Diversity and density patterns of large old trees in China

Species diversity and spatial pattern of heritage trees in Taiyuan

Heritage trees are key to maintaining biodiversity, supporting ecosystem services, and preserving cultural heritage. This study investigates the species composition, spatial distribution patterns, and conservation needs of heritage trees in ancient Taiyuan city in Northern China, focusing on their cultural-ecological significance and urbanization threats. Using redundancy analysis, we surveyed 4737 heritage trees across ten urban core, suburban and rural districts and nine habitat types and calculated their importance values, species diversity indices, and statistical associations with key socio-demographic and environmental factors. The prized stock comprised 57 species, dominated by Ziziphus jujuba, Styphnolobium japonicum, accompanied by four subdominants such as Platycladus orientalis and Pinus tabuliformis, and 39 uncommon to rare species, contributing considerably to species diversity. Spatial analysis and ecological assessments found distinct distribution patterns, with suburban and rural areas accommodating higher tree abundance and species richness than more urbanized districts. Factors such as altitude, cultivated area, economic activities, and particularly urban development, strongly influenced tree distribution. We analyzed their natural-cum-cultural value and threats from fast urban expansion, habitat fragmentation and loss, and insufficient conservation efforts. The findings underscored the urgent need for targeted and reinforced conservation strategies to safeguard these heritage trees, sustaining their precious legacy for future generations.

Niche Evolution and Conservation of a Chinese Endemic Genus Sinojackia (Styracaceae)

Climate change and human activities are expected to have a profound impact on the distribution of species, especially for narrowly distributed species. Sinojackia is endemically distributed in China, and all species are listed under Chinese protected wild species. Here, we reconstructed the phylogeny and estimated the divergence time of Sinojackia based on whole plastomes, conducted the niche evolution, and predicted the potential habitat area of Sinojackia from the LGM to the future. Our results strongly supported the monophyly of Sinojackia based on whole plastomes. This genus originated in the middle Miocene and diversified since the late Miocene. The aridity index was the highest significant factor for its niche evolution, and the niche evolution rate increased slowly since its divergence. The precipitation of the warmest quarter was a main environmental variable affecting the distribution of Sinojackia in the LGM, while the human footprint is the main variable in the near-current era and 2081-2100. Compared to the current distribution of Sinojackia, the highly suitable distribution area contracted in the LGM, but expanded during 2081-2100. This study provides potential areas for the in situ conservation of Sinojackia.

A Treasure Trove of Urban Microbial Diversity: Community and Diversity Characteristics of Urban Ancient Ginkgo biloba Rhizosphere Microorganisms in Shanghai

Rapid urbanization has exerted immense pressure on urban environments, severely constraining the growth of ancient trees. The growth of ancient trees is closely linked to the microbial communities in their rhizospheres, and studying their community characteristics may provide new insights into promoting the growth and rejuvenation of ancient trees. In this study, the rhizosphere soil and root systems of ancient Ginkgo biloba trees (approximately 200 years old) and adult G. biloba trees (approximately 50 years old) in Shanghai were selected as research subjects. Phospholipid fatty acid (PLFA) analysis and high-throughput sequencing were employed to investigate the diversity of microbial communities in the G. biloba rhizosphere. The results indicated that the 19 PLFA species selected to characterize the soil microbial community structure and biomass were present in the rhizosphere soil of both ancient and adult G. biloba trees. However, the total microbial biomass and the microbial biomass in the rhizosphere soil of ancient G. biloba were lower than the microbial biomass in the rhizosphere soil of adult G. biloba. The biomasses of Gram-negative bacteria (G-), arbuscular mycorrhizal fungi (AMF), and protozoans (P) were significantly different. Total phosphorus, organic matter, and pH may be the key factors influencing the soil microbial community in the rhizosphere zone of ancient G. biloba. An in-depth study of AMF showed that the roots and rhizosphere soil of G. biloba contained abundant AMF resources, which were assigned to 224 virtual taxa using the MaarjAM reference database, belonging to four orders, ten families, and nineteen genera. The first and second most dominant genera were Glomus and Paraglomus, respectively. Archaeospora and Ambispora were more dominant in the rhizosphere than the roots. Furthermore, the abundance of live AMF was significantly higher in ancient G. biloba than in adult G. biloba. Therefore, future research should focus on the improvement of soil environmental characteristics and the identification and cultivation of indigenous dominant AMF in the rhizosphere of ancient G. biloba, aiming for their effective application in the rejuvenation of ancient trees.

Latitudinal variation and driving factors of above-ground carbon proportion of large trees in old-growth forests across China

Large trees play a vital role in forest carbon stocks, dominating the distribution of community biomass. However, climate change and deforestation are reducing large trees globally, resulting in regional differences in their contribution to carbon stocks. Here, we examined the latitudinal change pattern and drivers of large trees' contributions to stand carbon stocks. Above-ground carbon storage was calculated for 530 plots in old-growth forests across China. Linear regression was used to calculate latitudinal variation in the proportion of above-ground carbon in large trees (i.e., AGC proportion). Variance partitioning and multiple linear regression were used to calculate the relative importance of species diversity, stand structure, functional traits, and environmental factors to AGC proportion. The study found that AGC proportion decreased with increasing latitude, averaging at 64.44 %. Stand structure, particularly the coefficient of variation of DBH, was identified as the key drivers of the AGC proportion. The number of common species (Hill's 1D) had no direct effect on the AGC proportion, while wood density, maximum tree height, and leaf nitrogen-to‑phosphorus ratio showed negative effects. The mass-ratio effects on AGC proportion were stronger than diversity effects. Climate variables primarily affected the AGC proportion through stand variables. These results indicate that simultaneously managing high diversity and AGC proportion may pose challenges. Moreover, considering the substantial contribution of large trees to carbon stocks, their storage capacity and sensitivity to environmental changes exert significant control over forest carbon cycles. Therefore, preserving and enhancing the carbon sink function of old-growth forests in the face of climate change and disturbance may depend primarily on protecting existing large trees and soon-to-be large-diameter trees.

Plant secondary metabolites involved in the stress tolerance of long-lived trees

Ancient trees are natural wonders because of their longevity, having lived for hundreds or thousands of years, and their ability to withstand changing environments and a variety of stresses. These long-lived trees have sophisticated defense mechanisms, such as the production of specialized plant metabolites (SPMs). In this review, we provide an overview of the major biotic and abiotic stresses that long-lived trees often face, as well as an analysis of renowned ancient tree species and their unique protective SPMs against environmental stressors. We also discuss the synthesis and accumulation of defensive SPMs induced by environmental factors and endophytes in these trees. Furthermore, we conducted a comparative genomic analysis of 17 long-lived tree species and discovered significant expansions of SPM biosynthesis gene families in these species. Our comprehensive review reveals the crucial role of SPMs in high resistance in long-lived trees, providing a novel natural resource for plant defense, crop improvement and even the pharmaceutical industry.

Giants of the Amazon: How does environmental variation drive the diversity patterns of large trees?

For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for example, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the diversity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high diversity of large trees. By contrast, variables associated with resources tend to govern tree diversity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high diversity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species diversity. Finally, we mapped general patterns of tree species diversity in the Brazilian Amazon, which differ substantially depending on size class.

Human activities and species biological traits drive the long-term persistence of old trees in human-dominated landscapes

Old trees have many ecological and socio-cultural values. However, knowledge of the factors influencing their long-term persistence in human-dominated landscapes is limited. Here, using an extensive database (nearly 1.8 million individual old trees belonging to 1,580 species) from China, we identified which species were most likely to persist as old trees in human-dominated landscapes and where they were most likely to occur. We found that species with greater potential height, smaller leaf size and diverse human utilization attributes had the highest probability of long-term persistence. The persistence probabilities of human-associated species (taxa with diverse human utilization attributes) were relatively high in intensively cultivated areas. Conversely, the persistence probabilities of spontaneous species (taxa with no human utilization attributes and which are not cultivated) were relatively high in mountainous areas or regions inhabited by ethnic minorities. The distinctly different geographic patterns of persistence probabilities of the two groups of species were related to their dissimilar responses to heterogeneous human activities and site conditions. A small number of human-associated species dominated the current cohort of old trees, while most spontaneous species were rare and endemic. Our study revealed the potential impacts of human activities on the long-term persistence of trees and the associated shifts in species composition in human-dominated landscapes.

Environmental Factors Driving the Spatial Distribution Pattern of Venerable Trees in Sichuan Province, China

Venerable trees are important natural resources and cultural heritage, offering historical, ecological, social and economic value. However, global warming and anthropogenic activities have threatened their welfare and survival. A comprehensive understanding of their current and future spatial patterns, vis-á-vis environmental conditions, can inform the co-management of sustainable resource use and conservation. We employed the existing spatial occurrence data and environmental variables (bioclimate and elevation) to simulate the optimal habitats for venerable trees in China's Sichuan Province. We evaluated the current and future climate scenarios of 2100 with double CO₂ concentration. The BIOCLIM and QGIS spatial analyses assessed the primary factors of geographical distribution. The results identified 10,720 venerable trees from 123 species, 81 genera and 42 families. Cupressus funebris dominated, with the maximum importance value, followed by Ginkgo biloba, Ficus virens var. sublanceolata, and Phoebe zhennan. The elevation distribution of tree abundance and species richness demonstrated a unimodal pattern, skewing to the low-elevation end, with a concentration in the 600-1500 m low-medium altitude. The majority of trees and excellent habitats were found in eastern Sichuan with a less harsh terrain and climate. The bio3 (isothermality) and bio7 (temperature annual range) factors significantly influenced tree occurrence. Temperature imposed a greater effect on distribution than moisture under the current climate scenario. For the future climate-change scenario, the suitable habitats were predicted to maintain an overall stable pattern, with largely contiguous expansions of better habitats. However, climate warming would shrink the excellent habitats on the plains. The findings can inform strategies and guidelines for venerable-tree conservation in Sichuan. Furthermore, vulnerable areas could be identified. The future range expansion sites could be enlisted to cultivate new trees to replenish the venerable-tree pool. Habitat patches that remain sustainable could provide refugia with the potential for protected-area designation.

Effects of Self-Rated Health Status on Residents' Social-Benefit Perceptions of Urban Green Space

Urban green spaces (UGS) provide many social benefits and improves residents' wellbeing. Studying residents' perceptions of UGS's social benefits and driving factors could promote public health and environmental justice. A questionnaire survey of 432 Beijing residents and statistical tests assessed the impacts of residents' living environments and self-rated health status on UGS perceptions. The results showed: (1) perceptions of UGS' physical health benefits were subdued, with an inclination towards other social benefits. Respondents more highly perceived accelerating patient recovery and reducing morbidity and mortality rates. Perceptions of bearing larger-head babies with higher weight were relatively low. For other social benefits, perceptions of improving the environment and life quality were higher, but reducing anger outbursts and resolving conflicts were lower. (2) Childhood living environments did not affect perceptions of social benefits, but current living environments did. Suburb residents understood reducing pain-relief medication demands and bearing larger-head babies better than city residents. City residents understood UGS' investments considerable and sustained returns better than village residents. City residents agreed with accelerating patient recovery higher than village ones. (3) Respondents with "poor" self-rated health status had better perceptions of other social benefits. Those with "excellent" ratings did not fully understand UGS' physical health benefits. "Poor" ratings understood improving a city's image and making cities livable and sustainable better than "good" or "fair" ratings. "Excellent" ratings had less understanding of larger-head babies than "good" or "fair" ratings. The study could enhance appreciation of UGS' social benefits to facilitate planning and management to meet residents' expectations.

Spatial Distribution and Driving Factors of Old and Notable Trees in a Fast-Developing City, Northeast China

As a symbol of urban civilization and history, old and notable trees (ONTs) are facing challenges brought by rapid urbanization. Changchun is the fastest growing city in Northeast China, and throughout its development process of over 100 years it has preserved many ONTs. This study investigated all the ONTs in Changchun, and analyzed the species diversity, spatial distribution characteristics, dimension, age, and health status of trees by using ecological index and mathematical statistics, and trying to find out the underlying factors regulating their distribution. The results showed that there were 773 old trees belonging to 25 species and 2 notable trees from 1 species in Changchun. Pyrus ussuriensis was the dominant species, followed by Salix matsudana and Ulmus pumila. The urban area, population density, greening rate, and construction history did not influence the species and quantity of ONTs, while the types of land use and tree protection planning were important factors affecting the richness, diversity, and growth conditions of trees. To explore the potential reasons for their existence, the ONTs’ data in Changchun was compared with two nearby cities—Harbin and Shenyang. The comparison indicated that the geographical location and climatic conditions also controlled the distribution of ONTs. The number and dimensions of trees were driven by the history and development process of the city. Our findings suggested that preserving favorable living environments and maintaining a low intensity of human disturbance are critical factors for the survival of ONTs in cities.

Old Sacred Trees as Memories of the Cultural Landscapes of Southern Benin (West Africa)

Large old trees (LOTs) are emblematic elements of the cultural landscape and can live for hundreds of years. They represent an intermediate aspect of cultural heritage, linking spirits and humans. They can also provide a range of ecosystem services. In spite of their importance, declining numbers have been reported. This study examined the diversity of LOTs and the impact of anthropogenic threats on their preservation in three districts of southern Benin: Ketou and Abomey, which represent historical districts with royal courts, and Lokossa, which does not have a tradition as a dynastic seat. Semi-structured interviews focused on ethnobotanical aspects and storytelling were conducted with a total of 150 community leaders and traditional practitioners; these were coupled with an inventory of LOTs to demonstrate their importance in maintaining the heritage and providing ecosystem services in cultural landscapes. Diversity, cultural importance, and ethnobotanical indices were calculated to compare positive and negative attitudes towards LOTs by the local people of the study areas. A total of 270 LOT individuals belonging to 14 species were recorded. The most common species was Adansonia digitata (70 individuals), followed by Milicia excelsa (47 individuals), Ceiba pentandra (37 individuals), and Blighia sapida (25 individuals). Sacred forests and the royal palaces (ten for Abomey and three for Kétou), which are protected by a traditional veto, had the highest number of LOTs (145 individuals) belonging to nine species. Details of 79 specific uses were documented for each plant part of LOTs. The most frequently reported were related to medicinal (80.64%), cultic (16.65%), and craft uses (2.6%). Based on a standard area of 100 km2, mean Shannon diversity (H’) and evenness (J) were lower in the cultural landscape of Ketou (H′ = 0.26 ± 0.42; J = 0.23 ± 0.37) compared to Lokossa (H′ = 0.27 ± 0.32; J = 0.21 ± 0.24) and Abomey (H′ = 0.42 ± 0.37; J = 0.35 ± 0.31). The threat patterns suggest that, irrespective of the species involved, certain determining factors (urbanization (35%), the timber trade (18%), and decisions made during the Marxist–Leninist revolution in Benin in 1972 (11%)) have affected and continue to affect LOT abundance and diversity. For better management of LOTs, there is a need to promote decision-making strategies that better align human cultural values and ecological objectives.

Age and spatial distribution of the world's oldest trees

Extremely old trees have important roles in providing insights about historical climatic events and supporting cultural values. Yet there has been limited work on the global distribution and conservation of these trees. We extracted information on 197,855 tree cores at 4,854 sites, and combined it with other tree age data from a further 156 sites, to determine the age of the world's oldest trees and quantify the factors influencing their global distribution. We found that extremely old trees >1,000 years are rare. Among 30 individual trees that exceeded 2,000 years old, 27 occurred in high mountains. Our model suggests that many of the existing oldest trees occur in high-elevation, cold and arid mountains with limited human disturbance. This pattern is markedly different from that of the tallest trees, which are more likely to occur in more mesic and productive locations. Global warming and expansion of human activities may induce rapid population declines of extremely old trees. New strategies, including targeted establishment of conservation reserves in remote regions, especially those in western Table 1 parts of China and USA, are required to protect these trees. This article is protected by copyright. All rights reserved.

Habitat-tree protection concepts over 200 years

The protection and sustainable management of habitat trees is an integral part of modern forest nature conservation concepts such as retention forestry. Bats, cavity-nesting birds, arboreal marsupials, and many different saproxylic species depend on habitat trees and their great variety of microhabitats and old-growth characteristics. With a focus on insights from temperate forests, we traced the development of habitat-tree protection over 200 years. The idea was first conceptualized by foresters and natural scientists in the early 19th century. At that time, utilitarian conservation aimed to protect cavity trees that provided roosts and nesting holes for insectivorous bats and birds. By the second half of the 19th century, habitat-tree protection was well known to foresters and was occasionally implemented. Knowledge of the protection of large old trees, a special kind of habitat tree, for sociocultural and aesthetic reasons developed similarly. But, many foresters of that time and in the following decades fundamentally rejected protection of habitat trees for economic reasons. Beginning in the 1970s, forest conservation and integrative forest management became increasingly important issues worldwide. Since then, the protection of habitat trees has been implemented on a large scale. Long-term views on the development of conservation concepts are important to inform the implementation of conservation today. In particular, historical analyses of conservation concepts allow the testing of long-term conservation outcomes and make it possible to study the resilience of conservation approaches to changing social or ecological conditions. We encourage all conservation ecologists to assess the practical and conceptual impact of the initial ideas that led to modern conservation concepts in terms of long-term biodiversity conservation.

Number and distribution of large old ginkgos in east China: Implications for regional conservation

Large old ginkgos (LOGs), having important ecological, cultural and historical values, are widely distributed in China. However, little is known regarding their quantity and tree-habitat quality in the mesoscale distribution. Here, the quantity, spatial distribution and conservation status of Ginkgo biloba L. older than 100 years in Jiangsu Province, east China were examined using ArcGIS software and detrended correspondence analysis (DCA). Based on our collated data, Jiangsu Province included 2,123 LOG individuals and 237 LOG groves and both mostly occurred in southern and central Jiangsu. Most LOGs grew well and were distributed in villages, temples and government institutions. Ginkgos’ growth status was largely associated with tree-habitat types. LOGs performed worse in commercial areas, roadsides and residential districts than in other tree-habitat types. To protect these ginkgos, dynamic monitoring and strengthening of scientific management are required, especially for tree-habitats in the process of urban planning and construction. It is also necessary to improve the relationship between religious culture and conservation measures. This is the first study examining LOGs in Jiangsu Province using a unified standard and our findings provide a baseline for future studies and insights into the regional conservation of LOGs.

On the Management of Large-Diameter Trees in China’s Forests

Large-diameter trees have mainly been used for timber production in forestry practices. Recently, their critical roles played in biodiversity conservation and maintenance of ecosystem functions have been recognized. However, current forestry policy on the management of large-diameter trees is weak. As China is the biggest consumer of large-diameter timbers, how to maintain sustainable large-diameter timber resources as well as maximize ecological functions of the forests is a critical question to address. Here we summarize historical uses, distribution patterns, and management strategies of large-diameter trees in China. We found that large-diameter trees are mainly distributed in old-growth forests. Although China’s forest cover has increased rapidly in the past decades, large-diameter trees are rarely found in plantation forests and secondary forests. We suggest that knowledge of large-diameter trees should be widely disseminated in local forestry departments, especially their irreplaceable value in terms of biodiversity conservation and ecosystem functions. Protection of large-diameter trees, especially those in old-growth forests, is critical for sustainable forestry. To meet the increasing demand of large-diameter timbers, plantation forests and secondary forests should apply forest density management with thinning to cultivate more large-diameter trees.

Influence of monsoonal water-energy dynamics on terrestrial mollusk species-diversity gradients in northern China

Climate-related factors (e.g. environmental energy, water availability and climatic seasonality/variability) and habitat heterogeneity have long been considered as the main drivers of species diversity on a broad spatial scale. However, it is controversial whether the above environmental factors can explain observed diversity patterns in varied communities such as invertebrate taxonomic group, especially mollusks. Moreover, there are until now few systematic assessments of the relative roles of different factors in determining the patterns of mollusk species diversity in monsoon-dominated regions. Here, we depict variations in terrestrial mollusk diversity based on a dataset comprising 282 assemblages collected from surface soils along an ~800-km climatic gradient from subtropical to warm temperate and mid-temperate regions in northern China. The results show that mollusk species diversity increases significantly from ~3-4 species to ~17-19 species when annual temperature and precipitation increase up to ~12 °C and ~700 mm, respectively; however, at or above these values the rate of increase is reduced. These indicate that the relationships between mollusk species diversity and climatic factors are nonlinear. Statistical analysis suggests that water availability (relative humidity) and temperature seasonality (January temperature and annual temperature range) dominate the observed pattern of mollusk species diversity. Moreover, habitat factors such as vegetation condition and soil types were also important in determining mollusk species diversity. They may be an indirect reflection of the effects of monsoonal water-energy dynamic on mollusk communities. Our results suggest that more attention should be paid to water availability and temperature seasonality in predicting future biodiversity changes, especially in the environmentally stressed northwestern part of the East Asian monsoon region.