A culture of conservation: How an ancient forest plantation turned into an old‐growth forest reserve – The story of the Wamulin forest

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2021 The Authors. People and Nature published by John Wiley & Sons Ltd on behalf of British Ecological Society 1School of Geographical Sciences, Fujian Normal University, Fuzhou, Fujian, China 2Sanming Experimental Forest, Sanming, Fujian, China 3Administrative Station of Wanmulin Nature Reserve, Jianou, Fujian, China 4Department of Biological Sciences, Florida International University, Miami, FL, USA 5Department of Life Science, National Taiwan Normal University, Taipei, Taiwan


| INTRODUC TI ON
Forest plantations are an important component of global forest cover with a global extent of 294 million ha (FAO, 2020). The global extent of forest plantations increased approximately 139% from 1990 to 2020 (from 123 million ha to 294 ha) despite an overall decrease of global forest area by 178 million ha or 1.7% during that period (FAO, 2020). As a result, maximizing the ecosystem services of forest plantations has become a major objective of forest management in light of current global climate change (Baral et al., 2016;Barrios et al., 2018;Liu et al., 2018).
Forest plantations are often considered as having lower capacities to provide ecosystem services compared to natural forests.
Although many studies indicate that forest plantations can provide multiple forest-based products and play an important role in carbon sequestration (Baishya et al., 2009;De Stefano & Jacobson, 2018;Lai, 2004;Quine, 2015;Sang et al., 2013), there are doubts regarding their relative capacity for long-term carbon sequestration and harboring a comparable diversity of organisms to natural forests (Barlow et al., 2007;Liu et al., 2018;Sohngen & Brown, 2006;Yu et al., 2019). In addition, forest plantations are not often associated with the unique cultural and biodiversity conservation values that characterize many old natural forests (Sutherland et al., 2016;Yazzie, 2007) because the vast majority of forest plantations are relatively young and therefore lack clearly established cultural connections to people.
Old-growth forests differ from forest plantations in many ways. In addition to the astonishing tall and giant trees they have, many old-growth forests are characterized with more complex horizontal and vertical forest structure than second-growth forests, which results in a greater diversity of habitats for plant and animal species (McMullin et al., 2010;Spies & Franklin, 1988;Zenner, 2004). Many old-growth forests are refuge habitats (i.e. areas, often protected, where populations thrive because of low mortality or increased survival or recruitment) for endemic, endangered or keystone species such as the spotted owl of the Pacific Northwestern United States (Yackulic et al., 2019), the ant communities of the Brazilian Atlantic Forest (Bihn et al., 2008), or the giant panda of Sichuan, China (Zhang et al., 2011). Although oldgrowth forests are assumed to have low, even near zero net carbon accrual rates, studies have shown that they can still sequester and accumulate large amounts of carbon in soils (Desai et al., 2005;Zhou et al., 2006) and thus are important global carbon sinks (Badalamenti et al., 2019;Luyssaert et al., 2008;Yuan et al., 2016).
In this light, old-growth forests provide a clear societal and cultural value, given the current anthropogenic global change pressures.
Old-growth forests are symbols of humankind's natural legacy, and hallmarks of societal environmental stewardship. In fact, many old-growth forests are national or world heritage sites, which symbolizes both their cultural and environmental value as natural ecosystems. For example, the old-growth beech Fagus crenata forest in the Shirakami Mountains in Japan was registered as a UNESCO World Heritage in 1993 because it contains some of last unaltered remains of a forest type which once covered the landscapes of northern Japan (Chakraborty, 2018).
Similarly, the large and iconic old-growth forests of British Columbia are symbolic of its natural heritage, exemplifying how native people used the forest for provisioning of food, medicine and shelter (Connell et al., 2015). Thus, although not defined explicitly, old-growth forests are in general, assumed to be the unaltered product of nature's majesty over long periods of time with minimal human disturbance (Bradshaw, 2004;Chapman & McEwan, 2016;Lin et al., 2015).

| FORE S T REG ENER ATI ON AND ECOSYS TEM S ERVI CE S
Forests can regenerate artificially, completely naturally or naturally with some human assistance (Table 1). Artificial regeneration which is most common in the form of forest plantations is achieved by planting and actively managing tree survival and growth for economic gain. The expansion of forest plantations often takes place at the expense of natural forests, which often leads to a reduction in the provisioning of key forest resources, like clean air and water, and increases the risk of environmental degradation, including reduced soil fertility, increased soil erosion, more floods and even desertification (Li, 2004) as well as a loss of connectivity between the forest and the people (Foo, 2016). Some silviculture practices seek to develop or maintain old-growth forest attributes in forest plantations (Bauhus et al., 2009). However, an important but largely unaddressed question in management is whether forest plantations can successionally develop to old-growth forests, with their characteristic high K E Y W O R D S biodiversity, ecosystem services, old-growth forest, secondary succession, unity between humans and the nature, Wanmulin Nature Reserve capacity for providing ecosystem services (e.g. biodiversity, carbon storage and culture values). The answer to this question has important implications in forest management, especially in regions where intensive forest plantation practices have led to land degradation (Bi et al., 2007;Yetti et al., 2011).
Natural regeneration and assisted natural regeneration have been recommended as viable strategies to improve ecosystem service capacities of degraded plantation forests (Chazdon, 2017;Crouzeilles et al., 2020;Shono et al., 2007;Yang et al., 2018). Naturally regenerated forests have been shown to achieve the level of species richness similar to old-growth forests in several decades, but a much longer time is required for them to regain the species composition and structural complexity of typical old-growth forests (Aide et al., 2000;Brown & Lugo, 1990). Regeneration through human assistance to minimize barriers to natural regeneration (e.g. competition with weeds and grazing) has been suggested as a low cost and effective way to quickly restore degraded tropical and subtropical forests in terms of biodiversity, soil and water conservation and carbon sequestration (Evans et al., 2015;Shono et al., 2007Shono et al., , 2020Yang et al., 2018). Secondary forests developed through assisted natural regeneration have been shown to provide multiple social benefits in addition to ecological benefits (Chazdon & Uriarte, 2016).
In relatively 'wild', well-conserved areas with minimal direct human influence, regeneration through secondary succession takes place typically following major disturbance events such as the 1988 Yellowstone National Park fire (Turner et al., 1997). Given sufficient time, many of the disturbed (e.g. burned) sites may naturally regenerate to old-growth forests characteristic to the region although they could be slightly different in their extent, spatial distribution or species composition from the forest existing before the fire due to changes in the environment such as the climate (Donato et al., 2016).
Natural regeneration through secondary succession can sometimes take place not as the result of conservation effort, but due to lack of management such as old field abandonment (Aide et al., 2000). In fact, modern successional theory has its origins in studies of secondary succession on abandoned old fields in the eastern United States (Inouye et al., 1987;Nicholson & Monk, 1974).
One important but not well-addressed question is whether forest regeneration through secondary succession on unmanaged lands can result in the recovery of forests with characteristics common to old-growth forests. A study of secondary forests in central Panama ranging in age from 20 to 100 years showed that secondary forests increased in ecological similarity to old-growth forests over time in terms of shade tolerance but not in species composition (Dent et al., 2013). Similarly, the study of secondary succession following old field abandonment and the study of historical changes in forest vegetation and land use in central New England indicate that species richness but not species composition in 150-to 200-year-old forests were similar to old-growth forests (Foster et al., 1998;Nicholson & Monk, 1974). These studies support the idea that 100-200 years is not sufficient to attain forests with old-growth characteristics. However, to our knowledge no studies have examined secondary forests of more than 200 years old to evaluating whether the forest will eventually develop old-growth characteristics and attain a high capacity for providing ecosystem services over multiple centuries.
Here we describe a case study, in which a 'human-made forest' in southeastern China has successionally developed over six centuries to become an old natural forest with extraordinarily high levels of biodiversity, large carbon stocks and a deep cultural significance.
We argue that although human disruption is currently the main cause of the disappearance of many old-growth forests, the many species that inhabit them, and the cultural links between human communities and the forest, such disruptions are not the only possible outcome. If well-managed or protected, marginal land can develop into an old natural forest with characteristics similar to primary old-growth forests; however, this process takes a very long period of time, likely multiple centuries. We also highlight that the successful protection of the forest, despite recent economic growth at the expense of natural forests, relies on both the deep cultural belief of the unity between the nature and people and the inclusion of the forest into the formal nature reserve system. Thus, we affirm that the protection of local culture and its incorporation into national nature reserve system are key to the protection of sacred forests with often unique ecosystem services.

| The history
The 189-ha Wanmulin Nature Reserve, is a Fengshui (an ancient Chinese geomantic tradition which claims to use energy forces to harmonize environments) forest. It was a marginal land area used as a cemetery of the Yang family (Chen, 2000), and during this time was not forested. During a famine in 1,354, Mr Fushing Yang (1,305-1,378)-an elite of the Yang family, gave one Chinese bushel (approximately 10 L) of millet to people suffering from the famine and, in exchange, he asked each of them to plant one Chinese fir Cunninghamia lanceolata sapling in his family graveyard (Chen, 2000;Qiu, 2010). This exchange (bushels of millet for the planting of trees) had two important purposes. For one, Mr Yang delivered the message that there is no free lunch; more importantly, this eased doubts from the government that donating food to the poor people was a sign of suspicious economic activity (Qiu, 2010;Yu, 2001 (Qiu, 2010). This is the only known large scale tree harvest to the forest plantation since its establishment.
In 1,399, after Mr Jong Yang, the grandson of Mr Fushing Yang passed the imperial examination at the provincial level, the site was locked down as a protected area by the provincial government (Yang, 2004). Since then, land development or felling trees in the forest has been forbidden. In 1954, the forest was designated as

| FORE S T S TRUC TUR AL CHAR AC TERIS TIC S
Six major plant communities dominated by tree species common and native to the region can be identified within the Wanmulin Nature Reserve (Zhu et al., 1997). By 1997, the canopy height of the six plant communities ranged from 23 m to 32 m, with maximum diameters at breast height (dbh) of the dominant tree species ranging from 46.7 cm to 100.5 cm, and tree ages spanning 120 ± 20 years to Reserve was initiated as a human-made Chinese-fir plantation but is now an ~600-year old mixed-species forest with many old-growth forest characteristics and a high capacity to provide essential ecosystem services. Photo courtesy of Xiaohui Guan J-shaped (Bi et al., 2003), which is common for old-growth forests (McCarthy & Weetman, 2006;Rozas, 2006;Varga & Klinka, 2001), although other distribution types such as negative exponential model and Weibull functions could also be found in old-growth forests (Westphal et al., 2006). Canopy gap size also has a reverse J-shape frequency distribution with a mean gap size of 75 m 2 , but gap size varies widely, ranging from <60 m 2 to >800 m 2 (Yan et al., 2002). A wide range of gap size has been suggested to contribute to high canopy species diversity of southern Appalachian cove old-growth forests of Kentucky and Tennessee, United States (Clebsch & Busing, 1989). Gap phase dynamics, which contributes to the population age/size-structure of old-growth forests (Rebertus & Veblen, 1993), play a key role on the regeneration of the Wanmulin Nature Reserve as seedlings of many of the tree species found in the forest (29 species in total) only regenerate in canopy gaps .

| Plants and large fungi
There

| Biomass/carbon storage
The above-ground biomass of trees in the Wanmulin Nature Reserve is around 400 Mg/ha, and based on a carbon concentration of 55.5%, the above-ground carbon stock is estimated to be around 224 Mg/ha (Huang et al., 2011). The above-ground biomass is much higher than other forests in China. According to a nationwide survey, the average above-ground biomass of all forests in China is 120 Mg/ha, and maximizing at >300 Mg/ha with subtropical evergreen broadleaf forests harboring about 140 Mg/ha (Su et al., 2016). Based on the survey of Su et al. (2016), the tropical monsoon forests-rainforests have the highest above-ground biomass in China, with more than 50% at the range of 100-250 Mg/ha. In the region, the above-ground biomass of a natural evergreen broadleaf forest in the Gutianshan National Nature Reserve of Zhejiang Province is 180-246 Mg/ha (Lin et al., 2012). Therefore, like many old-growth forests, the old forests within the Wanmulin Nature Reserve play an important role in cycling and storing carbon (Hoover et al., 2012;Luyssaert et al., 2008;Paw et al., 2004).
In terms of below-ground carbon, soil organic carbon of the Wanmulin Nature Reserve is 157 Mg/ha, 34% higher than adjacent secondary forests and more than two times the soil organic carbon stocks in nearby arable land (Yang et al., 2009). It is also considerably higher than the 100-114 Mg/ha reported for subtropical broadleaf forests in China (Li & Zhao, 2001).

| CULTURE AND EDUC TIONAL VALUE S AND ECOSYS TEM S ERVI CE VALUATI ON
The act of Mr Yang from more than 600 years ago, highlights the long-held Chinese belief of 'unity between humans and the nature', as well as the lesser-known Yang family value that 'tree prosperity leads to family prosperity' (Yu, 2001). The specific belief is emotional or even spiritual in nature, encompassing the assumption that trees grow well because of good land stewardship, and good stewards of land are also good family members. Following these beliefs, the an- USD annually, 41.4% of which comes from soil protection and improvement, 29.3% of which originates from air purification, 13.5% of which is related to water resource protection, 12.4% of which comes from timber products (estimated from the current market value of current timber divided by 600 years, as harvest has been forbidden since 1,399), and 3.6% of which is related to forest landscape attraction (Yu, 2001).

| WANMULIN NATURE RE S ERVE IN COMPARISON WITH OTHER SACRED FORE S TS AND UNINTENTIALLY PROTEC TED FO RE S TS
Forests can be largely free from direct human influence for both intentional and unintentional reasons ( Table 4). The formal conservation of forests with laws and conservation easements is well understood. However, in the absence of laws and conservation easements, the lack of direct human influence on natural areas which leads to secondary succession and forest development can arise intentionally, (i.e. as a result of cultural or religious beliefs) or unintentionally (i.e. unplanned, as in the case of old field abandonment or in remote, inaccessible areas) because there is no need to manage the forests yet (Peterken, 1996) and forest structure in the sacred forests of Meghalaya, India, which are much better conserved than adjacent unprotected forests (Tiwari et al., 1998). In addition to intentional protection by religious or culture beliefs, forests in national parks and nature reserves are intentionally protected by laws for conservation purposes. Although the formal protection by conservation legislation is of relatively recent origin (within the last 200 years), the forests protected often have much longer periods free from direct human disturbance because wildness or pristineness is one of the main reasons they were chosen for protection by laws. Their protection reflects intentional human efforts to keep certain areas of nature from the anthropogenic forces that are transforming them (Turner, 2014), and provides a link between intentional conservation and formal (i.e. legal) conservation areas. Such conservation efforts are rewarding, as national parks and other protected areas have been shown to be keystones to conservation and sustainable development (Nelson & Serafin, 2013).
Natural forests with minimum human influences represent an important reference point for evaluating human impact on natural ecosystems and for illustrating the interconnection between people and the natural woodlands (Peterken, 1996).
The Wanmulin Nature Reserve and many other sacred forests, globally, are unintentionally protected due to culture beliefs but not necessarily by laws, at least at the beginning. Like the Wanmulin Nature Reserve, many scared forests across the globe are key reservoirs of biodiversity and have high cultural value (Ambinakudige & Sathish, 2009;Ormsby, 2011;Rots, 2017). For example, sacred forests in the Himalayan of southwest China are keystone habitats to bird conservation efforts (Brandt et al., 2013). In addition to the culture and religious significance, more than 100,000 sacred forests in India are important refuge habitats for biodiversity conservation, with some of them being international biodiversity hotspots (Ormsby & Bhagwat, 2010).
Sacred sites protected through community-based conservation due to religious and cultural beliefs are found on every continent except Antarctica and have been considered an important component of global biological conservation (Bhagwat & Rutte, 2006). Without formal protection by laws, changes in the cultural or religious beliefs of the nearby communities in combination with the pressures from the demands for forest-derived natural resources (e.g. timber products) and for agriculture, industrial, commercial or residential development impose threats to these forests (Ormsby & Bhagwat, 2010).
It has been suggested that if local communities depend heavily on the forests to meet their needs, sacredness may not be sufficient to ensure their persistence or sustainable use (Soury, 2007).
Using the Wanmulin Nature Reserve as a case study, we illustrate that although cultural traditions were key to the protection of the Wanmulin Nature Reserve for multiple centuries, its inclusion to the nature reserve system granted and ensures its continuing protection via a formal conservation easement despite the increasing competing demands of land use in recent decades.
In contrast to the intentional protection of forests which reflects people's appreciation of the value of nature, many natural forests and second-growth forests in remote areas or developing from abandoned old fields are free from direct human disturbance because of the limited profit of managing them (i.e. unintentionally; Peterken, 1996). Many forests, which have naturally regenerated from abandoned old fields now provide a diverse range ecosystem services such as habitat for biodiversity and large carbon sequestration and storage capacity (Geddes et al., 2011;Johnston et al., 1996;Perring et al., 2012). Such unintentional conservation of forests is possible, and more-probably, in regions with large land areas relative to human population densities, such as parts of the United States of America (Johnson et al., 1991;Li et al., 2016;Pickett, 1982) and the alpine Andes (Sarmiento et al., 2003).
However, without changes in the human valuation of the natural forests, they will continue to be converted to more profitable land uses, especially related to private or corporate interests. For example, in New England, the expansion of secondary forests took place from the mid-1800s until the 1990s following an abandonment of farmland (Foster et al., 1998), but between 1990 and 2005, a total of 133,000 ha of land has be deforested for residential or commercial development (Jeon et al., 2014).

| IMPLIC ATIONS ON THE REL ATIONS HIP B E T WEEN PEOPLE AND NATURE IN THE ANTHROP O CENE
Human beings, and societies as their collective, have unprecedently altered global ecosystems, leading to degraded ecosystems with reduced levels of ecosystem services (Western, 2001). This phenomenon is one defining characteristic of the Anthropocene (Malhi, 2017).
Restoration of degraded forests, especially tropical forests, is a major goal for current global forest management (Lamb et al., 2005). It has been suggested that 'Aligning restoration goals and practices with natural regeneration can achieve the best possible outcome for achieving multiple social and environmental benefits at minimal cost' (Chazdon & Guariguata, 2016 We have described a case study in which an ancient forest plantation was protected yet unmanaged, thereby allowing natural regeneration to take place, which resulted in a forest with many characteristics of an old-growth forest, including high biodiversity levels, even aged trees, and a highly variable gap size distribution. The Wanmulin Forest is also characterized by large carbon stocks (both below-ground and above-ground), cultural significance and many ecosystem services of high economic value. Thus, although anthropogenic activity is a main cause for the disappearance and degradation of many old-growth forests around the globe, it is not the only possible outcome. If current second-growth forests are well protected, they have the potential to develop into old forests with characteristics similar to primary old-growth forests and extraordinarily high capacities for providing ecosystem services.
However, it takes a long period of time to attain such old-growth forest attributes, most likely more than a few centuries. Thus, it is unwise to interpret the example of the Wanmulin Nature Reserve to claim that forest plantations are ecologically and culturally as valuable as old-growth forests, because it is the multiple centuries of natural succession without human disturbance, not the establishment of forest plantation, that contributes most to the high levels of ecosystem services found in the Wanmulin Nature Reserve.

ACK N OWLED G EM ENTS
This study was supported by grants from National Natural Science Hongda Zeng for the production of Figure 1.

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest. Neither Dr Zhijie Yang nor Dr Yuesheng is from the Yang family that owned the Wanmulin forest.

AUTH O R S ' CO NTR I B UTI O N S
T collected the paper and took the pictures. All authors contributed to the drafts and gave final approval for the submission.

DATA AVA I L A B I L I T Y S TAT E M E N T
Sources of all data used in this paper are clearly identified.