Climatic correlates of phylogenetic relatedness of woody angiosperms in forest communities along a tropical elevational gradient in South America

Aims This study assesses the relationship between phylogenetic relatedness of angiosperm tree species and climatic variables in local forests distributed along a tropical elevational gradient in South America. In particular, this paper addresses two questions: Is phylogenetic relatedness of plant species in communities related to temperature variables more strongly than to water variables for tropical elevational gradients? Is phylogenetic relatedness of plant species in communities driven by extreme climatic conditions (e.g. minimum temperature (MT) and water deficit) more strongly than by climatic seasonal variability (e.g. temperature seasonality and precipitation seasonality)?Methods I used a set of 34 angiosperm woody plant assemblages along an elevational gradient in the Andes within less than 5 degrees of the equator. Phylogenetic relatedness was quantified as net relatedness index (NRI) and nearest taxon index (NTI) and was related to major climatic variables. Correlation analysis and structure equation modeling approach were used to assess the relationships between phylogenetic relatedness and climatic variables.Important findings Phylogenetic relatedness of angiosperm woody species in the local forest communities is more strongly associated with temperature-related variables than with water-related variables, is positively correlated with mean annual temperature (MAT) and MT, and is related with extreme cold temperature more strongly than with seasonal temperature variability. NTI was related with elevation, MAT and MT more strongly than was NRI. Niche convergence, rather than niche conservatism, has played a primary role in driving community assembly in local forests along the tropical elevational gradient examined. Negative correlations of phylogenetic relatedness with elevation and higher correlations of phylogenetic relatedness with elevation and temperature for NTI than for NRI indicate that evolution of cold tolerance at high elevations in tropical regions primarily occurred at recent (terminal) phylogenetic nodes widely distributed among major clades.     

Constant tree species richness along an elevational gradient of Mt. Bokor,a table-shaped mountain in southwestern Cambodia

Some previous studies along an elevational gradient on a tropical mountain documented that plant species richness decreases with increasing elevation. However, most of studies did not attempt to standardize the amount of sampling effort. In this paper, we employed a standardized sampling effort to study tree species richness along an elevational gradient on Mt. Bokor, a table-shaped mountain in southwestern Cambodia, and examined relationships between tree species richness and environmental factors. We used two methods to record tree species richness: first, we recorded trees taller than 4 m in 20 uniform plots (5 × 100 m) placed at 266–1048-m elevation; and second, we collected specimens along an elevational gradient from 200 to 1048 m. For both datasets, we applied rarefaction and a Chao1 estimator to standardize the sampling efforts. A generalized linear model (GLM) was used to test the relationship of species richness with elevation. We recorded 308 tree species from 20 plots and 389 tree species from the general collections. Species richness observed in 20 plots had a weak but non-significant correlation with elevation. Species richness estimated by rarefaction or Chao1 from both data sets also showed no significant correlations with elevation. Unlike many previous studies, tree species richness was nearly constant along the elevational gradient of Mt. Bokor where temperature and precipitation are expected to vary. We suggest that the table-shaped landscape of Mt. Bokor, where elevational interval areas do not significantly change between 200 and 900 m, may be a determinant of this constant species richness.     

Elevational patterns of plant richness and their drivers on an Asian mountain

We examined the elevational patterns of plant species along two transects on Mt Seorak, South Korea, and calculated four richness indices from field survey data: total number of species per 100 m elevational band; mean number of species per plot in each elevational band; total estimated number of species per elevational band; and beta diversity of each elevational band. We evaluated the effects of area, mean distance between plots, climatic variables (mean annual temperature and precipitation), and productivity on the richness patterns along the two transects. In total, 235 plant species belonging to 72 families and 161 genera were recorded from 130 plots along the two transects. The analyses revealed different patterns including monotonic decline, and unimodal and multimodal shapes for richness indices of total, woody, and herbaceous plants with the change in elevation along the two transects. The proportion of suitable area (as opposed to rocky areas) was the best predictor for total number of species per elevational band, mean number of species per plot, and total estimated number of species per elevational band of total and herbaceous plants along the two transects. Mean distance between plots was the most important variable for beta diversity of all plant groups. Although regional area, climatic variables, and productivity were important variables for predicting woody plant richness patterns, the effects were not consistent between the two transects. Our study suggests that elevational species richness patterns may differ not only among different plant groups, but also between nearby elevational transects, and that these differences are explained by differences in the underlying mechanisms shaping these patterns.     

Patterns of ant species richness along elevational gradients in an arid ecosystem

Aim In this study, we examine patterns of local and regional ant species richness along three elevational gradients in an arid ecosystem. In addition, we test the hypothesis that changes in ant species richness with elevation are related to elevation‐dependent changes in climate and available area. Location Spring Mountains, Nevada, U.S.A. Methods We used pitfall traps placed at each 100‐m elevational band in three canyons in the Spring Mountains. We compiled climate data from 68 nearby weather stations. We used multiple regression analysis to examine the effects of annual precipitation, average July precipitation, and maximum and minimum July temperature on ant species richness at each elevational band. Results We found that patterns of local ant species richness differed among the three gradients we sampled. Ant species richness increased linearly with elevation along two transects and peaked at mid‐elevation along a third transect. This suggests that patterns of species richness based on data from single transects may not generalize to larger spatial scales. Cluster analysis of community similarity revealed a high‐elevation species assemblage largely distinct from that of lower elevations. Major changes in the identity of ant species present along elevational gradients tended to coincide with changes in the dominant vegetation. Regional species richness, defined here as the total number of unique species within an elevational band in all three gradients combined, tended to increase with increasing elevation. Available area decreased with increasing elevation. Area was therefore correlated negatively with ant species richness and did not explain elevational patterns of ant species richness in the Spring Mountains. Mean July maximum and minimum temperature, July precipitation and annual precipitation combined to explain 80% of the variation in ant species richness. Main conclusions Our results suggest that in arid ecosystems, species richness for some taxa may be highest at high elevations, where lower temperatures and higher precipitation may support higher levels of primary production and cause lower levels of physiological stress.     

Variation in floristic and trait composition along environmental gradients in the herb layer of temperate forests in the transition zone between Central and SE Europe

Species- and trait-environment linkages in forest plant communities continue to be a frequent topic in ecological research. We studied the dependence of floristic and functional trait composition on environmental factors, namely local soil properties, overstory characteristics, climatic parameters and other abiotic and biotic variables. The study area comprised 50 monitoring plots across Slovenia, belonging to the EU ICP Forests monitoring network. Vegetation was surveyed in accordance with harmonized protocols, and environmental variables were either measured or estimated during vegetation sampling. Significant predictors of species composition were identified by canonical correspondence analysis. Correlations between plant traits, i.e. plant growth habit, life form, flowering features and CSR signature, were examined with fourth-corner analysis and linear regressions. Our results show that variation in floristic composition was mainly explained by climatic parameters (mean annual temperature, mean annual precipitation), soil properties (pH) and tree layer-dependent light conditions. Trait composition was most closely related with tree layer characteristics, such as shade-casting ability (SCA, a proxy for light availability in the understory layer), tree species richness and tree species composition. Amongst soil properties, total nitrogen content and soil texture (proportion of clay) were most frequently correlated with different species traits or trait states. The CSR signature of herb communities was associated with tree layer SCA, soil pH and mean annual temperature. The floristic composition of the studied herb-layer vegetation depended on temperature and precipitation, which are likely to be influenced by ongoing climate change (warming and drying). Trait composition exhibited significant links to tree layer characteristics and soil conditions, which are in turn directly modified by forest management interventions.

     

锡林河流域草原群落植物多样性和初级生产力沿水热梯度变化的样带研究

用样带法研究了草原群落植物多样性和初级生产力沿海拔和水分梯度的变化,结果表明;在样带梯度上,物种丰富度、多样性和群落初级生产力与海拔高度、年降水量和土壤有机C及全N含量呈正相关,而与年平均气温和干燥度呈负相关。随着海拔高度的降低,降水量的减少,热量和干燥度的增加,以及土壤有机C和全N含量的降低,草原群落的物种丰富度、多样性和初级生产力逐渐降低。典型相关分析的结果揭示出,土壤有机C含量和干燥度是对草原群落物种丰富度和初级生产力具有更大的影响。同时,草地的利用方式和强度对群落植物多样性和生产力也具有较强的影响。     

锡林河流域草原群落植物多样性和初级生产力沿水热梯度变化的样带研究

 用样带法研究了草原群落植物多样性和初级生产力沿海拔和水分梯度的变化,结果表明;在样带梯度上,物种丰富度、多样性和群落初级生产力与海拔高度、年降水量和土壤有机C及全N含量呈正相关,而与年平均气温和干燥度呈负相关。随着海拔高度的降低,降水量的减少,热量和干燥度的增加,以及土壤有机C和全N含量的降低,草原群落的物种丰富度、多样性和初级生产力逐渐降低。典型相关分析的结果揭示出,土壤有机C含量和干燥度是对草原群落物种丰富度和初级生产力具有更大的影响。同时,草地的利用方式和强度对群落植物多样性和生产力也具有较强的影响。     

Phylogenetic diversity of macromycetes and woody plants along an elevational gradient in Eastern Mexico

Phylogenetic information provides insight into the ecological and evolutionary processes that organize species assemblages. We compared patterns of phylogenetic diversity among macromycete and woody plant communities along a steep elevational gradient in eastern Mexico to better understand the evolutionary processes that structure their communities. Macrofungi and trees were counted and identified in eight sites from 100 to 3500 m asl, and sequence data retrieved from GenBank for the same or closely related species were used to reconstruct their phylogenies. Patterns of species richness and phylogenetic diversity were similar for both macrofungi and trees, but macromycete richness and diversity peaked at mid‐elevations, whereas woody plant richness and diversity did not show significant trends with elevation. Phylogenetic similarity among sites was low for both groups and decreased as elevational distance between sites increased. Macromycete communities displayed phylogenetic overdispersion at low elevations and phylogenetic clustering at high elevations; the latter is consistent with environmental filtering at high elevation sites. Woody plants generally exhibited phylogenetic clustering, consistent with the potential importance of environmental filtering throughout the elevational gradient.     

Variation in the composition and structure of tropical savannas as a function of rainfall and soil texture along a large-scale climatic gradient in the Northern Territory, Australia

Abstract. Variation in structural and compositional attributes of tropical savannas are described in relation to variation in annual rainfall and soil texture along a subcontinental-scale gradient of rainfall in the wet-dry tropics of the Northern Territory, Australia. Rainfall varies along the gradient from over 1500 mm p.a. in the Darwin region ( c . 12° S) to less than 500 mm in the Tennant Creek region ( c . 18° S). Soils are patchy, and sands, loams and clays may occur in all major districts within the region. We utilized a large data set (1657 quadrats ° 291 woody species; with numerous measured and derived sample variables) covering an area of 0.5 million km². Correlations between floristic composition of woody species and environmental variables were assessed using DCA ordination and vector fitting of environmental variables. Vectors of annual rainfall and soil texture were highly correlated with variation in species composition. Multiple regression analyses incorporating linear and quadratic components of mean annual rainfall and topsoil clay content were performed on three structural attributes (tree height, tree cover, tree basal area) and two compositional attributes (woody species richness, deciduous tree species richness). Tree height declined with decreasing rainfall; cover, basal area, woody species richness and deciduous species richness all declined with decreasing rainfall and increasing soil clay content. Regression models accounted for between 17% and 45% of the variation in the data sets. Variation in other factors such as soil depth, landscape position and recent land-use practices (for which there were no data on an individual quadrat basis) are likely to have contributed to the large residual variation in the data set.     

Microsite and elevational influences on early forest regeneration after catastrophic windthrow

Abstract. We compared vegetation establishment in 25 treefall pits and mounds along a hillside elevational gradient in a fourth-year catastrophic windthrow in eastern North America. Plant communities differed greatly between pits and mounds, with pit microsites having significantly greater species richness, total biomass, and total tree stem density. Species richness in pits and on mounds decreased with increasing elevation from the bottom of the hillside, although the effect of elevation on mound species richness was less than that of elevation on pit species richness. Biomass of Erechtites hieraciifolia decreased significantly, while that of Betula alleghaniensis increased significantly with elevation. However, total biomass of both pit and mound microsites was unrelated to elevation. Total stem density decreased with elevation in pits, but was unaffected by elevation on mounds. This study shows that both small-scale (microsite) effects and intermediate-scale effects influence the re-establishment of plant communities within this catastrophic windthrow. Consideration of both microsite and position along intermediate-scale gradients may allow more precise prediction of plant community composition and dynamics in recovery of disturbed areas.     

锡林河流域草原群落植物多样性和初级生产力沿水热梯度变化的样带研究

 用样带法研究了草原群落植物多样性和初级生产力沿海拔和水分梯度的变化,结果表明;在样带梯度上,物种丰富度、多样性和群落初级生产力与海拔高度、年降水量和土壤有机C及全N含量呈正相关,而与年平均气温和干燥度呈负相关。随着海拔高度的降低,降水量的减少,热量和干燥度的增加,以及土壤有机C和全N含量的降低,草原群落的物种丰富度、多样性和初级生产力逐渐降低。典型相关分析的结果揭示出,土壤有机C含量和干燥度是对草原群落物种丰富度和初级生产力具有更大的影响。同时,草地的利用方式和强度对群落植物多样性和生产力也具有较强的影响。     

新疆天山南坡中段种子植物区系垂直分布格局分析

对植物多样性垂直分布格局及其维持机制的研究可以有效揭示植物物种多样性分布特征及其环境影响因子。本文通过野外调查、查阅标本并结合相关文献资料,对天山南坡中段种子植物区系沿海拔梯度的分布格局进行了系统研究。结果显示,在大区域尺度上,科属种的物种丰富度随海拔升高均呈先增加后减少的趋势,且最高值出现在中低海拔1900~2000 m处;不同生活型植物沿海拔梯度的变化格局有所不同,其中,乔木、一年生草本、藤本及寄生植物表现出随海拔升高物种丰富度逐渐降低的趋势,灌木、多年生草本及二年生草本植物物种丰富度则呈先增加后减少的变化趋势;从植物区系地理成分来看,世界分布所占的比重沿海拔梯度升高呈先增加后减少的趋势;温带地理成分所占的比重沿海拔梯度升高呈缓慢上升趋势;古地中海地理成分所占的比重沿海拔梯度升高呈先增加后减少然后再增加的变化趋势;热带地理成分所占的比重沿海拔升高呈逐渐下降的趋势;东亚地理成分所占的比重沿海拔梯度升高呈先增加后减少然后再增加的变化趋势。对该分布格局与当地干旱的气候条件及海拔梯度上热量和水分条件的变化相适应。     

Trait variation and functional diversity maintenance of understory herbaceous species coexisting along an elevational gradient in Yulong Mountain,Southwest China

Characterizing trait variation across different ecological scales in plant communities has been viewed as a way to gain insights into the mechanisms driving species coexistence. However, little is known about how changes in intraspecific and interspecific traits across sites influence species richness and community assembly, especially in understory herbaceous communities. Here we partitioned the variance of four functional traits (maximum height, leaf thickness, leaf area and specific leaf area) across four nested biological scales: individual, species, plot, and elevation to quantify the scale-dependent distributions of understory herbaceous trait variance. We also integrated the comparison of the trait variance ratios to null models to investigate the effects of different ecological processes on community assembly and functional diversity along a 1200-m elevational gradient in Yulong Mountain. We found interspecific trait variation was the main trait variation component for leaf traits, although intraspecific trait variation ranged from 10% to 28% of total variation. In particular, maximum height exhibited high plasticity, and intraspecific variation accounted for 44% of the total variation. Despite the fact that species composition varied across elevation and species richness decreased dramatically along the elevational gradient, there was little variance at our largest (elevation) scale in leaf traits and functional diversity remained constant along the elevational gradient, indicating that traits responded to smaller scale influences. External filtering was only observed at high elevations. However, strong internal filtering was detected along the entire elevational gradient in understory herbaceous communities, possibly due to competition. Our results provide evidence that species coexistence in understory herbaceous communities might be structured by differential niche-assembled processes. This approach--integrating different biological scales of trait variation--may provide a better understanding of the mechanisms involved in the structure of communities.     

Elevation‐richness pattern of vascular plants in wadis of the arid mountain Gebel Elba,Egypt

Mountains provide a unique opportunity to study drivers of species richness across relatively short elevation gradients. However, few studies have reported elevational patterns for arid mountains. We studied elevation‐richness pattern along an elevational gradient at the arid mountain Gebel Elba, south‐east of Egypt, expecting a unimodal richness pattern. We sampled 133 vegetation plots (10 × 10 m) in four wadis along an elevational gradient from 130 to 680 m which represents the transition from desert to mountain wadi systems. We used generalised additive models to describe the relationship between elevation and plant species richness. We found a strong increase in species richness and Shannon diversity at low elevations followed by a plateau at mid‐ to high elevations. When we analysed each tributary as a single gradient, no pattern was found. The analysed elevational gradient seems to be a major stress gradient in terms of temperature and water availability, exhibiting a trend of increasing species richness that changes to a plateau pattern; a pattern rarely observed for wadi systems in arid mountains. We discuss the observed pattern with the climatic stress hypothesis and the environmental heterogeneity hypothesis as possible explanations for the pattern.     

Climate and vegetation structure determine plant diversity in Quercus ilex woodlands along an aridity and human-use gradient in Northern Algeria

We studied the influence of environmental factors relating to climate, soil and vegetation cover on total species richness, species richness of different life-forms and species composition of plant communities occurring in Quercus ilex woodlands, across a 450-km long transect in Northern Algeria constituting a gradient of aridity and human use. We sampled vegetation and collected environmental data in 81 10 m × 10 m plots in five zones representing the largest Q. ilex woodlands throughout the study area, analysing them within an a priori hypothesis framework with the use of Path Analysis. Changes in plant diversity were mainly influenced by environmental factors related to precipitation and temperature regimes, as well as by total plant cover. In particular, changes in species composition were determined by factors associated with the temperature regime through their influence on both woody and annual herbaceous plant richness, and by factors related to the precipitation regime through their influence on perennial herbaceous plant richness, likely due to the differential tolerances of these functional groups to cold and water stress. Our results emphasize the importance of differences in environmental adaptability of the most important life-forms with regard to explaining compositional change (beta diversity) along aridity gradients, and the mediator role of total plant cover in relation to the effects of soil conditions on plant diversity.     

Patterns of an elevational gradient affecting moths across the South Korean mountains: effects of geometric constraints,plants, and climate

We investigated elevational richness patterns of three moth groups (Erebidae, Geometridae, and Noctuidae) along four elevational gradients located on one northern and three southern mountains in South Korea, as well as the effects of plants and climatic factors on the diversity patterns of moths. Moths were collected with an ultraviolet light trap at 32 sites from May through October, 2013. Plant species richness and mean temperatures for January and June were acquired. Observed and estimated moth species richness was calculated and the diversity patterns with null models were compared. Species richness along four elevational gradients peaked at mid-elevations, whereas deviations occurred at elevations below mid-peak in the southern mountains and elevations higher than mid-peak on the northern mountain. Species richness curves of three moth groups also peaked at mid-elevations throughout South Korea. However, the species richness curves for Erebidae were positively skewed, indicating that a preference for lowlands, whereas curves of the Geometridae were negatively skewed, indicating a preference for highlands. The mid-peak diversity pattern between plants and moths on the Korean mountains showed an elevational breadth that overlapped between 800 and 900 m. Multiple regression analysis revealed that plant species richness and January mean temperature significantly influenced moth species richness and abundance. The rapid increase in mean annual temperature in the Korean peninsula and the unimodal elevational gradients of moths across the country suggest that an uphill shift in peak optimum elevation and changes in the highest peak of the curve will occur in the future.     

Phylogenetic structure of angiosperm trees in local forest communities along latitudinal and elevational gradients in eastern North America

Latitudinal and elevational gradients both represent thermal gradients. Assessing the consistency of the relationships between phylogenetic structure and climate between latitudinal and elevational gradients can provide insight into the mechanisms driving assembly of species from regional pools into local assemblages. The aim of this study is to compare patterns of phylogenetic structure measures for angiosperm tree species between latitudinal and elevational gradients, using a dataset of angiosperm tree species in 14 092 forest plots in eastern North America. We assessed whether these two gradients produce similar relationships between climate and phylogenetic structure, hypothesizing that they should differ in magnitude but not direction. We used correlation and regression analyses to assess the relation of measures of phylogenetic structure to elevation, latitude and climatic variables, which included minimum temperature, temperature seasonality, annual precipitation and precipitation seasonality. We found that 1) phylogenetic relatedness of angiosperm trees increases with decreasing temperature along both latitudinal and elevational gradients but the relationship between phylogenetic relatedness and temperature is steeper for elevational gradients than for latitudinal gradients; 2) the tip-weighted metric of phylogenetic relatedness (nearest taxon index) is more strongly correlated with climatic variables than the basal-weighted metric of phylogenetic relatedness (net relatedness index); 3) winter cold temperature exerts a stronger effect on community assembly of angiosperm trees than does temperature seasonality. These results suggest that winter cold temperature, rather than temperature seasonality, drives phylogenetic structure of plants in local forest communities, and that species distributions along elevational gradients are more in equilibrium with temperature, compared with those along latitudinal gradients.     

Distribution of amphibians along an elevation gradient in the Eastern Himalaya,india

Distribution of biodiversity along the elevation gradient have been a subject of curiosity and a much argued topic in macroecology. Despite considerable attention, there is a lack of consensus on the pattern and the causal factors across regions and taxa. We studied amphibian distribution along the elevational gradient in Sikkim, Eastern Himalaya, part of a globally significant biodiversity hotspot. We conducted intensive field studies covering 300–4600 m elevation using Visual Encounter Survey and Night Stream Survey methods. We examined the effects of both spatial factors (area and mid-domain effect) and environmental variables (temperature, precipitation, moisture, potential evapotranspiration and actual evapotranspiration) on the distribution of amphibians along the elevational gradient. We recorded 25 species and 1368 individuals of amphibians after 1236 man-hours of visual encounter survey and 27 km night stream survey. Species richness of total amphibians and their sub groups (endemic, non-endemic, large-range and small-range) followed unimodal pattern showing a peak at middle elevation but with slight shift towards higher elevation for endemic species. Various environmental variables, especially actual evapotranspiration and mean annual precipitation, explained the elevational distribution trend of amphibians in the Eastern Himalaya. Spatial factors played no significant role in shaping the pattern of amphibian distribution (except endemics and large-range species showing fit to mid-domain effect). Local communities of the study area extract amphibians for food and medicine, especially from the diverse mid elevation zone, which should be closely monitored and curbed by the wildlife authorities.     

Constraints on trait combinations explain climatic drivers of biodiversity: the importance of trait covariance in community assembly

Trade‐offs maintain diversity and structure communities along environmental gradients. Theory indicates that if covariance among functional traits sets a limit on the number of viable trait combinations in a given environment, then communities with strong multidimensional trait constraints should exhibit low species diversity. We tested this prediction in winter annual plant assemblages along an aridity gradient using multilevel structural equation modelling. Univariate and multivariate functional diversity measures were poorly explained by aridity, and were surprisingly poor predictors of community richness. By contrast, the covariance between maximum height and seed mass strengthened along the aridity gradient, and was strongly associated with richness declines. Community richness had a positive effect on local neighbourhood richness, indicating that climate effects on trait covariance indirectly influence diversity at local scales. We present clear empirical evidence that declines in species richness along gradients of environmental stress can be due to increasing constraints on multidimensional phenotypes.     

Elevational patterns in the vascular flora of a highly diverse region in southern Mexico

We examined general and family-specific patterns of vascular plant richness along a large elevational gradient (0?C3,670?m a.s.l.), assessed the continuity of these patterns and analysed their potential underlying causes in a high diversity region of the Sierra Madre del Sur, Oaxaca, Mexico. We used a vascular plant database constructed previously. The gradient was divided into 18 200-m elevation belts. To examine elevational patterns of richness, we used both observed and estimated (interpolated) species richness, as well as genus and family observed richness, for each belt. A generalised linear model (GLM) was used to assess the effect of altitude on area-corrected species richness (standard area?=?100?km²), and a numerical classification of the elevational belts based on species richness was performed. Overall, richness at the three taxonomic levels decreased with elevation, but some individual families departed from this pattern. A sharp drop in species richness was observed at 1,800?m, and the dendrogram separated two elevational floristic groups at this elevation. The GLM revealed a significant negative effect of elevation on species richness. Despite this overall decreasing pattern for vascular plants along this extensive gradient, an examination of some family-specific patterns revealed the existence of other elevation?Cdiversity relationships, indicating taxon-specific responses to elevation. The most noticeable discontinuity in species richness, at ca. 1,800?m, is likely related to a critical temperature isocline.