 1 (>500 years), 3 as Tier 2 (300–499 years), and 279 as Tier 3 (100–299 years). Liquidambar formosana (Altingiaceae) was the dominant species, with 129 individuals and the highest importance value (IV = 43.09%). The second most important species was Camphora officinarum (Lauraceae; 56 individuals, IV = 21.04%), followed by Schima superba (Theaceae; 44 individuals, IV = 15.14%) and Castanopsis hystrix (Fagaceae; 36 individuals, IV = 12.81%). These four species together accounted for 92.1% of the total IV. The remaining nine species comprised fewer than 10 individuals each, with IV values below 2.5%, including the only Tier 1 representatives, Glyptostrobus pensilis (Cupressaceae), a globally endangered relict species represented by three individuals. Three of the four dominant species (L. formosana, S. superba, and C. hystrix) are native to the subtropical forests of southern China, whereas the second-ranked C. officinarum was introduced and long cultivated in the region. This species composition demonstrates that the temple's tree assemblage is shaped by both persistence of native flora and historical human cultivation.

The age and DBH of heritage trees at Nanhua Temple showed conspicuous right-skewed distributions, indicating a population dominated by younger and smaller individuals (Figures 2a,b). Specifically, approximately 97.9% of trees were classified as Tier 3, with only three individuals each representing Tier 1 and Tier 2. This demographic profile is statistically validated by a power-law function (y = 243.2x^−2.6, R² = 0.99), which characterizes the rapid decline in tree abundance with increasing age (Figure 2a). A parallel trend was observed in the DBH frequency distribution, which follows an exponential decay model (y = 316.37e^−0.78x, R² = 0.95) and manifests as a typical reverse J-shaped curve (Figure 2b). While most individuals were concentrated in the 20–60 cm DBH range, several large-diameter specimens exceeded 100 cm, contributed primarily by C. officinarum and L. formosana. The regression lines indicate a rapid trend of decline in tree count with age and DBH.

Figure 2

In contrast to the age and diameter distributions, tree height and crown width exhibited unimodal distribution patterns, which are best modeled by quadratic polynomial functions. The tree height frequency followed a downward-opening parabolic trend (y = −5.0x² + 49.2x−57.1, R² = 0.76), with most individuals clustered in the 18.5–22.5 m range (Figure 2c). Similarly, the crown width distribution showed a unimodal structure (y = −6.9x² + 61.2x−63.9, R² = 0.55), predominantly centered on the 17 m interval (Figure 2d). These mid-sized structural dominance patterns suggest that while the heritage trees vary in age and diameter, their vertical growth and lateral canopy expansion within the temple’s micro-environment have reached a relatively harmonized and stable state. The scarcity of individuals in the smallest and largest classes of height and crown width further reflects the structural maturity and physical constraints typical of established sacred groves.

The heritage tree density at Nanhua Temple was calculated to be 662.8 trees km⁻², based on 285 trees recorded within a 0.43 km² site area (Table 2). This value was approximately a thousand times higher than the heritage tree densities recorded across six counties in South China, which ranged from 0.1 to 0.2 trees km⁻². Despite Nanhua Temple’s small spatial footprint, it harbors an exceptionally high density of heritage trees in the regional database, underscoring its potential as a readily available refuge for old trees within a predominantly human-dominated landscape matrix.

The health assessment indicated that most heritage trees at Nanhua Temple remain in healthy or declining condition (Figure 3A), suggesting that long-term cultural and institutional management has largely maintained population vigor and vitality. Some 2.81% of the trees are rated as imperiled, indicating they are in a decline spiral. Some notable localized stressors were identified affecting a subset of the inventory. Proliferation of invasive alien vines was entangling and overtopping some crowns, a condition that could compromise photosynthetic capacity and impose additional structural weight on the host trees (Figure 3B). In the inner temple courtyards, chronic exposure to ritual smoke and incense exerted a notable chronic environmental stressor, contributing to the progressive physiological decline of individuals near primary ritual sites (Figure 3C). Structural vulnerabilities were also documented, including large trunk cavities (Figure 3D) and termite infestations (Figure 3E), both of which undermine mechanical integrity and increase susceptibility to wind-induced failure. Additionally, canopy dieback and root-zone soil compaction were recorded in areas with high pedestrian traffic, signaling localized degradation of the growing environment (Figure 3F).

Figure 3

Discussion

Nanhua Temple as an exceptional refugium for heritage trees

The empirical evidence from Nanhua Temple reinforces the conceptualization of sacred natural sites as extraordinarily effective refugia within anthropogenically modified landscapes. The heritage tree density observed at this site exceeds regional county-level averages by several orders of magnitude, a disparity that transcends mere spatial scale effects or sampling artifacts. Instead, this contrast underscores a fundamentally distinct habitat and an enabling management regime that have persisted over centuries. While the role of sacred sites in biodiversity conservation is well-recognized (Bhagwat and Rutte, 2006; Frascaroli et al., 2016; Huang et al., 2025), such a remarkable concentration of ancient trees within a confined enclave provides a rare quantitative benchmark for “micro-refugia” efficiency (Ormsby, 2021; Zhou, 2025). These findings demonstrate that some sacred landscapes can safeguard organisms requiring multi-century survival windows, which are increasingly unattainable in the surrounding matrix of intensively managed or disturbed lands.

The resilience of this refugium is deeply rooted in the synergy between institutional longevity and socio-cultural prohibitions. Unlike many formal nature reserves, which may be vulnerable to shifting political priorities, boundary redefinitions, or lapses in enforcement, Nanhua Temple has maintained a continuous management tradition for over 15 centuries. Buddhist monastic codes, particularly those emphasizing the sanctity of vegetation associated with the legacy of venerated patriarchs, have historically functioned as a robust and enduring form of de facto conservation (Salick et al., 2007; Dudley et al., 2012; Xie and Jim, 2026). This institutional stability ensures a consistent governance framework that buffers heritage trees against the volatility and capriciousness of external land-use changes. Preserving a site over centuries provides the necessary conditions for nurturing and protecting trees. The concomitant long-term observation of tree reverence ethos provides sufficient conditions for delivering the heritage-tree sequels. Our study suggests that the internal consistency and persistence of temple-based taboos provide a unique model of conservation governance (Sinthumule, 2024), where cultural norms translate directly into tangible ecological outcomes, specifically the persistence of a dense and diverse assemblage of old trees.

While local topography and low physical disturbance in mountain valleys undoubtedly provide favorable site conditions for tree growth, abiotic factors alone are insufficient to explain the multi-century persistence of exceptional densities of heritage trees. A clear distinction should be made between general forest stands (e.g., village fengshui groves or secondary natural forests) and the distinct category of heritage trees. Standard forest surveys in fengshui groves or natural woodlands evaluate overall community dynamics across all size classes, including saplings and understory shrubs (Hu et al., 2011). In contrast, heritage trees represent a rare cohort of long-lived biological monuments whose survival requires uncompromised, multi-century protection against logging, land clearing, and drastic human disturbance across dynastic transitions and socio-economic shifts (Xie et al., 2026). Regional empirical evidence indicates that non-sacred woodlands and community fengshui groves, despite their ecological value, remain highly vulnerable to changing village governance, tenure fragmentation, and agricultural encroachment over extended timescales (Chen et al., 2018; Liang et al., 2025). Conversely, historically continuous Buddhist and Taoist temple landscapes systematically exhibit disproportionately high densities and extraordinary temporal persistence of ancient trees across China and Asia (Huang et al., 2025; Jin et al., 2025). For instance, recent regional and national syntheses demonstrate that religious temples serve as persistent macro- and micro-refugia for old trees in human-dominated matrixes by providing institutional longevity that far exceeds typical secular forest management cycles (Huang et al., 2023; Xie and Jim, 2026). Thus, while neighboring non-sacred or fengshui forests maintain general woody biodiversity, the multi-century institutional protection unique to millennial Buddhist sites like Nanhua Temple acts as the decisive filter enabling trees to reach and maintain heritage status.

Furthermore, the high density and close spacing of heritage trees foster enhanced ecological connectivity and structural complexity within the temple grounds. These important trees serve as biological anchors, maintaining a diverse range of specialized microhabitats that support rare epiphytic and saproxylic communities (Sillett and Pelt, 2007; Lindenmayer and Laurance, 2017; Zapponi et al., 2017). Trees with veteran traits are particularly endowed with a surprising range of companion floral and faunal species. The survival of these biological monuments across multiple dynasties highlights the inherent capacity of sacred sites to serve as “living ecological archives,” preserving a broad complement of genetic diversity and historical ecological memory that have been largely erased from the broader regional landscape (Kowarik et al., 2016; Ormsby, 2021). Consequently, integrating these culturally protected landscapes into national and global conservation networks is essential for capturing the full spectrum of biodiversity, especially in rapidly urbanizing regions where large-scale wilderness areas are no longer viable.

Cultural-religious filtering as a primary driver of temple tree composition

The floristic composition of heritage trees at Nanhua Temple cannot be interpreted solely through the lens of ecological processes. Rather, it reflects a centuries-long process of culturally mediated species selection and preferential protection that has profoundly shaped the site’s botanical profile. As one of the most geographically extensive religious traditions globally, Buddhism has significantly shaped the distribution patterns of tree species across China, leaving an ecological legacy that transcends the immediate spatial constraints of individual sacred enclosures (Liu et al., 2021). The documentation of 184 Buddhist tree species across 246 temples in China establishes religious utility as a fundamental driver for both taxonomic selection and geographic expansion (Jin et al., 2025). The constituent cultural influence operates through a mechanism independent of environmental filtering and, in certain instances, sufficient to override the ecological constraints of the local habitat. The co-occurrence at Nanhua Temple of species spanning both the canonical “five trees and six flowers” of Buddhist scripture and locally native subtropical forest taxa thus reflects two synergistic selection pressures (Wang et al., 2020): the transplanted cosmology of South Asian Buddhism, adapted and localized through centuries of cultural practice in the host country, and the intrinsic ecological context of the Nanling subtropical forest biome.

This dual filtering is particularly evident in the presence of F. religiosa, the sacred bodhi tree under which Siddhartha Gautama is traditionally believed to have attained enlightenment. The tree was spread in tandem with Buddhism into China. Therefore, its presence at Nanhua Temple represents the intentional cultivation of an exotic tree rather than natural establishment. As a tropical species, F. religiosa has reached the northern limits of its climatic tolerance in north Guangdong Province. The further northward spread of Buddhism entered temperate latitudes, where winter is too cold for F. religiosa. As a pragmatic response to ecological reality, the cultural assimilation of alternative Buddhist botanical symbolism in China involved the systematic selection of native species with suitable ecological and iconographic traits as substitutes for the original tropical canonical taxa (Jin et al., 2025). This process of biocultural substitution has established a distinctive temple floristic signature that integrates regional native biodiversity with translocated cultural species, thereby maintaining symbolic continuity across diverse environmental gradients (Bhagwat and Rutte, 2006; Dudley et al., 2012).

For instance, G. biloba is widely adopted as a substitute for F. religiosa in central and northern China to symbolize awakening (Chen and Fan, 2013). The long-living and tenacious species occurs alongside the original bodhi species at Nanhua, reflecting the transitional climatic zone in north Guangdong, where both can coexist. Beyond serving as a means of addressing ecological limitations, the substitution echoes a desire to assimilate suitable local flora into the spiritual realm. Similarly, C. officinarum and G. pensilis are deeply embedded in both Taoist and Buddhist traditions as symbols of longevity, purity, and incorruptibility, driving their preferential cultivation and protection across Chinese temple landscapes (Lu, 2020). The dominance of culturally sanctioned species within the heritage tree assemblage at Nanhua Temple represents the legible botanical trace of over a millennium of intentional biocultural stewardship. The localized arboreal landscape denotes a form of intentional ecological management rooted in religious motivation. Collaterally, the process yields serendipitous conservation outcomes comparable to those achieved through formal biodiversity programs (Rath et al., 2020; Moore and Atherton, 2021; Sinthumule, 2024).

This insight provides significant theoretical implications, suggesting that the species composition of temple landscapes represents an actively constructed biocultural artifact rather than a passive byproduct of protection. Such diverse, if not unique, assemblages are shaped by religious iconography, pilgrimage networks that facilitate germplasm exchange, and aesthetic preferences of successive generations of monastic communities. The time-honored tradition of monks visiting other temples provides opportunities for the exchange of plant seeds and seedlings amongst temples along the pilgrimage circuit (Maud, 2017). Such personnel exchanges can lead to assisted migration and the intentional introduction of plants, as well as to the sharing of a common pool of plants at religious sites at different geographical locations. Recognizing this latent agency in floristic composition facilitates new research into religious institutions as long-term agents of species translocation, diversity maintenance, and accidental ex situ conservation for rare taxa.

Sacred landscapes as refugia for rare and threatened species: the case of Glyptostrobus pensilis

Beyond their role in maintaining culturally favored taxa, sacred Buddhist landscapes have functioned as inadvertent repositories for rare, relict, and threatened species that have been systematically eliminated from surrounding intensively managed landscapes (Mohanty et al., 2016; Xie et al., 2025b). The most compelling evidence for this function at Nanhua Temple is the persistence of three Tier-1 G. pensilis (Cupressaceae) individuals, the site’s oldest trees. It is a monotypic genus endemic to East Asia and one of the most globally threatened tree species, classified as Critically Endangered (CR) on the IUCN Red List and designated as a First-Class National Protected Plant under Chinese law (Li et al., 2004; Thomas et al., 2020). This ancient relict gymnosperm was once widespread across subtropical China but has been reduced to scattered, fragmentary wild populations by millennia of land-use change, timber extraction, and wetland drainage (Tang et al., 2019). The persistence of three individuals aged 500 years or more at Nanhua Temple surpasses the longevity documented for any surviving wild population (Tang et al., 2019). They provide compelling evidence that sacred site protection can sustain viable populations of critically threatened tree species over exceptionally long temporal scales, a feat that conventional conservation approaches rarely achieve.

The heritage-tree pattern echoes findings from analogous systems worldwide. In the fragmented Ethiopian Highlands, church forests preserve remnants of the original Afromontane vegetation and serve as important in situ refugia for indigenous woody species lost from surrounding agricultural landscapes (Teku et al., 2024). Sustained by religious traditions and cultural taboos, these sacred forests conserve substantial regional plant diversity and maintain key ecosystem functions in heavily degraded environments (Klepeis et al., 2016).

In Japan, sacred forests include satoyama and chinju no mori. Satoyama refers to the traditional Japanese rural landscape with juxtaposed patches of natural and cultural land uses forming a mosaic of managed forests, rice paddies, farmsteads, and irrigation ponds, situated between mountain foothills and arable flatlands. Chinju no mori refers to forests established and maintained in or around Shinto shrines. These intimately associated natural-cum-cultural landscapes often preserve remnants of old-growth vegetation, including large native trees that have disappeared from surrounding plantation landscapes (Ishii et al., 2010). Many of these sacred forests have remained continuously protected since the establishment of Shinto worship sites, in some cases for more than a thousand years.

In parts of Mediterranean Europe, sacred sites and church graveyards serve as important reservoirs of beta diversity, supporting distinct fungal, invertebrate, and vascular plant assemblages that are often absent or decimated in adjacent managed forests (Frascaroli et al., 2016; Stara et al., 2025). The conservation value of old sacred sites appears particularly important for species associated with standing deadwood, veteran trees, and structurally complex habitats. The global convergence of these findings suggests that the capacity of sacred sites to harbor rare and relict organisms is not a site-specific curiosity but a generalizable endowment of any landscape where long-term cultural safeguard and prohibitions against disturbance have been consistently enforced.

The conservation value of sacred natural sites is closely linked to their exceptional temporal continuity. Long-lived organisms, such as large old trees, require stable site protection over centuries to sustain survival, regeneration, and ecological persistence. In contrast, formal conservation systems are often constrained by relatively short policy and management cycles (Dudley et al., 2012; Lindenmayer et al., 2014). Sustained by enduring religious traditions with deep cultural roots rather than statutory regulation, sacred sites are among the few social institutions capable of sustaining habitat stability over extended timescales. In this context, the surviving G. pensilis individuals at Nanhua Temple signify far more than their individual longevity. They constitute living remnants of a once-widespread subtropical wetland flora that has largely disappeared due to prolonged anthropogenic transformations (Zheng et al., 2011). Their persistence reflects the cumulative effect of centuries of Buddhist stewardship and cultural protection rather than intentional scientific management. These outstanding doyens are too precious to be lost. Their demise could entail not only the disappearance of irreplaceable genetic resources, but also the erosion of a living archive of regional ecological history.

Temple landscapes as integrated hubs of biocultural diversity: toward a conservation network framework

Our findings suggest that sacred Buddhist temple landscapes, particularly historically continuous sites such as Nanhua Temple, should be understood as integrated centers of biocultural diversity, where biodiversity conservation, cultural heritage, and long-term institutional stewardship interact as a holistic and enabling regimen to sustain conservation outcomes that are difficult to achieve through formal protected areas or conventional community management alone. This concept extends beyond the “sacred sites as refugia” framework (Imarhiagbe and Ogwu, 2022; Sinthumule, 2024) by emphasizing the active, generative, and network-embedded nature of temple conservation functions, rather than treating sacred sites merely as passive survivors in a relatively hostile landscape.

The exceptionally high concentration of heritage trees at Nanhua Temple indicates that the temple can function not merely as a site of passive tree preservation, but also as a long-term center for the accumulation and persistence of biocultural diversity (Pungetti et al., 2012). The congregation of old trees confined within a relatively small area suggests that the temple landscape has continuously retained trees that were progressively eliminated from the wider Guangdong region through centuries of logging, agricultural expansion, and land transformations. As a result, the temple now represents a biologically distinctive refuge rather than a residual fragment of the surrounding landscape (Verschuuren et al., 2010). Similar patterns have been documented across Chinese Buddhist and Taoist temples, where the richness and density of heritage trees are closely associated with the historical continuity and cultural status of religious institutions (Huang et al., 2025; Xie et al., 2025b), highlighting the important role of sacred landscapes in conserving long-term arboreal diversity.

Beyond the site scale, sacred temple landscapes may also contribute to regional ecological connectivity. Large old trees play a critical role in seed production, habitat provision, and forest regeneration. Temple forests can therefore function as refugia and dispersal nodes within fragmented human-dominated landscapes (Le Roux et al., 2014; Huang et al., 2023). The heritage tree assemblage at Nanhua Temple, located adjacent to natural hillside forests, occupies a favorable position for ecological connectivity with surrounding vegetation patches and may function as a local propagule source for the restoration of native subtropical forests (Holl, 1999). Strong mother trees can provide propagules to support genetic enrichment of otherwise genetically depleted species in local or regional ecological restoration efforts. Given its location adjacent to natural hillside forests, Nanhua Temple offers a concrete, site-level illustration of how a single sacred landscape might extend its conservation function into the surrounding regional ecological network of northern Guangdong, rather than a basis for generalizing landscape-connectivity planning beyond this specific setting (Ishii et al., 2010; Chanu et al., 2025).

The conservation outcomes observed at Nanhua Temple also underscore the importance of institutional continuity and culturally embedded stewardship in long-term biodiversity protection. Formal protected area systems alone are often insufficient to conserve the full range of biodiversity in densely populated and intensively managed landscapes (Perfecto and Vandermeer, 2010; Imarhiagbe and Ogwu, 2022). In this context, sacred sites with rich natural endowments provide complementary conservation mechanisms grounded in social norms, religious ethics, and community legitimacy rather than solely in statutory regulation. The Nanhua Temple case offers a local empirical perspective on how historically continuous sacred landscapes might contribute to regional biodiversity objectives. Its pattern of long-term, culturally embedded stewardship resonates with the rationale underlying Other Effective Area-Based Conservation Measures (OECMs) (Jonas et al., 2017), which recognize the conservation value of landscapes maintained through sustained cultural practice and community governance rather than statutory protection alone. Nanhua Temple serves as a representative case study that contextualizes the implementation of the Kunming-Montreal Global Biodiversity Framework, revealing key governance, monitoring, and arboricultural challenges in recognizing sacred holy sites as OECMs (Wang and Deng, 2025).

Importantly, the ecological significance of sacred temple landscapes is closely tied to the persistence of the religious traditions and cultural practices that have maintained them over time (Bhagwat and Rutte, 2006; Pungetti et al., 2012; Marini Govigli et al., 2024). The long-term preservation of heritage trees at Nanhua Temple has depended less on formal legal enforcement than on a persistent cultural ethic of respect for life embedded within Chan Buddhist philosophy and maintained through generations of monastic stewardship. Conservation strategies that recognize monasteries and religious communities as active governance partners are therefore likely to achieve more durable outcomes than externally imposed management approaches alone (Hamza et al., 2025). This perspective has wider relevance across Asia, where Buddhist, Taoist, Hindu, and Shinto sacred landscapes collectively form an extensive yet often overlooked network of culturally protected habitats whose cumulative conservation value may rival that of many formally designated protected areas (Salick et al., 2007; Dudley et al., 2012; Jaganmohan et al., 2018; Moore and Atherton, 2021).

Old-growth structural characteristics, ecological functions, and integrated conservation management

The regression analyses and distribution patterns of tree age and DBH (Figures 2a,b) underscore a history of recurrent population recruitment and replacement. In the current population pyramid, the age structure shows a typical broad base of young trees, accompanied by a rapid decline toward older age groups. This pattern is indicative of high mortality, which is continually compensated for by high fecundity. The tree population has remained relatively young due to these inherent demographic dynamics. This trend suggests that the temple environment provides the conditions for reproductive success by facilitating seed production, germination and the growth of recruits to maturity, replacing outgoing members. A tiny cohort of trees with exceptional genetic superiority growing in genial habitats and fortuitously escaping harsh abiotic and biotic stresses could be retained to grow into old, rare and large living monuments. Thus, the site serves as a crucible for nurturing and conserving outstanding elites. Active regeneration provides a continuous supply of feeder trees, which are rigorously screened by nature to select the cream to fill the coveted heritage tree rank.

The size-class distribution and allometric scaling relationships documented in this study indicate that the heritage tree community at Nanhua Temple exhibits structural signatures characteristic of old-growth forest stands. The distribution of individuals across a broad DBH range, the presence of large-statured C. officinarum and L. formosana individuals, and the statistically significant positive relationships between age, DBH, height, and crown width collectively reflect trajectories of ontogenetic development that are systematically suppressed in disturbed or managed landscapes but freely expressed under centuries of institutional protection (Chen et al., 2018). These structural attributes transcend mere description; large, senescent trees, characterized by expansive crowns and complex stem morphologies, function as keystone ecological structures. They harbor disproportionately high levels of biodiversity that are typically absent in younger, structurally simplified counterparts (Sillett and Pelt, 2007; Lindenmayer and Laurance, 2017). The high concentration of these individuals within a mere 0.43 km² site area suggests that Nanhua Temple provides biodiversity and ecosystem services far beyond what its spatial extent would predict. This amplification effect, jointly shaped by ecological and cultural factors, necessitates rigorous empirical quantification in subsequent site-level biodiversity assessments.

While the overall health of the heritage tree assemblage is broadly satisfactory, this study identifies a suite of active threats that collectively reveal a fundamental gap between the robustness of the site's cultural protection norms and the adequacy of its scientific tree management. While the avoidance of anthropogenic felling underscores the durability of Buddhist institutional governance (Liang et al., 2025), various biotic and abiotic stressors pose escalating threats to the population. These include invasive vine infestation, accumulation of incense smoke, termite-induced trunk decay, and progressive physiological decline (Dong et al., 2022). Such pressures demonstrate that passive cultural protection alone is an inadequate conservation instrument for a senescing assemblage of heritage trees (Xie and Jim, 2026). Furthermore, these threats are dynamic rather than static. Under multiple future emission scenarios, climate warming is projected to shift regional hydrothermal patterns (McDowell et al., 2020), potentially subjecting heritage trees to additional physiological stresses that exceed their innate adaptive capacities (Bennett et al., 2015). Such climatic instability threatens the long-term persistence of these ancient individuals regardless of current site-level management efforts.

Based on the observed spatial patterns, health degradation tiers, and dominant stressor categories, we synthesized a structured, three-tiered management framework to transition from emergency physical intervention to long-term monitoring and preemptive care (Table 3). This actionable scheme prioritizes immediate surgical care for imperiled individuals while providing mid- and long-term mitigation pathways for widespread environmental stressors across the temple domain.

Addressing this management gap requires the systematic integration of evidence-based arboricultural science into the temple’s conservation practice, alongside and in support of its existing cultural framework. From a management perspective, this requires implementing a systematic monitoring framework that integrates non-invasive diagnostic technologies. The application of sonic tomography for internal decay mapping, complemented by annual Visual Tree Assessment (VTA) protocols, facilitates early identification of structural anomalies before they progress beyond critical physiological or mechanical thresholds (Hanum et al., 2020). Invasive vine management should be formalized as a seasonally timed priority intervention (David and Lake, 2023), particularly for Tier-1 and Tier-2 trees whose loss would be ecologically and culturally irreplaceable (Blicharska and Mikusiński, 2014). The documented physiological decline attributed to chronic incense smoke exposure necessitates collaborative strategies to abate the impingement developed in conjunction with the monastic community. Potential interventions, including the strategic repositioning of ritual incense burners and improvements to courtyard airflow, can reconcile the preservation of spiritual traditions with the mitigation of cumulative phytotoxic stress on heritage trees. On a broader scale, the temple administration should prioritize developing a long-term tree succession strategy (Melaku and Pastor Ivars, 2025). By proactively fostering a cohort of younger native trees with superior traits, the management can ensure the structural and functional continuity of the heritage assemblage as senescent individuals eventually reach the end of their life cycles. The monastic community, with its established ethos of reverence for life and demonstrated capacity for trans-generational institutional commitment, represents an ideal partner for injecting scientific arboricultural recommendations into culturally embedded, durable management practice.

Finally, several methodological limitations of this study warrant consideration for future research. As a rapid, non-destructive, population-wide health census covering all 285 heritage trees, our field protocol focused on visual diagnostic indicators and stressor classification rather than continuous, quantitative monitoring of micro-environmental physical parameters. Future directions should shift from qualitative rapid diagnostics toward continuous quantitative monitoring. Specifically, integrating wireless sensor networks to track soil physical properties (e.g., bulk density, soil compaction, volumetric water content) and micro-meteorological air quality stations (e.g., ambient SO₂, PM2.5, and temperature gradients near major incense burners) will provide deeper eco-physiological mechanisms underlying stress response and guide precision conservation for sacred heritage trees.

Conclusion

This study quantitatively demonstrates that Nanhua Temple serves as an exceptional refugium for heritage trees, with a population density approximately thousands of times the regional average. The presence of critically endangered relicts, such as G. pensilis, underscores the site’s capacity to sustain high-value biodiversity over multi-century timescales. Our findings indicate that the current floristic composition and population structure are products of a deliberate synergy between long-term institutional governance and regional ecological processes, rather than mere passive persistence of vegetation. However, the emergence of intensifying biological and environmental stressors highlights a critical misalignment between traditional cultural stewardship and modern, evidence-based arboricultural management. To bridge this gap, we propose the systematic integration of non-invasive diagnostics, invasive species suppression, timely arboricultural care and treatment, and proactive succession planning. Ultimately, these results reinforce the global significance of sacred Buddhist landscapes as integral and keystone nodes for biocultural conservation, particularly in rapidly urbanizing Asia, where such reservoirs remain chronically underappreciated.

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