Subtropical Forest Community Research Articles

Variation in Niche and Interspecific Associations across Elevations in Subtropical Forest Communities of the Wuyi Mountains, Southeastern China

Variation in Niche and Interspecific Associations across Elevations in Subtropical Forest Communities of the Wuyi Mountains, Southeastern China

Low functional redundancy revealed high vulnerability of the subtropical evergreen broadleaved forests to environmental change

Anthropogenic-induced environmental changes threaten forest ecosystems by reducing their biodiversity and adaptive capacity. Understanding the sensitivity of ecosystem function to loss of diversity is vital in designing conservation strategies and maintaining the resilience of forest ecosystems in a changing world. Here, based on unique combinations of ten functional traits (termed as functional entities; FEs), we quantified the metrics of functional redundancy (FR) and functional vulnerability (FV) in 250 forest plots across five locations in subtropical evergreen broadleaved forests. We then examined the potential impacts of species loss on functional diversity in subtropical forest communities along environmental gradients (climate and soil). Results showed that the subtropical forests displayed a low level of functional redundancy (FR < 2). Over 75 % of the FEs in these subtropical forest communities were composed of only one species, with rare species emerging as pivotal contributors to these vulnerable FEs. The number of FEs and functional redundancy both increased with the rise in species richness, but functional vulnerability decreased with increasing species richness. Climatic factors, especially mean diurnal range, played crucial roles in determining the functions that the forest ecosystem delivers. Under variable temperature conditions, species in each plot were packed into a few FEs, leading to higher functional redundancy and lower functional vulnerability. These results highlighted that rare species contribute significantly to ecosystem functions and the highly diverse subtropical forest communities could show more insurance effects against species loss under stressful environmental conditions.

China's subtropical deciduous plants are more sensitive to climate change than evergreen plants by flowering phenology

AbstractThe ongoing climate change‐induced shifts in flowering phenology have emerged as a consequential force impacting biodiversity and ecosystems. Despite the globally recognized significance of flowering phenology as a key reproductive attribute, studies in subtropical regions have been relatively fewer, particularly in comparison to temperate and cold regions. Additionally, the nuanced response of deciduous and evergreen plants to climate change remains insufficiently explored. In addressing this gap, we built a phenological model and a generalized linear mixed effect model to assess the differential responses of key flowering phenological traits, that is, first flowering date (FFD), peak flowering date (PFD), end of flowering date (EFD), and flowering duration (FD), to climate factors (temperature and precipitation) between deciduous and evergreen plants. We observed distinct responses in flowering phenological traits to climate change between deciduous and evergreen plants. Specifically, the advancement of FFD, PFD, and EFD in deciduous in response to temperature rise exceeded that in evergreen plants. FD in evergreen plants exhibited a stronger extension to temperature increase compared to deciduous. Conversely, the phenological change of evergreen plants in response to decreasing precipitation was greater than that of deciduous ones. Since temperature is a decisive climatic factor in affecting phenological changes, climate change‐induced advances in flowering phenology of deciduous plants are still larger than evergreen plants. Projections from our phenological model under future climate scenarios (SSP 1‐2.6 and SSP 5‐8.5) indicate a continuous enlargement of difference in flowering phenology between deciduous and evergreen plants, with this trend escalating into the future (2100&gt;2070&gt;2050&gt;2030). The larger extension in FD of evergreens to climate change suggests a potential increase in their proportion within subtropical forest communities relative to deciduous plants. These insights contribute significantly to our understanding of the intricate dynamics of climate‐induced changes in subtropical plant ecosystems.

Altitude rather than season and slope aspect has the greatest effect on the bacterial communities in subtropical forests in Yunnan, China

Altitude rather than season and slope aspect has the greatest effect on the bacterial communities in subtropical forests in Yunnan, China

Soil bacterial communities are more sensitive to short-term nitrogen deposition than fungal communities in subtropical Chinese fir forests

The increasing rate of atmospheric nitrogen (N) deposition seriously affects the structure and function of ecosystems. Although soil microorganisms play a crucial role in ecosystem carbon (C) and nutrient cycling, the impact of N deposition on soil microbial communities in subtropical forest ecosystems is unclear. Here, we selected the subtropical Chinese fir (Cunninghamia lanceolata) forest as the research object and conducted simulated N deposition experiments with different levels of N deposition (0 kg N ha−1 yr−1,50 kg N ha−1 yr−1, 100 kg N ha−1 yr−1, and 200 kg N ha−1 yr−1, respectively) to explore the response of soil nutrients, soil microbial community structure, and potential ecological functions to short-term N deposition. We found that the bacterial richness Chao1 index and phylogenetic diversity PD_whole_tree decreased with the N deposition level approximately 13 % −16 % under MN and HN treatment. N deposition significantly altered the composition of soil bacterial communities (P < 0.05), but the responses of different taxa to N deposition were inconsistent at different stages of growing season. N deposition treatment significantly increased the relative abundance of Actinobacteria at both beginning of growing season (BGS) and end of growing season (EGS), decreased the relative abundances of Planctomycetes at BGS, and decreased the relative abundances of Elusimicrobia and Cyanobacteria at both BGS and EGS. Non-metric multidimensional scaling (NMDS) and Anosim (Analysis of similarities) analyses showed that the bacterial communities were clearly distinguished among treatments at both BGS and EGS. However, N deposition had a relatively small impact on fungal communities, only altering the fungal community structure at BGS. The impact of N deposition on soil microbial communities was mainly induced by the alteration in soil water content (SWC), pH, NO3–-N, and available nitrogen (AN). Both bacterial and fungal communities exhibit seasonal community dynamics, while the interaction of N deposition and season was mainly reflected in the impact on bacterial communities. Our research not only provides research ideas for the potential impact of nitrogen deposition on subtropical forest ecosystems in the short term, but also provides a theoretical basis for future scientific management and regulation of forestry, microorganisms, and sustainable management of Chinese fir plantations.

Climatic signals on phenological patterns among tree species in a subtropical forest community

The study of vegetative and reproductive phenophases of plants is critical for understanding aspects related to plant behavior in different environments. In the tropics, there is a gap of understanding related to plant phenology since the theoretical framework on the topic has been built from perspectives of the temperate region. Furthermore, there are few studies in tropical regions influenced by anthropic conditions, which may be important for understanding these issues in the face of future climate scenarios. This study aimed to describe the vegetative and reproductive phenology of trees in an urban subtropical forest community and to test the influence of climatic variables on the tree community. In an urban forest fragment in Rio Grande do Sul, Brazil, eight individuals of locally dominant species were monitored: Allophylus edulis, Casearia sylvestris, Guarea macrophylla, Mimosa bimucronata, Myrsine coriacea, Myrsine umbellata, Schinus glandulosum, and Schinus terebinthifolia. The monitoring occurred every two weeks, for two years, with the recording of the presence of leaf flushing, leaf shedding, flowering, and fruiting phenophases for each tree. The seasonality of the species was tested using the Rayleigh test. We described the common pattern of community phenological activity by a Principal Component Analysis. Finally, we correlated the common patterns of each phenophase in the community with climatic variables of total precipitation, average temperature, and day length. All species showed a non-uniform phenological pattern for the evaluated phenophases despite the variable intensity. We evidenced common patterns for the community only for the vegetative phenophases. The reproductive phenophases of flowering and fruiting present themselves independently among species in the community. Finally, we identified influences only of temperature and day length on the vegetative phenophases.

Potentially differential impacts on niche overlap between Chinese endangered Zelkova schneideriana and its associated tree species under climate change

Climate change has a significant impact on the potential distribution for endangered trees. However, to date, little is known about how the endangered trees and main associated ones in different types of subtropical forests respond to climate change. Here, we first selected the endangered Zelkova schneideriana endemic to China and its associated trees as focus species from two subtropical forest communities (i.e. deciduous broad-leaf forest, bamboo and broad-leaf mixed forest) in China, and divided them into two species pairs: Z. schneideriana vs. Celtis sinensis, and Z. schneideriana vs. Phyllostachys edulis. Then, we simulated the three species’ suitable areas under current and future climate scenarios using Maxent based on the occurrence records and environmental variables, and further measured niche overlap between each species pair over time. Our Maxent showed: (1) Temperature-related factors have greater influence on Z. schneideriana than the other factors. The most important factor influencing its population distribution was Min temperature of coldest month (Bio6), followed by Mean diurnal range (Bio2), with the total contribution of 78.9%. (2) Currently, the suitable area of Z. schneideriana was predicted to be 106.50 × 104 km2, mostly located in the subtropical region of China, especially in Anhui, Hubei, Hunan, Jiangsu, and Zhejiang provinces. (3) Its suitable area would decrease and its average migration distance was 19.72 km under 16 future climate scenarios, with the core distribution migrating northeast. (4) There is an asynchrony of potential niche overlap between species pairs. One species pair with C. sinensis will rise in terms of Schoener’s D and I values whereas the other one with P. edulis will decline in the future. This asynchrony can be ascribed to the different future suitable ranges of these focus species as well as their ecological characteristics. Our study provides a new perspective on the conservation for endangered trees and surrounding neighbors in Chinese subtropical forests.

Climate drivers of seed rain phenology of subtropical forest communities along an elevational gradient.

Seed rain phenology (the start and end date of seed rain) is an essential component of plant phenology, critical for understanding population regeneration and community dynamics. However, intra- and inter-annual changes of seed rain phenology along environmental gradients have rarely been studied and the responses of seed rain phenology to climate variations are unclear. We monitored seed rain phenology of four forest communities in four years at different elevations (900m, 1450m, 1650m, 1900m a.s.l.) of a subtropical mountain in Central China. We analyzed the spatiotemporal patterns of seed rain phenology of 29 common woody plant species (total observed species in the seed rain), and related the phenological variations to seed number and climatic variables using mixed-effect models with the correlation matrix of phylogeny. We found that changes in the period length were mainly driven by the end rather than the start date. The end date and the period length of seed rain were significantly different between the mast and non-mast seeding years, while no significant elevation-related trend was detected in seed rain phenology variation. Seed number, mean temperature in spring (Tspr), and winter (Twin), summer precipitation (Psum) had significant effects on seed rain phenology. When Tspr increased, the start date of seed rain advanced, while the end date was delayed and the seed rain period length was mainly prolonged by a higher seed number, Twin and Psum. Forest canopy might have a buffering effect on understory climatic conditions, especially in precipitation that lead to difference in seed rain phenology between canopy and shrub species. Our novel evidence of seed rain phenology can improve prediction of community regeneration dynamics in responding to climate changes.

Functional Diversity and Its Influencing Factors in a Subtropical Forest Community in China

Functional diversity is considered a key link between ecosystem functions and biodiversity, and forms the basis for making community diversity conservation strategies. Here, we chose a subtropical forest community in China as the research object, which is unique in that other regions of the world at the same latitude have almost no vegetation cover. We measured 17 functional traits of 100 plant species and calculated seven different functional diversity indices, based on functional richness, evenness, and divergence. We found that most functional diversity and species diversity indices significantly differed with plant habit. There was a significant positive correlation among functional richness indices. However, functional divergence indices, multidimensional functional divergence (FDiv), and Rao’s quadratic entropy index (RaoQ) were significantly negatively correlated, and RaoQ and functional divergence indices (FDis) were uncorrelated. The correlations between three types (richness, evenness, and divergence) of functional diversity indices and three species diversity indices were different. Lineage regression results generally showed that three functional richness indices (Average distance of functional traits (MFAD), Functional volume (FRic) and Posteriori functional group richness (FGR)) were increased with three species diversity indices (species richness (S), Shannon-Wiener index (H) and Pielou index (E)). The functional evenness index (FEve) decreased with species richness (S), Shannon-Wiener index (H) and increased with species evenness (Pielou index (E)), but the change trends were small. All three types of functional diversity indices declined with altitude, although altitude had a weak influence on them. Other environmental factors affected the functional diversity of the community. Here, soil total phosphorus (TP) was the most critical environmental factor and the convex had the least effect on functional diversity in our subtropical forest community. These results will contribute to our understanding of functional diversity in subtropical forests, and provide a basis for biodiversity conservation in this region.

Photoprotection Differences between Dominant Tree Species at Mid- and Late-Successional Stages in Subtropical Forests in Different Seasonal Environments.

Plants growing in subtropical regions are often affected by high temperature and high light in summer and low temperature and high light in winter. However, few studies have compared the photoprotection mechanism of tree species at different successional stages in these two environments, although such studies would be helpful in understanding the succession of forest communities in subtropical forests. In order to explore the strategies used by dominant species at different successional stages to cope with these two environmental conditions, we selected two dominant species in the mid-successional stage, Schima superba and Castanopsis chinensis, and two dominant species in the late-successional stage, Machilus chinensis and Cryptocarya chinensis. The cell membrane permeability, chlorophyll fluorescence, chlorophyll content, and a few light-protective substances of these dominant species were measured in summer and winter. The results show that in summer, the young leaves of dominant species in the mid-successional stage showed higher anthocyanin content and superoxide dismutase (SOD) activity, while those in the late-successional stage showed higher flavonoid and total phenolic content, total antioxidant activity, non-photochemical quenching (NPQ), and carotenoid/chlorophyll (Car/Chl) ratio. In winter, young leaves of dominant species in the mid-successional stage were superior to those in the late-successional stage only in terms of catalase (CAT) activity and NPQ, while the anthocyanin, flavonoids, and total phenol content, total antioxidant capacity, and Car/Chl ratio were significantly lower compared to the late-successional stage. Our results show that the dominant species in different successional stages adapted to environmental changes in different seasons through the alterations in their photoprotection strategies. In summer, the dominant species in the mid-successional stage mainly achieved photoprotection through light shielding and reactive-oxygen-species scavenging by SOD, while the antioxidant capacity of trees in the late-successional stage mainly came from an increased antioxidative compounds and heat dissipation. In winter, the dominant species in the mid-successional stage maintained their photoprotective ability mainly through the scavenging of reactive oxygen species by CAT and the heat dissipation provided by NPQ, while those in the late-successional stage were mainly protected by a combination of processes, including light shielding, heat dissipation, and antioxidant effects provided by enzymatic and non-enzymatic antioxidant systems. In conclusion, our study partially explains the mechanism of community succession in subtropical forests.

Leaf Venation Architecture in Relation to Leaf Size Across Leaf Habits and Vein Types in Subtropical Woody Plants.

Leaves are enormously diverse in their size and venation architecture, both of which are core determinants of plant adaptation to environments. Leaf size is an important determinant of leaf function and ecological strategy, while leaf venation, the main structure for support and transport, determines the growth, development, and performance of a leaf. The scaling relationship between venation architecture and leaf size has been explored, but the relationship within a community and its potential variations among species with different vein types and leaf habits have not been investigated. Here, we measured vein traits and leaf size across 39 broad-leaved woody species within a subtropical forest community in China and analyzed the scaling relationship using ordinary least squares and standard major axis method. Then, we compared our results with the global dataset. The major vein density, and the ratio of major (1° and 2°) to minor (3° and higher) vein density both geometrically declined with leaf size across different vein types and leaf habits. Further, palmate-veined species have higher major vein density and a higher ratio of major to minor vein density at the given leaf size than pinnate-veined species, while evergreen and deciduous species showed no difference. These robust trends were confirmed by reanalyzing the global dataset using the same major vein classification as ours. We also found a tradeoff between the cell wall mass per vein length of the major vein and the major vein density. These vein scaling relationships have important implications on the optimization of leaf size, niche differentiation of coexisting species, plant drought tolerance, and species distribution.

亚热带不同纬度森林群落物种空间分布格局

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带不同纬度森林群落物种空间分布格局 DOI: 10.5846/stxb202106121570 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32060305）；广西自然科学基金面上项目（2020GXNSFAA159108，2022GXNSFAA035583） Spatial distribution patterns of forest community species at different latitudes in the subtropics Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨我国亚热带森林群落中物种空间分布格局特点及其成因，揭示其共性规律和个性差异，为相关区域的生物多样性保护和监测工作提供科学依据。选取我国亚热带不同纬度的6个1 hm2典型森林群落中所有胸径（DBH，Diameter at Breast Height）≥ 1 cm的物种为研究对象；采用L （t）方程统计所有监测物种的空间分布格局类型，为满足L （t）方程的统计精度，将各群落中多度≥10株的植物以物种为单位统计，多度<10株的低多度物种和单个体物种则以种组为单位进行空间点格局分析；并对物种多度、胸径与空间聚集程度的度量指标L10进行相关性分析。结果表明：（1）亚热带不同纬度群落中多度≥10株物种的空间分布格局表现出相似的尺度依赖性规律：显著聚集分布比例随尺度增大而降低，不同纬度群落的变化幅度存在差异，纬度较低的群落稳定性更强。（2）各群落中低多度种组空间分布格局表现出小尺度显著聚集分布，大尺度随机分布的尺度效应，但尺度效应在不同纬度群落间存在差异；各群落的单个体种组空间分布格局均以随机分布为主。（3）不同纬度群落物种多度与空间聚集程度之间均存在负相关关系，物种多度对空间聚集程度的影响随纬度从高到低逐渐减弱。（4）较高纬度群落物种胸径与空间聚集程度之间存在负相关关系；随纬度从高到低，物种胸径对空间聚集程度影响水平逐渐降低。对亚热带不同纬度森林群落物种空间分布格局形成原因的进一步探讨，认为由纬度差异引起的生境异质性是影响群落物种空间分布格局产生过程的主要因素，此外，林型、扩散限制、密度制约和随机作用是影响各群落物种空间格局成因及多样性维持的次要因素。 Abstract:This study was conducted to investigate the characteristics of species spatial distribution patterns and their causes in subtropical forest communities in China. It also revealed the common patterns and individual differences in the spatial distribution patterns of species in different forest communities in the subtropics. The purpose of the study was to provide a scientific basis for biodiversity conservation and monitoring in the relevant regions. All species with diameter at breast height (DBH) ≥ 1 cm in six typical forest communities of 1 hm2 at different latitudes in subtropical China were selected for the study. The L(t) function was used to count the spatial distribution pattern types of all the monitored species. In order to meet the statistical precision of the L(t) function, the plants with abundance ≥ 10 plants in each community were counted as species, and low abundance species with abundance < 10 plants and single individual species were analyzed as species groups for spatial point pattern analysis; and the correlation between species abundance, DBH and the metric of spatial aggregation degree, L10, was analyzed. The results showed that:(1) The spatial distribution patterns of species with abundance ≥ 10 plants in communities at different latitudes in the subtropics showed similar scale-dependent patterns:the proportion of significantly aggregated distributions decreased with increasing scale, the magnitude of change in communities at different latitudes differed, and communities at lower latitudes were more stable. (2) The spatial distribution pattern of low abundance species groups in each community showed the scale effect of small-scale significantly aggregated distribution and large-scale random distribution, but the scale effect differed among communities at different latitudes; the spatial distribution pattern of individual species groups in each community was mainly random distribution. (3) There was a negative correlation between species abundance and spatial aggregation in communities at different latitudes, and the effect of species abundance on spatial aggregation diminished with latitude from high to low. (4) There was a negative correlation between DBH and the degree of spatial aggregation in communities at higher latitudes; the level of influence of DBH on the degree of spatial aggregation gradually decreased with higher to lower latitudes. The spatial distribution patterns of species in forest communities at different latitudes in the subtropics were further explored. It was concluded that habitat heterogeneity caused by latitudinal differences was the main factor influencing the process of spatial distribution patterns of community species, while forest type, dispersal limitation, density constraint and stochastic effects were secondary factors affecting the causes of spatial patterns of species and maintenance of diversity in each community. 参考文献 相似文献 引证文献

Nature restoration shifts the abundance and structure of soil nematode communities in subtropical forests

Nature restoration shifts the abundance and structure of soil nematode communities in subtropical forests

Interpretation of the difference in shade tolerance of two subtropical forest tree species of different successional stages at the transcriptome and physiological levels.

Differences in plant shade tolerance constitute a major mechanism driving the succession of forest communities in subtropical forests. However, the indirect effects of differences in light requirements on the growth of mid- and late-successional tree species are unclear, and this potential growth effect has not been explained at the transcriptome level. Here, a typical mid-successional dominant tree species, Schima superba Gardn. et Champ, and a typical late-successional dominant tree species, Cryptocarya concinna Hance were used as materials and planted under 100% full light (FL) and 30% FL (low light, LL) to explore the responses of tree species in different successional stages of subtropical forests to different light environments. Transcriptome sequencing was used to analyze the expression changes in genes related to growth and photoprotection under different light environments. The young leaves of S. superba accumulated more malondialdehyde (MDA) and superoxide radicals (${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$) under LL. A lower hormone content (auxin, cytokinin, gibberellin) in the young leaves, a weaker photosynthetic capacity in the mature leaves and significant downregulation of related gene expression were also found under LL, which resulted in the total biomass of S. superba under LL being lower than that under FL. The young leaves of C. concinna had less MDA and ${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$, and a higher hormone contents under LL than those under FL. There was no significant difference in photosynthetic capacity between mature leaves in contrasting light environments. Although the biomass of C. concinna under LL was less than that under FL, the height of C. concinna under LL was higher than that under FL, indicating that C. concinna could grow well under the two light environments. Our results describing the acclimatization of light at the physiological, molecular and transcriptome levels are important for a complete understanding of successional mechanisms.

Phylogenetic relatedness of woody angiosperm assemblages and its environmental determinants along a subtropical elevational gradient in China

The species composition of plant communities is determined by a number of factors, including current environmental conditions as well as biogeographical and evolutionary history. Despite evidence that plant diversity decreases and species relatedness increases along latitudinal and environmental gradients (e.g., low temperatures), it remains unclear whether these same patterns occur along elevational gradients, especially in the subtropical mountainous areas harboring rich biodiversity. In this study, we explored the pattern of phylogenetic relatedness of woody angiosperm assemblages and examined the effects of temperature variables on the phylogenetic relatedness among angiosperm woody plants using generalized linear model in subtropical forest communities along a broad elevational gradient in the Dulong Valley of Yunnan Province, China. Our results showed that woody angiosperm species in local forest plots tend to be more phylogenetically related at higher elevations and in areas with lower temperatures. Additionally, winter average temperature, rather than mean annual temperature, is a major predictor of the pattern of increasing phylogenetic relatedness with increasing elevation. This finding is consistent with the prediction of ‘Tropical Niche Conservatism’ hypothesis, which highlights the role of niche constraints in driving phylogenetic community assembly along an elevational gradient.

珍稀濒危树种陆均松天然种群结构与空间分布格局

PDF HTML阅读 XML下载 导出引用 引用提醒 珍稀濒危树种陆均松天然种群结构与空间分布格局 DOI: 10.5846/stxb201905090948 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项资金（CAFBB2017ZB004） Natural population structure and spatial distribution pattern of rare and endangered species Dacrydium pectinatum Author: Affiliation: Fund Project: Study on the Monitoring and Exhaustion Mechanism of Dacrydium Pierrei Resources 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究陆均松（Dacrydium pectinatum）种群生存现状及分布格局，对BWL、DLS、JFL 三种不同分布区域的陆均松天然种群进行了调查，分析了其天然群落乔木层物种多样性及优势种组成、龄级结构及分布格局三个方面的空间异质性，结果表明：（1）三种陆均松天然群落乔木层物种丰富度及多样性指数均较高，基本表现为BWL>JFL>DLS，且远高于中高纬度温带及亚热带森林群落；群落内多为小密度种群，少有占绝对优势地位的树种，符合热带山地雨林物种组成的一般规律。（2）龄级结构有所差异，BWL和JFL种群呈衰退趋势，共同特点是幼年树数量较少，成年和老年树比例较高；DLS种群幼年树数量在所有个体中比例最高，属于增长型种群。（3）BWL和DLS种群整体呈聚集分布，幼年至老年阶段由聚集分布转变为均匀分布，JFL种群整体及不同发育阶段均呈均匀分布状态；聚集强度表现为DLS > BWL > JFL，幼年树 > 成年树 > 老年树。陆均松是热带山地雨林的关键种和建群种，对研究海南热带雨林的起源及其区系特征具有重要意义，针对其生存现状，可根据实际情况，利用人工辅助措施如开辟林窗、合理疏伐等方式进行保护及更新复壮。 Abstract:In order to study the survival status and distribution pattern of Dacrydium pectinatum population, we investigated three different distribution areas, namely BWL, DLS, and JFL in Hainan Island. The spatial heterogeneity in three aspects of the species diversity and dominant species composition of the natural community arbor layer, age structure, and distribution pattern was analyzed. The results showed that (1) the arbor layer species abundance and diversity index of the three D. pectinatum natural community were higher as a whole, which followed the order of BWL > JFL > DLS, and much higher than those of the mid-high latitude temperate zone and subtropical forest community. The populations in the community were mostly small-density populations, and there were few absolutely dominant species, which is consistent with the general rule of species composition of tropical mountain rainforests. (2) The age structure of these three populations had its own characteristics. BWL and JFL showed a recession trend. The common feature was that the number of Juvenile tree was small, and the proportion of adult trees and elderly trees was high. The number of Juvenile tree in DLS was the most for all individuals and belonged to the growth population. (3) The overall state of the D. pectinatum population of BWL and JFL was aggregate clustered distribution. The juvenile tree stage was also a clustered distribution, but in the elderly tree stage, it changed from clustered distribution to uniform distribution. The JFL D. pectinatum population showed a uniform distribution throughout all individuals and different developmental stages. Their aggregation intensity was expressed as DLS > BWL > JFL and juvenile > adult > elderly. D. pectinatum is a key species of tropical mountain rainforests, which is of great significance for studying the origin and flora characteristics of Hainan tropical rainforest. For its current survival status, we can use manual auxiliary measures such as opening forest windows and rational thinning to protect and rejuvenate D. pectinatum population based on the actual situation. 参考文献 相似文献 引证文献

Evidence for trait‐based community assembly patterns in hardwood hammock forests

AbstractThe hardwood forests of south Florida, commonly referred to as hammocks, persist as well‐drained patches of broadleaf forest, embedded in a matrix of brackish water swamp, freshwater marsh, or pineland. Little is known about the patterns of community assembly of these subtropical forest communities in the landscape mosaic of south Florida. We used a functional trait approach to understand the composition of these communities and their responses to environmental variation across four areas of south Florida: the pine rocklands and freshwater marshes in Everglades National Park, and the lower and upper Florida Keys, where the hammocks are surrounded by halophytic swamp communities. These sites represent an environmental gradient from less‐productive, more xeric sites in the lower Florida Keys, to more‐productive, wetter sites in the Everglades marshes. We examined the patterns of trait variation at three levels (individual, population, and community) to examine the underlying processes driving assembly in these hammock communities. To understand processes governing community composition in each site, we used methods that partition variance in six traits (maximum tree height, specific leaf area, wood specific gravity, leaf nitrogen, leaf phosphorus, and leaf stable carbon isotope ratios) into internal and external filtering components. Community‐weighted mean trait values for three traits (specific leaf area, height, and leaf phosphorus) increased significantly from dry, less‐productive coastal sites in the Florida Keys to the moist, more‐productive areas on the mainland, while wood specific gravity and leaf δ13C showed the opposite pattern. For one or more traits per site, standardized effect sizes differed significantly from null expectation. Processes such as competition for resources (e.g., water, nutrients, light) and species sorting across microhabitats (i.e., within site) operate to increase local functional trait variation within communities and among species across sites. External filtering on individuals for height and leaf phosphorus differed significantly from null expectations across sites, while external filtering on species was only observed for specific leaf area, maximum tree height, and leaf phosphorus. These results are consistent with strong environmental filtering across the region, among local communities differing in freshwater accessibility or that occupy different positions along strong edaphic gradients. Our results confirm the importance of intraspecific variation among species and reflect a high degree of trait plasticity across the environmental gradient.

Effects of canopy and understory nitrogen addition on the structure and eco-exergy of a subtropical forest community

Abstract The health of plant communities has been severely threatened by nitrogen (N) deposition across all types of ecosystems. The effect of N deposition on the structure of forest communities (as measured by the Shannon Wiener index, evenness, richness, density and biomass) has been investigated extensively, mostly through understory N-addition experiments, which has been criticized for neglecting the function of the canopy in interception, up-take and transformation of N, as well as other elements. To clarify this problem, the effects of canopy and understory N-addition on subtropical evergreen forest community structure were quantified and compared in this study. Furthermore, a bio-thermodynamic measurement, eco-exergy, was applied as a complement to the classic community structure index system to evaluate the health status of forest communities by bringing the genetic information embodied in each species into consideration. The results showed that compared to understory N-addition, richness in the shrub layer was more sensitive to the canopy N-addition. Thus, studies that only consider the effects of N-addition to the understory may underestimate the effects of N-addition on forest communities, as a whole. In this study, even though N-addition to the understory did not alter the forest structure indices (Shannon Wiener index, evenness, richness, density and biomass), significantly, it did decrease the specific eco-exergy of the subtropical, evergreen, forest community, as observed for N-addition to the canopy. The decrease was mainly contributed by the decline in the fraction of higher plants and an increase in the fraction of lower plants within the tree and herb layers. Thus, our results demonstrated that the health status of the subtropical, evergreen, forest community as determined by thermodynamic measures was more sensitive to N-addition compared to the classic community indices mentioned above, and the community structures in both tree and herb layers were also sensitive to N-addition, besides the shrub layer.

Tree species identity surpasses richness in affecting soil microbial richness and community composition in subtropical forests

Plant interactions and feedbacks with soil microorganisms play an important role in sustaining the functions and stability of terrestrial ecosystems, yet the effects of tree species diversity on soil microbial community in forest ecosystems are still not well understood. Here, we examined the effects of tree species richness (1–12 species) and the presence of certain influential tree species (sampling effect) on soil bacterial and fungal communities in Chinese subtropical forests, using high-throughput Illumina sequencing for microbial identification. We observed that beta rather than alpha diversities of tree species and soil microorganisms were strong coupled. Multivariate regression and redundancy analyses revealed that the effects of tree species identity dominated over tree species richness on the diversity and composition of bacterial and fungal communities in both organic and top mineral soil horizons. Soil pH, nutrients and topography were always identified as significant predictors in the best multivariate models. Tree species have stronger effect on fungi than bacteria in organic soil, and on ectomycorrhizal fungi than saprotrophic fungi in mineral topsoil. Concluding, tree species identity, along with abiotic soil and topographical conditions, were more important factors determining the soil microbial communities in subtropical forests than tree diversity per se.

Changes in taxonomic and phylogenetic dissimilarity among four subtropical forest communities during 30 years of restoration

Enhancement and conservation of biodiversity in recovering communities is one of the primary goals of forest ecology and restoration. To achieve a better understanding of the mechanisms underlying community assembly during restoration, we examined changes in taxonomic and phylogenetic dissimilarity in four types of subtropical forests, consisting of a Eucalyptus plantation (EE), an Acacia mangium plantation (AM), a mixed native species plantation (NS), and a mixed coniferous plantation (MC), over 30 years of restoration (1985–2015). Temporal variation in taxonomic and phylogenetic dissimilarity patterns were found to differ among the four plantation types, although their taxonomic diversity (species richness) and phylogenetic diversity (PD) increased monotonically as succession proceeded. Community dissimilarity decreased nonlinearly over the 30 years, and species composition within each plantation tended to stabilize at around 20 years. Overall, the phylogenetic structure of each plantation was random during the succession period. Taxonomic and phylogenetic rates did not vary markedly along the 30 years of restoration, but the taxonomic turnover rate of MC increased significantly while the phylogenetic turnover rate of NC augmented remarkably. These results indicated that deterministic processes played a more important role in determining the temporal dynamics of community composition while stochastic processes were more important for phylogenetic structure. Our findings further inform the development and design of appropriate restoration strategies, and provide insights into understanding the mechanisms regulating community assembly during the process of forest restoration.