Aims Although shrubs are an important component of forests,their role has not yet been considered in forest biodiversity experiments.In the biodiversity-ecosystem functioning(BEF)experiment with subtropical tree speci...Aims Although shrubs are an important component of forests,their role has not yet been considered in forest biodiversity experiments.In the biodiversity-ecosystem functioning(BEF)experiment with subtropical tree species in south-east China(BEF-China),we factorially combined tree with shrub species-diversity treatments.Here,we tested the hypotheses that shrub survival differs between the 10 planted shrub species,with lower survival rates of late-than early-successional species and is affected by environmental conditions,such as topography and top soil characteristics,as well as by biotic factors,represented by tree,shrub and herb layer characteristics.Methods We analyzed the survival of 42000 shrub individuals in 105 plots varying in tree and shrub species richness of the BEF-China project four years after planting.Shrub survival was analyzed with generalized linear mixed effects models at the level of individuals and with variance partitioning at the plot level.Random intercept and random slope models of different explanatory variables were compared with respect to the Bayesian Information Criterion(BIC).Important Findings Survival rates differed largely between the 10 shrub species,ranging from 26%to 91%for Ardisia crenata and Distylium buxifolium,respectively.Irrespective of species identity,single abiotic factors explained up to 5%of species survival,with a negative effect of altitude and slope inclination and a positive effect of the topsoil carbon to nitrogen ratio,which pointed to drought as the major cause of shrub mortality.In contrast,neither tree nor shrub richness affected shrub survival at this early stage of the experiment.Among the biotic predictors,only herb layer species richness and cover of the dominant fern species(Dicranopteris pedata)affected shrub survival.Overall,our models that included all variables could explain about 65%in shrub survival,with environmental variables being most influential,followed by shrub species identity,while tree species diversity(species richness and identity)and herb layer characteristics contributed much less.Thus,in this early stage of the experiment the biotic interactions among shrubs and between shrubs and trees have not yet overruled the impact of abiotic environmental factors.展开更多
Ecological assembly rules in evergreen broad-leaved forest are far from clear understanding.Spatial dispersion of individuals in a species is central in ecological theory.We analyzed the spatial patterns as well as as...Ecological assembly rules in evergreen broad-leaved forest are far from clear understanding.Spatial dispersion of individuals in a species is central in ecological theory.We analyzed the spatial patterns as well as associations between adult and juvenile of each tree species in a 5-ha subtropical evergreen broad-leaved forest plot in eastern China.Out of the 74 species occurring with more than 10 individuals,88.4%of these species are aggregated.Most of them are aggregated from small to large scales.Spatial distributions of some species corre-spond with topography.Many bad dispersed species in the Baishanzu exhibit a highly aggregated distribution at small scales.These suggest that environmental heterogeneity and/or dispersal limitation may be the most important mechanisms that control the distribution patterns of these species.Our observations of the aggregations of abundant species basically support the hypothesis that dispersal limitation decreases as the number of reproductive trees increases.The rest species are randomly distributed,with less than 10 individuals.For most common species,spatial aggregation is weaker in larger diameter classes,and the distance between adults is larger than that between juveniles and adults,suggesting that density-dependence works on loosing aggregation and excluding conspecific juveniles away from adult trees.However,the density-dependent effect is not strong enough to eliminate all seedlings near adult trees and to result in a regular distribution of trees;thus the density dependence is usually masked by the refuge effect.展开更多
基金financed by the German Research Foundation(DFG FOR 891/1,2,3)in a grant to H.B.(Br1698/10-3)the Sino-German Centre for Research Promotion in Beijing for travel grants and the participation in a summer school on scientific writing(GZ 785)support through the cooperation group“Linkages between plant diversity,microbial diversity and ecosystem functioning in subtropical forest”(GZ 986).
文摘Aims Although shrubs are an important component of forests,their role has not yet been considered in forest biodiversity experiments.In the biodiversity-ecosystem functioning(BEF)experiment with subtropical tree species in south-east China(BEF-China),we factorially combined tree with shrub species-diversity treatments.Here,we tested the hypotheses that shrub survival differs between the 10 planted shrub species,with lower survival rates of late-than early-successional species and is affected by environmental conditions,such as topography and top soil characteristics,as well as by biotic factors,represented by tree,shrub and herb layer characteristics.Methods We analyzed the survival of 42000 shrub individuals in 105 plots varying in tree and shrub species richness of the BEF-China project four years after planting.Shrub survival was analyzed with generalized linear mixed effects models at the level of individuals and with variance partitioning at the plot level.Random intercept and random slope models of different explanatory variables were compared with respect to the Bayesian Information Criterion(BIC).Important Findings Survival rates differed largely between the 10 shrub species,ranging from 26%to 91%for Ardisia crenata and Distylium buxifolium,respectively.Irrespective of species identity,single abiotic factors explained up to 5%of species survival,with a negative effect of altitude and slope inclination and a positive effect of the topsoil carbon to nitrogen ratio,which pointed to drought as the major cause of shrub mortality.In contrast,neither tree nor shrub richness affected shrub survival at this early stage of the experiment.Among the biotic predictors,only herb layer species richness and cover of the dominant fern species(Dicranopteris pedata)affected shrub survival.Overall,our models that included all variables could explain about 65%in shrub survival,with environmental variables being most influential,followed by shrub species identity,while tree species diversity(species richness and identity)and herb layer characteristics contributed much less.Thus,in this early stage of the experiment the biotic interactions among shrubs and between shrubs and trees have not yet overruled the impact of abiotic environmental factors.
文摘Ecological assembly rules in evergreen broad-leaved forest are far from clear understanding.Spatial dispersion of individuals in a species is central in ecological theory.We analyzed the spatial patterns as well as associations between adult and juvenile of each tree species in a 5-ha subtropical evergreen broad-leaved forest plot in eastern China.Out of the 74 species occurring with more than 10 individuals,88.4%of these species are aggregated.Most of them are aggregated from small to large scales.Spatial distributions of some species corre-spond with topography.Many bad dispersed species in the Baishanzu exhibit a highly aggregated distribution at small scales.These suggest that environmental heterogeneity and/or dispersal limitation may be the most important mechanisms that control the distribution patterns of these species.Our observations of the aggregations of abundant species basically support the hypothesis that dispersal limitation decreases as the number of reproductive trees increases.The rest species are randomly distributed,with less than 10 individuals.For most common species,spatial aggregation is weaker in larger diameter classes,and the distance between adults is larger than that between juveniles and adults,suggesting that density-dependence works on loosing aggregation and excluding conspecific juveniles away from adult trees.However,the density-dependent effect is not strong enough to eliminate all seedlings near adult trees and to result in a regular distribution of trees;thus the density dependence is usually masked by the refuge effect.