中国中亚热带常绿阔叶林群落木本植物多样性比较

常绿阔叶林是我国亚热带的地带性植被类型,也是我国最重要的植被类型之一。常绿阔叶林植被型下各种群落类型的物种组成、结构、动态等特征已有大量研究,本研究基于浙江的天童和古田山、湖南的八大公山以及云南的珠江源、雕翎山和鸡足山6个大型常绿阔叶林动态监测样地的调查数据,对其木本植物的物种组成、区系成分、生长型类型百分比、种–面积关系进行了综合比较,以期进一步了解中国中亚热带常绿阔叶林在东、中、西部地区的物种多样性差异。结果显示:(1)中国中亚热带中部的八大公山样地物种的科、属、种丰富度最高,其次为东部的天童和古田山样地,而西部的珠江源、雕翎山和鸡足山样地的丰富度最低,相同植被类型样地的物种组成相似性最高,东、中、西部的常绿阔叶林植被的物种组成存在显著的差异;(2)东部样地木本植物的科、属均以热带区系为主,尤其泛热带分布的科、属最多,而中、西部样地虽然以热带科为主,但以温带属居多,北温带分布属最多;(3)东、中部3个样地木本植物以乔木成分为主,天童、古田山和八大公山样地乔木种比例分别是57.4%、51.6%和55.9%,西部样地灌木(珠江源、雕翎山和鸡足山样地分别是56.9%、54.2%、48.5%)成分均高于乔木(43.1%、41.7%、42.7%),中部样地木本植物落叶种(59.2%)占比远高于常绿种(40.8%),东、西部样地则是常绿种比例高于落叶种,天童、古田山、珠江源、雕翎山、鸡足山样地常绿种比例分别是51.3%、59.1%、62.7%、69.8%、58.3%;(4)八大公山和雕翎山样地的常绿种(分别有97种和67种)和落叶种(141种,29种)在数量上差距最大,雕翎山和珠江源样地的常绿种(69.8%,62.7%)和落叶种(30.2%,37.3%)在比例上差距最大。上述研究结果反映了中国中亚热带典型常绿阔叶林、山地常绿落叶阔叶混交林、半湿润常绿阔叶林的群落物种组成、物种多样性和群落结构的差异,为指示中亚热带常绿阔叶林植被从东到西的物种周转特征和植被变化规律提供了科学依据。

Disentangling the effects of topography and space on the distributions of dominant species in a subtropical forest

Topography and space are two important factors determining plant species assemblages in forest communities.Quantification of the contribution of these two factors in determining species distribution helps us to evaluate their relative importance in determining species assemblages.This study aims to disentangle the effect of topography and space on the distributions of 14 dominant species in a subtropical mixed forest.Spearman correlation analysis and the torustranslation test were used to test the species–habitat associations.Variation partitioning was used to quantify the relative contributions of topography and space at three sampling scales and three life stages.Correlation analyses and torus-translation tests showed species abundance was mostly correlated with topographic wetness index,vertical distance from the channel network and convexity.Variation partitioning showed that pure topography,pure space and spatially structured topography explained about 2.1 %,41.2 % and 13.8 %of the variation in species distributions,respectively.For nine species,total topography fractions peaked in 20 m quadrats.For ten species,the pure space fractions peaked in 50 m quadrats.For many species,the total topography fraction andthe pure space fraction were larger for the most abundant life stages,which reflected the importance of sampling effect.However,some cases did not follow this trend suggesting that the effects of ecological processes such as habitat filtering,density dependence or dispersal limitation may exceed the sampling effects.In conclusion,we found that spatially structured topography and pure space primarily shaped the distribution of dominant tree species.Furthermore,their effects were both scale- and life stage-dependent.

Density dependence and habitat preference shape seedling survival in a subtropical forest in central China

Aims seedlings are vulnerable to many kinds of fatal abiotic and biotic agents,and examining the causes of seedling dynamics can help understand mechanisms of species coexistence.To disentangle the relative importance of neighborhood densities,habitat factors and phylogenetic relatedness on focal seedling survival,we monitored the survival of 5306 seedlings of 104 species>15 months.We address the following questions:(i)How do neighborhood densities,habitat variables and phylogenetic relatedness affect seedling survival?What is the relative importance of conspecific densities,habitat variables and phylogenetic relatedness to seedling survival?(ii)Does the importance of the neighborhood densities,habitat variables and phylogenetic relatedness vary among growth forms,leaf habits or dispersal modes?specially,does the conspecific negative density dependence inhibit tree and decidu-ous seedlings more compared with shrub and evergreen species?Does density dependence affect the wind and animal-dispersed species equally?Methods We established 135 census stations to monitor seedling dynamics in a 25-ha subtropical forest plot in central China.Conspecific and heterospecific seedling density in the 1-m2 seedling plot and adult basal area within a 20-m radius provided neighborhood density var-iables.mean elevation,convexity and aspect of every 5-×5-m grid with seedling plots were used to quantify habitat characteristics.We calculated the relative average phylodiversity between focal seed-ling and heterospecific neighbors to quantify the species related-ness in the neighborhood.Eight candidate generalized linear mixed models with binominal error distribution were used to compare the relative importance of these variables to seedling survival.akaike’s information criteria were used to identify the most parsimonious models.Important Findingsat the community level,both the neighborhood densities and phylogenetic relatedness were important to seedling survival.We found negative effects of increasing conspecific seedlings,which suggested the existence of species-specific density-dependent mortality.Phylodiversity of heterospecific neighbors was negatively related to survival of focal seedlings,indicating similar habitat preference shared among phylogenetically closely related species may drive seedling survival.The relative importance of neighborhood densities,habitat variables and phylogenetic relatedness varied among ecological guilds.Conspecific densities had significant negative effect for deciduous and wind-dispersed species,and marginally significant for tree seedlings>10 cm tall and animal-dispersed species.Habitat variables had limited effects on seedling survival,and only elevation was related to the sur-vival of evergreen species in the best-fit model.We conclude that both negative density-dependent mortality and habitat preference reflected by the phylogenetic relatedness shape the species coex-istence at seedling stage in this forest.

中国植被图(1:1000000)现实性更新

植被图是生物多样性保护、生态学研究、植被管理与恢复和国家决策的重要辅助信息源.我国上一代植被图,即中国植被图(1:1000000),是由逾250位生态学家组成的团队自20世纪80年代花了20多年完成的.但是,随着过去30多年间的快速发展,我国的植被分布与植被类型发生了剧烈的变化,对上一代植被图进行现实性更新已成为迫在眉睫的需求.本文使用了一种"众源采集-变化检测-遥感分类-专家审核"的策略尝试对中国植被图(1:1000000)进行现实性更新.本研究共收集了203024条地面调查数据,并有50余位植被生态学家参与到专家审核的工作中.更新后的植被图包含12个植被型组、55个植被(亚)型和866个(亚)群系类别,精度在植被型组、植被(亚)型和(亚)群系水平上分别为64.8%,61%和40%.与上一代植被图相比,过去30多年间的人类活动和气候变化导致了我国约330万km^2植被类型发生了变化.更新后的植被图将会有助于理解和管理我国的陆地生态系统.

Effects of topography on structuring species assemblages in a subtropical forest

Aims Topography has long been recognized as an important factor in shaping species distributions.Many studies revealed that species may show species-habitat associations.However,few studies inves-tigate how species assemblages are associated with local habitats,and it still remains unclear how the community-habitat associa-tions vary with species abundance class and life stage.In this study,we analyzed the community-habitat associations in a subtropical montane forest.Methods The fully mapped 25-ha(500×500 m)forest plot is located in Badagongshan Nature Reserve in Hunan Province,Central China.It was divided into 625(20×20 m)quadrats.Habitat types were classified by multivariate regression tree analyses that cluster areas with similar species composition according to the topographic characteristics.Indicator species analysis was used to identify the most important species for structuring species assemblages.We also compared the community-habitat associations for two levels of species abundances(i.e.abundant and rare)and three different life stages(i.e.saplings,juveniles and adults),while accounting for sample size effects.Important Findings The Badagongshan plot was divided into five distinct habitat types,which explained 34.7%of the variance in tree species composi-tion.Even with sample size taken into account,community-habi-tat associations for rare species were much weaker than those for abundant species.Also when accounting for sample size,very small differences were found in the variance explained by topography for the three life stages.Indicator species of habitat types were mainly abundant species,and nearly all adult stage indicator species were also indicators in juvenile and sapling stages.Our study manifested that topographical habitat filtering was important in shaping over-all local species compositions.However,habitat filtering was not important in shaping rare species’distributions in this forest.The community-habitat association patterns in this forest were mainly shaped by abundant species.In addition,during the transitions from saplings to juveniles,and from juveniles to adults,the relative importance of habitat filtering was very weak.

Pattern and drivers of species- genetic diversity correlation in natural forest tree communities across a biodiversity hotspot

Aims Exploring species-genetic diversity correlation(SGDC)is essential for understanding spatial patterns of diversity and the underlying mechanisms.Until now,latitudinal patterns of species diversity(SD)and genetic diversity(GD)were rarely studied simultaneously.As the freezing-tolerance hypothesis predicts a decrease of SD from low to high latitudes and the central-marginal hypothesis predicts a unimodal pattern of GD along latitude,we hypothesized that SD and GD are uncorrelated.We also tested how climatic and edaphic factors affect the correlation between the two levels of biodiversity.Methods We measured(i)SD(species richness and Simpson’s diversity index)and community dissimilarity of woody plants(63 plots),(ii)GD(al-lelic richness and expected heterozygosity)and genetic differen-tiation of a dominant tree species(Euptelea pleiospermum;678 individuals from 21 populations)using nuclear microsatellite data,and(iii)climatic(annual mean precipitation,annual mean tempera-ture,minimum temperature,maximum temperature,annual rela-tive moisture,solar radiation,photosynthetically active radiation)and edaphic(total C,total N,total P,available P,K,Ca,Mg,Al,Fe,Mn,Ni,Zn,B,Mo,Cu,pH)variables of 21 sites.We conducted both linear and quadratic regression analyses of diversity param-eters against latitude.Relationships between SD and GD were tested using Pearson’s correlation.Pearson’s and Spearman’sρcor-relation coefficients were calculated between diversity parameters and environmental variables.We used stepwise multiple regression analysis to identify the significant environmental predictors of SD and GD.Important Findings We observed no significant correlation between measures of SD and GD.SD decreases with increasing latitude,which can be partly explained by the freezing-tolerance hypothesis,whereas GD pre-sents a unimodal pattern along the latitudinal gradient,which is consistent with the prediction of the central-marginal hypothesis.The contrasting latitudinal patterns of SD and GD indicate that the two levels of biodiversity do not co-vary in space.Based on both correlation analysis and stepwise multiple regression analysis,SD is only related to climatic variables,whereas GD is mainly related to edaphic variables.Our results show that different geographical and environmental factors affect SD and GD,driving the non-significant correlation between the two fundamental levels of biodiversity.Furthermore,a significantly positive correlation was observed be-tween genetic distance and community dissimilarity,both of which were significantly correlated with geographical distance.