Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring fo...Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring formation to clarify the radial growth of trees. Tree-ring width standard chronology(STD) was established using samples of Larix principis-rupprechtii collected at 2303 m altitude on Luya Mountain. Using the Vaganov-Shashkin(VS) model to simulate growth and development, the internal physiological mechanism of radial growth is identified. It was concluded that:(1) the growing season of L. principis-rupprechtii was May to September;(2) soil moisture was a significant factor in the early and late growing seasons, and temperature was the dominant factor in its main growth period;and(3) formation of narrow ring widths was closely related to drought stress, the development of wide ring widths will be restricted by increasing future temperatures. The VS model is applicable for radial growth simulation of subalpine coniferous forests and for guiding the cultivation of local tree species in the future.展开更多
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 evalua...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.展开更多
Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that to...Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that topography,as a proxy for resource availability,plays an important role in shaping tree species distributions in tropical forests.However,the association between growth stages and habitats types has not been considered in this analysis.Our aim was to examine the differences among different habitat types to determine whether tree species show similar species-habitat associations at young and mature life stages.Methods We used multivariate regression tree analysis to examined species-habitat associations among eight topographically defined habitats.The results were tested with a torus-translation test and canonical correspondence analysis(CCA)for 74 species in a 15 ha karst tropi-cal seasonal rain forest at the Nonggang National Natural Reserve in south China.We considered two life stages(young and mature)of trees species that showed a positive association with topography.Important Findings We found marked differences in community characteristics and number of associations among the eight habitats.Of the 74 species subjected to torus-translation test,63 had significant positive and 70 had significant negative associations with one or more of the eight habitats.Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower eleva-tion habitats.This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests.For the 63 tree species with significant positive associations to at least one habitat,40 of them had the same positive association at young and mature life stages.The CCA revealed that the six topographic variables considered had consistent relation-ships with species distribution among all individuals and their two life stages.This indicates that most of the karst forest tree species show consistent associations with a single habitat throughout their life.We conclude that niche differentiation plays an important role in main-taining the diversity of this heterogeneous species-rich karst forest.展开更多
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 as...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.展开更多
基金supported by Alpine timberline fluctuations and the response to climate change at centennial to millennial time scales in the Qinling Mountains (no.42371072)a General Programfrom the Natural Science Foundation of Shaanxi Province (no.2014JQ5172)+1 种基金the Open Fund Project of the State Key Laboratory of Loess and Quaternary Geology (no.SKLLQG1611)the National Forestry Public Welfare Industry Scientific Research Project of China (no.201304309).
文摘Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring formation to clarify the radial growth of trees. Tree-ring width standard chronology(STD) was established using samples of Larix principis-rupprechtii collected at 2303 m altitude on Luya Mountain. Using the Vaganov-Shashkin(VS) model to simulate growth and development, the internal physiological mechanism of radial growth is identified. It was concluded that:(1) the growing season of L. principis-rupprechtii was May to September;(2) soil moisture was a significant factor in the early and late growing seasons, and temperature was the dominant factor in its main growth period;and(3) formation of narrow ring widths was closely related to drought stress, the development of wide ring widths will be restricted by increasing future temperatures. The VS model is applicable for radial growth simulation of subalpine coniferous forests and for guiding the cultivation of local tree species in the future.
基金supported by the National Natural Science Foundation of China(31270562 and 31200329)the Chinese Forest Biodiversity Monitoring Network(29200931131101919)
文摘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.
基金National Natural Science Foundation of China(Grant Nos.31500342,31300359)the Guangxi Natural Science Foundation(2015GXNSFBA139050)the 2014‘Western Light’Project of the Chinese Academy of Sciences,and CFERN&GENE Award Funds on Ecological Paper.
文摘Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that topography,as a proxy for resource availability,plays an important role in shaping tree species distributions in tropical forests.However,the association between growth stages and habitats types has not been considered in this analysis.Our aim was to examine the differences among different habitat types to determine whether tree species show similar species-habitat associations at young and mature life stages.Methods We used multivariate regression tree analysis to examined species-habitat associations among eight topographically defined habitats.The results were tested with a torus-translation test and canonical correspondence analysis(CCA)for 74 species in a 15 ha karst tropi-cal seasonal rain forest at the Nonggang National Natural Reserve in south China.We considered two life stages(young and mature)of trees species that showed a positive association with topography.Important Findings We found marked differences in community characteristics and number of associations among the eight habitats.Of the 74 species subjected to torus-translation test,63 had significant positive and 70 had significant negative associations with one or more of the eight habitats.Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower eleva-tion habitats.This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests.For the 63 tree species with significant positive associations to at least one habitat,40 of them had the same positive association at young and mature life stages.The CCA revealed that the six topographic variables considered had consistent relation-ships with species distribution among all individuals and their two life stages.This indicates that most of the karst forest tree species show consistent associations with a single habitat throughout their life.We conclude that niche differentiation plays an important role in main-taining the diversity of this heterogeneous species-rich karst forest.
基金National Natural Science Foundation of China(31270562,30900178,31200329 and 31500337)Key Laboratory of Aquatic Botany and Watershed Ecology,CAS(Y455432J02)the Chinese Forest Biodiversity Monitoring Network(29200931131101919).
文摘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.
