Soil microbial communities are key factors in maintaining ecosystem multifunctionality(EMF).However,the distribution patterns of bacterial diversity and how the different bacterial taxa and their diversity dimensions ...Soil microbial communities are key factors in maintaining ecosystem multifunctionality(EMF).However,the distribution patterns of bacterial diversity and how the different bacterial taxa and their diversity dimensions affect EMF remain largely unknown.Here,we investigated variation in three measures of diversity(alpha diversity,community composition and network complexity)among rare,intermediate,and abundant taxa across a latitudinal gradient spanning five forest plots in Yunnan Province,China and examined their contributions on EMF.We aimed to characterize the diversity distributions of bacterial groups across latitudes and to assess the differences in the mechanisms underlying their contributions to EMF.We found that multifaceted diversity(i.e.,diversity assessed by the three different metrics)of rare,intermediate,and abundant bacteria generally decreased with increasing latitude.More importantly,we found that rare bacterial taxa tended to be more diverse,but they contributed less to EMF than intermediate or abundant bacteria.Among the three dimensions of diversity we assessed,only community composition significantly affected EMF across all locations,while alpha diversity had a negative effect,and network complexity showed no significant impact.Our study further emphasizes the importance of intermediate and abundant bacterial taxa as well as community composition to EMF and provides a theoretical basis for investigating the mechanisms by which belowground microorganisms drive EMF along a latitudinal gradient.展开更多
The decrease in species richness toward higher latitudes is an expected biogeographical pattern.This pattern could be related to particular envi-ronmental constraints and the evolutionary history of clades.However,spe...The decrease in species richness toward higher latitudes is an expected biogeographical pattern.This pattern could be related to particular envi-ronmental constraints and the evolutionary history of clades.However,species richness does not fully represent the evolutionary history of the clades behind their distributions.Phylogenetic diversity better clarifies the role of historical factors in biogeographical patterns.We analyzed envi-ronmental and historical drivers related to latitudinal variation in species richness and phylogenetic diversity of Atlantic Forest endemic snakes.We implemented species distribution models,from voucherbased locality points,to map the snake ranges and diversity.We used generalized additive mixed models to evaluate the relationships among the diversity metrics and area,topographical roughness,and past climate change velocity since the Last Maximum Glacial in the Atlantic Forest latitudinal gradient.Contrary to the expected general pattern,species richness was higher toward higher latitudes,being positively related to past climatic stability.Species richness also increased with total area and higher topographical roughness.Phylogenetic diversity,on the other hand,showed opposite relationships related to the same factors.Phylogenetic diversity increased with lower climatic stability in lower latitudes.Thus,dimensions of diversity were affected in different ways by historical and environmental constraints in this unique and threatened biodiversity hotspot.展开更多
Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in fa...Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in farmlands of Songliao Plain, Northeast China to assess the impact of climatic changes along the latitudinal transect on nutrient cycling in agroecosystems. Top soils （0-20 cm depth） were sampled in fields at 7 locations from north （Hallun） to south （Dashiqiao） in the end of October 2005 after maize harvest. The contents of total C, N, and P, C/N, available N, and available P increased with the latitude. The activities of invertase and acid phosphatase, microbial biomass （MB） C and N, and MBC/MBN were significantly correlated with latitude （P 〈 0.05, r^2 = 0.198, 0.635, 0.558, 0.211 and 0.317, respectively）, that is, increasing with the latitude. Significant positive correlations （P 〈 0.05） were observed between invertase activity and the total N and available P, and between acid phosphatase activity and the total C, C/N, available N, total P and available P. The urease, acid phosphatase, and dehydrogenase activities were significantly correlated with the soil pH and electrical conductivity （EC） （P 〈 0.05）. MBC and MBN were positively correlated with the total C, C/N, and available P （P 〈 0.05）. The MBC/MBN ratio was positively correlated with the total C, total N, C/N, and available N （P 〈 0.05）. The spatial distribution of soil enzyme activities and microbial biomass resulted from the changes in soil properties such as soil organic matter, soil pH, and EC, partially owing to variations in temperature and rainfall along the latitudinal gradient.展开更多
Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera phi...Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera philoxeroides,in its terrestrial habitat in China through a large-scale latitudinal field investigation.Methods We established 59 plots along the latitudinal transect from 21°N to 37°N.We recorded species name,abundance,height and individual species coverage of plants in every quadrat.We then measuredα-species diversity variations associated with the A.philoxeroides community across the latitudinal range.We also analyzed the effect of latitude on plant species’distributions in this community by using canonical correspondence analysis(CCA).Important Findings We found that species cover and importance value of A.philoxe-roides increased in areas<35°N,but decreased at higher latitudes.Lower latitudes supported greater species diversity than higher latitudes.Small-scale invasion of A.philoxeroides was associated with higher species diversity,but community diversity was lower when A.philoxeroides species cover exceeded 36%.Community plant species changed from mesophyte to hygrophyte gradually from low to high latitude.Our research suggests that latitude had significant influences on community diversity which interacted with the biotic resistance of a community and impact of invasion.Consequently,A.philoxeroides may become more invasive and have greater negative impacts on community species diversity in higher latitudes as global climate changes.展开更多
In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fun...In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fungal communities vary with latitude.We collected soil samples from 17 forests,along a latitudinal transect in western China.Forest types covered included boreal,temperate,subtropical and tropical forests.We used 454 pyrosequencing techniques to analyze the soil communities.These data were correlated with abiotic and biotic variables to determine which factors most strongly influenced fungal community composition.Our results indicated that temperature,latitude,and plant diversity most strongly influence soil fungal community composition.Fungal diversity patterns were unimodal,with temperate forests(mid latitude)exhibiting the greatest diversity.Furthermore,these diversity patterns indicate that fungal diversity was highest in the forest systems with the lowest tree diversity(temperate forests).Different forest systems were dominated by different fungal subgroups,ectomycorrhizal fungi dominated in boreal and temperate forests;endomycorrhizal fungi dominated in the tropical rainforests,and non-mycorrhizal fungi were best represented in subtropical forests.Our results suggest that soil fungal communities are strongly dependent on vegetation type,with fungal diversity displaying an inverse relationship to plant diversity.展开更多
Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean z...Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean zonal wind （ ζ ）. The result shows that ζ increases with altitudes and displays clearly seasonal and interannual variability. In the upper meso- sphere and lower thermosphere （MLT）, at the latitudes between 20°N and 20°S, when ζ strengthens （weakens） at equinoxes （solstices） the DW1 amplitude increases （decreases） simultaneously. Stronger maximum in March-April equinox occurs in both ζ and the DW1 amplitude. Besides, a quasi-biennial oscillation of DW1 is also found to be synchronous with ζ. The resembling spatial-temporal features suggest that ζ in the upper tropic MLT probably plays an important role in modulating semiannual, annual, and quasi-biennial oscillations in DW1 at the same latitude and altitude. In addition, ζ in the meso- sphere possibly affects the propagation of DW1 and produces SAO of DW1 in the lower thermosphere. Thus, SAO of DW1 in the upper MLT may be a combined effect of ζ both in the mesosphere and in the upper MLT, which models studies should determine in the future.展开更多
Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefor...Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics.Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms.Here,we studied morphological traits in breeding Eurasian tree sparrows(ETSs;Passer montanus)among low-latitude(Yunnan and Hunan)and middle-latitude(Hebei)localities in China.We then compared body mass;lengths of bill,tarsometatarsus,wing,total body,and tail feather;and baseline and capture stress-induced levels of plasma corticosterone(CORT)and the metabolites including glucose(Glu),total triglyceride(TG),free fatty acid(FFA),total protein,and uric acid(UA).None of the measured morphological parameters varied with latitude except in the Hunan population,which demonstrated longer bills than those in other populations.Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude,but total integrated CORT levels did not vary with latitude.Capture stress-induced significantly increased Glu levels and decreased TG levels,independent of site.However,the Hunan population had significantly higher baseline CORT,baseline and stress-induced FFA levels,but lower UA levels,which differed from other populations.Our results suggest that rather than morphological adjustments,physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs.It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.展开更多
Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gam...Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gamma diversity after accounting for beta diversity.Methods Correlation and regression analyses were used to relate beta and gamma diversity to latitude along two latitudinal gradients in the New World(one including 72 forest sites located south of the equator and the other including 79 forest sites located north of the equator).Important Findings Beta diversity and gamma diversity were negatively correlated with latitude.Beta diversity was strongly and positively correlated with gamma diversity(Pearson’s correlation coefficient:0.783 for New World North and 0.848 for New World South).When beta diversity was regressed on latitude and gamma diversity,69.8 and 85.7%of the variation in beta diversity were explained,respectively,for New World North and New World South.When gamma diversity was regressed on latitude and beta diversity,81.8 and 84.3%of the variation in gamma diversity were explained,respectively,for New World North and New World South.After statistically removing the relationship between beta and gamma diversity,latitude has weak or no relationships with beta and gamma diversity.However,strong positive correlations between beta and gamma diversity may not be considered as evidence of one driving the other along a latitudinal gradient.展开更多
Urbanization has significantly altered the habitat structure and behavioral patterns of animals.In urban environments with frequent human disturbances,animals may undergo adaptive adjustments in their escape behaviors...Urbanization has significantly altered the habitat structure and behavioral patterns of animals.In urban environments with frequent human disturbances,animals may undergo adaptive adjustments in their escape behaviors.This study focuses on Eurasian Tree Sparrows(Passer montanus)from five cities across different latitudes in China,comparing their flight initiation distance(FID)in urban and rural areas to assess the impact of urbanization on their escape behavior and the trend of ecological homogenization.The results confirm the established pattern at the geographic level:a reduction of FID in urban habitats and a decrease in FID with increasing latitude.That is,northern populations of the Eurasian Tree Sparrow in China are bolder than the southern populations.In addition,FID is positively correlated with flock size,with rural flocks exhibiting more pronounced group behavior(observed flocking frequency for urban and rural is 28.74%vs.40.7%,flock size variance is 26.90 vs.55.63).Despite the differences between northern and southern latitudes,the variability of FID in urban individuals consistently remains lower than that in rural areas,supporting the trend of reduced variability in escape behavior among birds in urban environments.Driven by urbanization,the escape behavior of Eurasian Tree Sparrows tends toward ecological homogenization,meaning that behavioral differences between urban areas in different cities are diminishing.This trend may obscure the behavioral variability brought about by latitude gradients,indicating that urbanization not only shapes the behavioral adaptations of birds but also potentially weakens their behavioral diversity.展开更多
Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major...Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20°in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World)are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.展开更多
Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects ...Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.展开更多
The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flower...The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.展开更多
Leaf functional traits reflect the ecological strategies of plants and influence their growth and distribution.While variation in leaf traits has been extensively documented across species in terrestrial ecosystems,st...Leaf functional traits reflect the ecological strategies of plants and influence their growth and distribution.While variation in leaf traits has been extensively documented across species in terrestrial ecosystems,studies in wetland ecosystems can enhancethe understanding of leaf trait variation along environmental gradients.Intraspecific studies are particularly valuable for exploring trait variation and its underlying mechanism.Coastal wetlands have become hotspots for studying trait variation,and the invasive Spartina alterniflora,distributed along China's coastline,is an ideal species for investigating leaf traits variation.We examined the geographical variation and abiotic drivers of six leaf functional traits and explored the roles of phenotypic plasticity and genetic differentiation through a two-year common garden experiment.We also analyzed the relationships between leaf traits and growth performance in both field and common garden.All leaf traits exhibited significant geographical variation,which were affected by both climatic and sedimentary variables.Common garden experiment exhibited trait-dependent response,with different leaf traits showing varying degrees of plastic response or genetic differentiation.Variation in leaf size,leaf thickness and specific leaf area was primarily driven by genetic differentiation,while variation in leaf density and leaf dry matter content was largely due to phenotypic plasticity.Leaf size and thickness were positively correlated with growth performance in both field and common garden.This study advances the understanding of leaf trait variation in terrestrial ecosystems and highlights how multiple abiotic variables shape latitudinal patterns in leaf traits.The resource acquisition strategy at high latitudes in the northern hemisphere contributes to the strong growth performance of S.alterniflora,potentially facilitating its northward expansion.In contrast,the resource conservation strategy at low latitudes may hinder its southward expansion.展开更多
Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We eva...Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We evaluate the influence of altitude and climatic variables related to temperature and precipitation on plant community composition and species richness on Brazilian inselbergs.We assume as a premise that both climate and altitude would induce changes on plant community composition and species richness at the local level.We used plant inventory data from 370 sampling units across four inselberg sites in the Atlantic Forest of Espírito Santo State,south-eastern Brazil.We tested the univariate and multivariate effects of altitude and climate variables on community composition and species richness with multiple models.Differences in species richness between inselbergs were evaluated using sample-based data to estimate rarefaction and extrapolation curves.In addition,differences in species composition and taxonomic beta diversity were examined via novel frequency-based metrics.A contrasting climate pattern was observed between the inselberg sites,with south sites being wet compared to the dry conditions found in northern sites.Species richness by rarefaction showed a similar pattern within regional sites;however,there were marked differences between regions.Species richness and beta diversity showed significant differences among sites,with higher values in southern sites than in northern sites.In a multi-model comparison between inselberg sites,altitude significantly influenced community composition and species richness and explained more variance than climate models.This finding suggested that climate could act to some extent on these tropical inselbergs;however,altitude was a better predictor of plant community composition and species richness at the local level.展开更多
The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether...The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.展开更多
In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-lea...In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-leaved plants to respond to harsh climatic conditions(e.g.,greater seasonality).The advantages of deciduous leaf habit over evergreen leaf habit in more seasonal climates have led us to hypothesize that leaf habits would shift in response to climate changes more conspicuously in forest canopy trees than in forest understory shrubs.Furthermore,we hypothesize that in the forests of the subtropics,plants at higher latitudes,regardless of growth form,would better tolerate seasonal harsh climates,and hence show less differentiation in leaf habit shift,compared to those at lower latitudes.To test these two hypotheses,we modelled the proportion of deciduous broad-leaved species and the incidence of deciduous and evergreen broad-leaved species in woody angiosperm species compositions of ten largesized forest plots distributed in the Chinese subtropics.We found that the rate of leaf habit shift along a latitudinal gradient was higher in forest trees than in forest shrubs.We also found that the differentiation in leaf habit shift between trees and shrubs is greater at lower latitudes(i.e.,warmer climates)than at higher latitudes(i.e.,colder climates).These findings indicate that specialized forest plants are differentially affected by climate in distinct forest strata in a manner dependent on latitudinal distribution.These differences in forest plant response to changes in climate suggest that global climate warming will alter growth forms and geographical distributions and ranges of forests.展开更多
Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing ari...Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.展开更多
Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal ...Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.展开更多
Background： Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes （BEF） has been a central issue in biodiversity studies. Although m...Background： Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes （BEF） has been a central issue in biodiversity studies. Although many hypotheses have been developed to interpret global gradients of biodiversity, there has not been complete agreement on mechanisms controlling biodiversity patterns and distributions. Differences may be due to limited observation data and inconsistencies of spatial scales in analysis. Methods： In this study, we take advantage of USDA Forest Service forest inventory and analysis （FIA） data for exploring regional forest biodiversity and BEF in New England forests. The FIA data provide detailed information of sampled plots and trees for the region, including 6000 FIA plots and more than 33,000 individual trees. Biodiversity models were used to analyze the data. Results： Tree species diversity increases from the north to the south at a rate about 2-3 species per latitudinal degree. Tree species diversity is better predicted by tree height than forest age or biomass. Very different distribution patterns of two common maple species, sugar maple （Acer sdcchorum） and red maple （Acer rubrum）, highlight the vulnerability of sugar maple and its potential replacement by red maple on New England landscapes. Red maple generally already outperforms sugar maple, and will likely and continuously benefit from a changing climate in New England. Conclusions： We conclude that forest structure （height） and resources （biomass） are more likely foundational characteristics supporting biodiversity rather than biodiversity determining forest productivity and/or biomass. The potential replacement of red maple for sugar maple in the New England areas could affect biodiversity and stability of forest ecosystem functioning because sugar maple plays important ecological roles distinct from red maple that are beneficial to other tree species in northern hardwood forests. Such a change may not affect forest resilience in terms of forest productivity and biomass as these are similar in red maple and sugar maple, however, it would almost certainly alter forest structure across the landscape.展开更多
基金supported by the Fundamental Research Funds of Chinese Academy of Forestry(Nos.CAFYBB2022SY037,CAFYBB2021ZA002 and CAFYBB2022QC002)the Basic Research Foundation of Yunnan Province(Grant No.202201AT070264).
文摘Soil microbial communities are key factors in maintaining ecosystem multifunctionality(EMF).However,the distribution patterns of bacterial diversity and how the different bacterial taxa and their diversity dimensions affect EMF remain largely unknown.Here,we investigated variation in three measures of diversity(alpha diversity,community composition and network complexity)among rare,intermediate,and abundant taxa across a latitudinal gradient spanning five forest plots in Yunnan Province,China and examined their contributions on EMF.We aimed to characterize the diversity distributions of bacterial groups across latitudes and to assess the differences in the mechanisms underlying their contributions to EMF.We found that multifaceted diversity(i.e.,diversity assessed by the three different metrics)of rare,intermediate,and abundant bacteria generally decreased with increasing latitude.More importantly,we found that rare bacterial taxa tended to be more diverse,but they contributed less to EMF than intermediate or abundant bacteria.Among the three dimensions of diversity we assessed,only community composition significantly affected EMF across all locations,while alpha diversity had a negative effect,and network complexity showed no significant impact.Our study further emphasizes the importance of intermediate and abundant bacterial taxa as well as community composition to EMF and provides a theoretical basis for investigating the mechanisms by which belowground microorganisms drive EMF along a latitudinal gradient.
基金supported by grants from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo(FAPESP 2014/23677-9 and 2020/12658-4)Conselho Nacional de Desenvolvimento Cientifico e Tecnol6gico(CNPq,405447/2016-7).R.J.S.thanks CNPq for the research fellowship(307956/2022-9).J.A.R.A.thanks Instituto Serrapilheira for the postdoctoral fellowship.
文摘The decrease in species richness toward higher latitudes is an expected biogeographical pattern.This pattern could be related to particular envi-ronmental constraints and the evolutionary history of clades.However,species richness does not fully represent the evolutionary history of the clades behind their distributions.Phylogenetic diversity better clarifies the role of historical factors in biogeographical patterns.We analyzed envi-ronmental and historical drivers related to latitudinal variation in species richness and phylogenetic diversity of Atlantic Forest endemic snakes.We implemented species distribution models,from voucherbased locality points,to map the snake ranges and diversity.We used generalized additive mixed models to evaluate the relationships among the diversity metrics and area,topographical roughness,and past climate change velocity since the Last Maximum Glacial in the Atlantic Forest latitudinal gradient.Contrary to the expected general pattern,species richness was higher toward higher latitudes,being positively related to past climatic stability.Species richness also increased with total area and higher topographical roughness.Phylogenetic diversity,on the other hand,showed opposite relationships related to the same factors.Phylogenetic diversity increased with lower climatic stability in lower latitudes.Thus,dimensions of diversity were affected in different ways by historical and environmental constraints in this unique and threatened biodiversity hotspot.
基金the National Key Basic Research Support Foundation of China (No.2005CB121105)theNational Natural Science Foundation of China (No.30670379).
文摘Soil enzymes activities and microbial biomass have an important influence on nutrient cycling. The spatial distribution of soil enzymes activities and microbial biomass were examined along a latitudinal gradient in farmlands of Songliao Plain, Northeast China to assess the impact of climatic changes along the latitudinal transect on nutrient cycling in agroecosystems. Top soils （0-20 cm depth） were sampled in fields at 7 locations from north （Hallun） to south （Dashiqiao） in the end of October 2005 after maize harvest. The contents of total C, N, and P, C/N, available N, and available P increased with the latitude. The activities of invertase and acid phosphatase, microbial biomass （MB） C and N, and MBC/MBN were significantly correlated with latitude （P 〈 0.05, r^2 = 0.198, 0.635, 0.558, 0.211 and 0.317, respectively）, that is, increasing with the latitude. Significant positive correlations （P 〈 0.05） were observed between invertase activity and the total N and available P, and between acid phosphatase activity and the total C, C/N, available N, total P and available P. The urease, acid phosphatase, and dehydrogenase activities were significantly correlated with the soil pH and electrical conductivity （EC） （P 〈 0.05）. MBC and MBN were positively correlated with the total C, C/N, and available P （P 〈 0.05）. The MBC/MBN ratio was positively correlated with the total C, total N, C/N, and available N （P 〈 0.05）. The spatial distribution of soil enzyme activities and microbial biomass resulted from the changes in soil properties such as soil organic matter, soil pH, and EC, partially owing to variations in temperature and rainfall along the latitudinal gradient.
基金Knowledge Innovation Program of Wuhan Botanical Garden(Y455437H05)supported by a National Science Foundation Postdoctoral Research Fellowship.
文摘Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera philoxeroides,in its terrestrial habitat in China through a large-scale latitudinal field investigation.Methods We established 59 plots along the latitudinal transect from 21°N to 37°N.We recorded species name,abundance,height and individual species coverage of plants in every quadrat.We then measuredα-species diversity variations associated with the A.philoxeroides community across the latitudinal range.We also analyzed the effect of latitude on plant species’distributions in this community by using canonical correspondence analysis(CCA).Important Findings We found that species cover and importance value of A.philoxe-roides increased in areas<35°N,but decreased at higher latitudes.Lower latitudes supported greater species diversity than higher latitudes.Small-scale invasion of A.philoxeroides was associated with higher species diversity,but community diversity was lower when A.philoxeroides species cover exceeded 36%.Community plant species changed from mesophyte to hygrophyte gradually from low to high latitude.Our research suggests that latitude had significant influences on community diversity which interacted with the biotic resistance of a community and impact of invasion.Consequently,A.philoxeroides may become more invasive and have greater negative impacts on community species diversity in higher latitudes as global climate changes.
基金This study was supported by grants from Ministry of Science and Technology(MOST)of China(973 Program No.2012CB416904)National Natural Science Foundation of China(No.90302013)+2 种基金Natural Science Foundation of Yunnan(2005C0056M)Wang K.C.Foundation,and grants(DEB-0620910,DEB-0218039)from U.S.National Science FoundationThe work was also partially funded by the CG Research Program 6:Forests,Trees and Agroforestry.ADNA sequence data are available via GenBank(accession no.KF411754-KF412201).
文摘In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fungal communities vary with latitude.We collected soil samples from 17 forests,along a latitudinal transect in western China.Forest types covered included boreal,temperate,subtropical and tropical forests.We used 454 pyrosequencing techniques to analyze the soil communities.These data were correlated with abiotic and biotic variables to determine which factors most strongly influenced fungal community composition.Our results indicated that temperature,latitude,and plant diversity most strongly influence soil fungal community composition.Fungal diversity patterns were unimodal,with temperate forests(mid latitude)exhibiting the greatest diversity.Furthermore,these diversity patterns indicate that fungal diversity was highest in the forest systems with the lowest tree diversity(temperate forests).Different forest systems were dominated by different fungal subgroups,ectomycorrhizal fungi dominated in boreal and temperate forests;endomycorrhizal fungi dominated in the tropical rainforests,and non-mycorrhizal fungi were best represented in subtropical forests.Our results suggest that soil fungal communities are strongly dependent on vegetation type,with fungal diversity displaying an inverse relationship to plant diversity.
基金supported by the National Natural Science Foundation of China(Grant Nos.41274153&41331069)the National Important Basic Research Project of China(Grant No.2011CB811405)+2 种基金the Chinese Academy of Sciences(Grant No.KZZD-EW-01-2)supported by the Specialized Research Fund for State Key Laboratoriesperformed by Numerical Forecast Modelling R&D and VR System of State Key Lab.of Space Weather and Special HPC work stand of Chinese Meridian Project
文摘Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean zonal wind （ ζ ）. The result shows that ζ increases with altitudes and displays clearly seasonal and interannual variability. In the upper meso- sphere and lower thermosphere （MLT）, at the latitudes between 20°N and 20°S, when ζ strengthens （weakens） at equinoxes （solstices） the DW1 amplitude increases （decreases） simultaneously. Stronger maximum in March-April equinox occurs in both ζ and the DW1 amplitude. Besides, a quasi-biennial oscillation of DW1 is also found to be synchronous with ζ. The resembling spatial-temporal features suggest that ζ in the upper tropic MLT probably plays an important role in modulating semiannual, annual, and quasi-biennial oscillations in DW1 at the same latitude and altitude. In addition, ζ in the meso- sphere possibly affects the propagation of DW1 and produces SAO of DW1 in the lower thermosphere. Thus, SAO of DW1 in the upper MLT may be a combined effect of ζ both in the mesosphere and in the upper MLT, which models studies should determine in the future.
基金We thank Yinchao Hao and Wande Li for their assistance with sample collection.This study was funded by the National Natural Science Foundation of China(NSFC,31971413)Natural Science Foundation of Hebei Province(NSFHP,C2020205038)to D.L.Science and Technology Project of Hebei Education Department(QN2019103)to Y.S.
文摘Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics.Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms.Here,we studied morphological traits in breeding Eurasian tree sparrows(ETSs;Passer montanus)among low-latitude(Yunnan and Hunan)and middle-latitude(Hebei)localities in China.We then compared body mass;lengths of bill,tarsometatarsus,wing,total body,and tail feather;and baseline and capture stress-induced levels of plasma corticosterone(CORT)and the metabolites including glucose(Glu),total triglyceride(TG),free fatty acid(FFA),total protein,and uric acid(UA).None of the measured morphological parameters varied with latitude except in the Hunan population,which demonstrated longer bills than those in other populations.Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude,but total integrated CORT levels did not vary with latitude.Capture stress-induced significantly increased Glu levels and decreased TG levels,independent of site.However,the Hunan population had significantly higher baseline CORT,baseline and stress-induced FFA levels,but lower UA levels,which differed from other populations.Our results suggest that rather than morphological adjustments,physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs.It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.
文摘Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gamma diversity after accounting for beta diversity.Methods Correlation and regression analyses were used to relate beta and gamma diversity to latitude along two latitudinal gradients in the New World(one including 72 forest sites located south of the equator and the other including 79 forest sites located north of the equator).Important Findings Beta diversity and gamma diversity were negatively correlated with latitude.Beta diversity was strongly and positively correlated with gamma diversity(Pearson’s correlation coefficient:0.783 for New World North and 0.848 for New World South).When beta diversity was regressed on latitude and gamma diversity,69.8 and 85.7%of the variation in beta diversity were explained,respectively,for New World North and New World South.When gamma diversity was regressed on latitude and beta diversity,81.8 and 84.3%of the variation in gamma diversity were explained,respectively,for New World North and New World South.After statistically removing the relationship between beta and gamma diversity,latitude has weak or no relationships with beta and gamma diversity.However,strong positive correlations between beta and gamma diversity may not be considered as evidence of one driving the other along a latitudinal gradient.
基金supported by the National Key R&D Program of China(2023YFF1304600)。
文摘Urbanization has significantly altered the habitat structure and behavioral patterns of animals.In urban environments with frequent human disturbances,animals may undergo adaptive adjustments in their escape behaviors.This study focuses on Eurasian Tree Sparrows(Passer montanus)from five cities across different latitudes in China,comparing their flight initiation distance(FID)in urban and rural areas to assess the impact of urbanization on their escape behavior and the trend of ecological homogenization.The results confirm the established pattern at the geographic level:a reduction of FID in urban habitats and a decrease in FID with increasing latitude.That is,northern populations of the Eurasian Tree Sparrow in China are bolder than the southern populations.In addition,FID is positively correlated with flock size,with rural flocks exhibiting more pronounced group behavior(observed flocking frequency for urban and rural is 28.74%vs.40.7%,flock size variance is 26.90 vs.55.63).Despite the differences between northern and southern latitudes,the variability of FID in urban individuals consistently remains lower than that in rural areas,supporting the trend of reduced variability in escape behavior among birds in urban environments.Driven by urbanization,the escape behavior of Eurasian Tree Sparrows tends toward ecological homogenization,meaning that behavioral differences between urban areas in different cities are diminishing.This trend may obscure the behavioral variability brought about by latitude gradients,indicating that urbanization not only shapes the behavioral adaptations of birds but also potentially weakens their behavioral diversity.
文摘Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20°in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World)are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.
文摘Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.
基金supported by the National Natural Science Foundation of China (Grant number 42261004)supported by the Jiangsu Social Development Project (BE2022792)。
文摘The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.
基金the National Key R&D Program of China(2022YFC3105401)This research was also supported by the National Science Foundation of China(32025026)China Postdoctoral Science Foundation(2022M722653).
文摘Leaf functional traits reflect the ecological strategies of plants and influence their growth and distribution.While variation in leaf traits has been extensively documented across species in terrestrial ecosystems,studies in wetland ecosystems can enhancethe understanding of leaf trait variation along environmental gradients.Intraspecific studies are particularly valuable for exploring trait variation and its underlying mechanism.Coastal wetlands have become hotspots for studying trait variation,and the invasive Spartina alterniflora,distributed along China's coastline,is an ideal species for investigating leaf traits variation.We examined the geographical variation and abiotic drivers of six leaf functional traits and explored the roles of phenotypic plasticity and genetic differentiation through a two-year common garden experiment.We also analyzed the relationships between leaf traits and growth performance in both field and common garden.All leaf traits exhibited significant geographical variation,which were affected by both climatic and sedimentary variables.Common garden experiment exhibited trait-dependent response,with different leaf traits showing varying degrees of plastic response or genetic differentiation.Variation in leaf size,leaf thickness and specific leaf area was primarily driven by genetic differentiation,while variation in leaf density and leaf dry matter content was largely due to phenotypic plasticity.Leaf size and thickness were positively correlated with growth performance in both field and common garden.This study advances the understanding of leaf trait variation in terrestrial ecosystems and highlights how multiple abiotic variables shape latitudinal patterns in leaf traits.The resource acquisition strategy at high latitudes in the northern hemisphere contributes to the strong growth performance of S.alterniflora,potentially facilitating its northward expansion.In contrast,the resource conservation strategy at low latitudes may hinder its southward expansion.
文摘Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We evaluate the influence of altitude and climatic variables related to temperature and precipitation on plant community composition and species richness on Brazilian inselbergs.We assume as a premise that both climate and altitude would induce changes on plant community composition and species richness at the local level.We used plant inventory data from 370 sampling units across four inselberg sites in the Atlantic Forest of Espírito Santo State,south-eastern Brazil.We tested the univariate and multivariate effects of altitude and climate variables on community composition and species richness with multiple models.Differences in species richness between inselbergs were evaluated using sample-based data to estimate rarefaction and extrapolation curves.In addition,differences in species composition and taxonomic beta diversity were examined via novel frequency-based metrics.A contrasting climate pattern was observed between the inselberg sites,with south sites being wet compared to the dry conditions found in northern sites.Species richness by rarefaction showed a similar pattern within regional sites;however,there were marked differences between regions.Species richness and beta diversity showed significant differences among sites,with higher values in southern sites than in northern sites.In a multi-model comparison between inselberg sites,altitude significantly influenced community composition and species richness and explained more variance than climate models.This finding suggested that climate could act to some extent on these tropical inselbergs;however,altitude was a better predictor of plant community composition and species richness at the local level.
基金Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP procs.2008/50068-2,2014/23677-9 and 2020/12658-4)Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq,405447/2016-7)RJS thanks CNPq for the research fellowship(312795/2018-1).
文摘The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.
基金supported by the Natural Science and Technology Foundation of Guizhou Province[[2020]1Z013]the Joint Fund of the National Natural Science Foundation of Chinathe Karst Science Research Center of Guizhou Province[U1812401]。
文摘In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-leaved plants to respond to harsh climatic conditions(e.g.,greater seasonality).The advantages of deciduous leaf habit over evergreen leaf habit in more seasonal climates have led us to hypothesize that leaf habits would shift in response to climate changes more conspicuously in forest canopy trees than in forest understory shrubs.Furthermore,we hypothesize that in the forests of the subtropics,plants at higher latitudes,regardless of growth form,would better tolerate seasonal harsh climates,and hence show less differentiation in leaf habit shift,compared to those at lower latitudes.To test these two hypotheses,we modelled the proportion of deciduous broad-leaved species and the incidence of deciduous and evergreen broad-leaved species in woody angiosperm species compositions of ten largesized forest plots distributed in the Chinese subtropics.We found that the rate of leaf habit shift along a latitudinal gradient was higher in forest trees than in forest shrubs.We also found that the differentiation in leaf habit shift between trees and shrubs is greater at lower latitudes(i.e.,warmer climates)than at higher latitudes(i.e.,colder climates).These findings indicate that specialized forest plants are differentially affected by climate in distinct forest strata in a manner dependent on latitudinal distribution.These differences in forest plant response to changes in climate suggest that global climate warming will alter growth forms and geographical distributions and ranges of forests.
基金funding by project RTI2018–096884-B-C31(Spanish Ministry of Science)G.S-B.is supported by a Spanish Ministry of Economy,Industry+1 种基金Competitiveness Postdoctoral grant(FJCI 2016–30121FEDER funds)。
文摘Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.
基金supported by a grant form the National Key Research and Development Program,No.2019YFA0607302。
文摘Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.
基金the project NRS-6“Climate,Fire,and Carbon Cycle Sciences”supported by the USDA Forest ServiceBeijing Forestry University for covering the trip to the conference and generous conference venue facilitating this study
文摘Background： Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes （BEF） has been a central issue in biodiversity studies. Although many hypotheses have been developed to interpret global gradients of biodiversity, there has not been complete agreement on mechanisms controlling biodiversity patterns and distributions. Differences may be due to limited observation data and inconsistencies of spatial scales in analysis. Methods： In this study, we take advantage of USDA Forest Service forest inventory and analysis （FIA） data for exploring regional forest biodiversity and BEF in New England forests. The FIA data provide detailed information of sampled plots and trees for the region, including 6000 FIA plots and more than 33,000 individual trees. Biodiversity models were used to analyze the data. Results： Tree species diversity increases from the north to the south at a rate about 2-3 species per latitudinal degree. Tree species diversity is better predicted by tree height than forest age or biomass. Very different distribution patterns of two common maple species, sugar maple （Acer sdcchorum） and red maple （Acer rubrum）, highlight the vulnerability of sugar maple and its potential replacement by red maple on New England landscapes. Red maple generally already outperforms sugar maple, and will likely and continuously benefit from a changing climate in New England. Conclusions： We conclude that forest structure （height） and resources （biomass） are more likely foundational characteristics supporting biodiversity rather than biodiversity determining forest productivity and/or biomass. The potential replacement of red maple for sugar maple in the New England areas could affect biodiversity and stability of forest ecosystem functioning because sugar maple plays important ecological roles distinct from red maple that are beneficial to other tree species in northern hardwood forests. Such a change may not affect forest resilience in terms of forest productivity and biomass as these are similar in red maple and sugar maple, however, it would almost certainly alter forest structure across the landscape.
