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Background: Tropical montane forests are important reservoirs of carbon and biodiversity but are threatened by deforestation and climate change. It is important to understand how forest structure and aboveground biomass change along gradients of elevation and succession. Questions: What are the interactive effect of elevation and two stages of succession on forest structure parameters? Studied species: Tree communities. Study site and dates: Cofre de Perote, Veracruz, Mexico. August to December 2015. Methods: We studied four sites along an elevational gradient (500, 1,500, 2,500, and 3,500 m). At each elevation and each forest type, we established five 20 × 20 m plots (n = 40 plots). Within each plot, we measured stem density, mean diameter at breast height (dbh), and tree height and derived basal area and aboveground biomass (AGB). Results: AGB peaked at 2,500 m and was significantly related to elevation and succession, with higher values in old-growth forests than in secondary forests at higher altitudes. Lower values of mean dbh and basal area were found at higher elevations. At the lowest elevation, both successional stages had the same values of stem density and AGB. At both lower elevations, secondary forests had higher values of dbh and basal area. There were high biomass stocks in the old-growth forest at 2,500 and 3,500 m. Conclusions: Old-growth forests at higher elevations are threatened by deforestation, consequently these remaining fragments must be preserved because of their storage capacity for biomass and their ability to mitigate climate change.

AimsUnderstanding variation and coordination of leaf traits at multiscales along elevational gradients can help predict the likely responses of dominant species to climate change. We seek to determine the extent to which variation in leaf stomatal, anatomical and morphological traits is associated with environmental factors, and whether ecological strategies of Cyclobalanopsis species shift with elevations.MethodsIn a tropical forest landscape in Jianfengling, South China, we determined leaf traits related to stomata, anatomy and morphology of six evergreen oak species (Cyclobalanopsis bambusaefolia, C. hui, C. patelliformis, C. fleuryi, C. tiaoloshanica and C. phanera) along a long elevational gradient (400–1400 m above sea level).Important FindingsWe found that stomatal density and stomatal pore index increased, whereas spongy mesophyll thickness to leaf thickness ratios decreased, significantly with elevation. The leaf area and leaf dry matter content increased and decreased, respectively, with elevation. Variations in stomatal, anatomical and morphological traits were mainly correlated to the mean annual temperature, mean annual sum precipitation and soil pH. At low and high elevations, the oak species exhibited strong stress tolerance combined with competition strategy, while they shifted toward more clearly the competitive strategy at intermediate elevations. And the changes in soil phosphorus concentration and soil pH along the elevation may drive the shift of ecological strategy. The results showed that the dominant oak species in tropical forests respond to environmental change by modulating traits at multiple levels, from that of the individual cell, through tissue and up to the whole leaf scale.

Aims Biodiversity patterns along elevational gradients have been well documented. Yet, the variations of biodiversity patterns along elevations and their underlying mechanisms are still unclear. Integrating multiple facets of biodiversity provides novel insights into the mechanisms for driving community assembly. In this study, species abundance information was incorporated into taxonomic and phylogenetic diversity to reveal the ecological and evolutionary forces of plant community assembly along an elevational gradient in subtropical forests. Methods We selected 17 woody plant plots along an elevational gradient from 270 to 1470 m in eastern China’s subtropical forests. Both presence-based and abundance-based measures of angiosperm species were used to quantify taxonomic alpha diversity, phylogenetic alpha diversity, phylogenetic relatedness, as well as taxonomic and phylogenetic dissimilarity among these plots. And the relations between these measures and climatic and topographic variables were analyzed. Important Findings For both abundance-weighted and unweighted measures, we observed an overall increasing pattern for taxonomic alpha diversity along elevation, and distance-decay trends of taxonomic and phylogenetic similarity with increased elevational distances. However, there were disparity patterns of phylogenetic alpha diversity between abundance-weighted and unweighted measures. For phylogenetic structure, there was no significant trend along elevation. Both topographical and microclimatic variables were main drivers of diversity patterns and phylogenetic structure. Compared with unweighted measures, abundance-weighted measures were strongly related with the slope and stand basal area. Overall, our results prove that deterministic processes mediated by local species abundance imprint on plant community composition along the elevational gradient.

Premise One of the best-documented ecological responses to climate warming involves temporal shifts of phenological events. However, we lack an understanding of how phenological responses to climate change vary among populations of the same species. Such variability has the potential to affect flowering synchrony among populations and hence the potential for gene flow. Methods To test whether an earlier start of the growing season affects the potential for gene flow among populations, we quantified the distributions of flowering times of two spring-flowering plants (Trillium erectum and Erythronium americanum) over 6 years along an elevational gradient. We developed a novel model-based metric of potential gene flow between pairs of populations to quantify the potential for pollen-mediated gene flow based on flowering phenology. Results Earlier onset of spring led to greater separation of peak flowering dates across the elevational gradient for both species investigated, but was only associated with a reduction in potential gene flow in T. erectum, not E. americanum. Conclusions Our study suggests that climate change could decrease gene flow via phenological separation among populations along climatic gradients. We also provide a novel method for quantifying potential pollen-mediated gene flow using data on flowering phenology, based on a quantitative, more biologically interpretable model than other available metrics.

The influence of mycorrhizal symbiosis on ecosystem processes depends on the mycorrhizal type and status of plants. Early research hypothesized that the proportion of arbuscular mycorrhizal (AM) species decreases and of ectomycorrhizal (ECM) and ericoid mycorrhizal (ERM) species increases along increasing elevations and latitudes. However, there is very scarce information about this pattern along elevation gradients. We aimed to test this hypothesis and to describe the trends in plant mycorrhizal status by examining the Pyrenean mountain range (from 400 to 3400 m asl). The distribution of plant mycorrhizal types: AM, ECM, ERM, and non-mycorrhizal (NM) and status (obligately, OM, or facultatively, FM mycorrhizal plants, FM) were identified based on the Pyrenean Floristic Atlas and analyzed for climatic and edaphic drivers. The proportion of AM plants decreased slightly with elevation, while ECM species peaked at 1000 m asl. The proportion of ERM and NM plant species rose with increasing elevation. The proportion of FM species increased, and OM species decreased with increasing elevation. The change of AM and ECM species, and OM and FM species, along the elevational gradient, corresponds broadly to changes along the latitudinal gradient, driven by a combination of climatic and edaphic factors. Differently, the elevational occurrence of NM plant species is mainly driven only by climatic factors (low temperature) and that of ERM species by only edaphic factors (low pH). Large-scale macroecological studies (≥ 50 km grid cell) well reflect the effects of climate on the distribution of plant mycorrhizal traits, but local data (≤ 1 km grid cell) are needed to understand the effects of soil conditions and land use.

Alpine treelines are thought to be controlled by low temperature, which affects tree physiology and limits growth. Irrespective of carbon and nutrient limitations are physiological mechanisms affecting the formation of alpine treelines still needs to be defined. We measured the rates of tree growth (basal area increment, BAI), nutrient concentrations in leaves and roots, foliar concentration of nonstructural carbohydrates (NSCs), and gas exchange in Pinus taiwanensis at five elevations (1200, 1400, 1600, 1800, and 2000 m) in the Wuyi Mountains, China. Leaves and roots were sampled twice (summer and winter). The soil nitrogen (N) and phosphorus (P) concentrations and BAI were measured during the summer. We analyzed the foliar traits in summer and winter. The N:P ratio was also analyzed. BAI decreased significantly as elevation increased, accompanied by increases in foliar NSC, N, and P concentrations in both summer and winter. The root P concentration increased with elevation in summer, but the foliar N:P ratio and root N and P concentrations were not affected by elevation in winter. Foliar photosynthesis and respiration did not change in winter, but increased in summer as elevation increased. These results suggest that C and nutrients may not be limiting resources in P. taiwanensis at this alpine treeline site, which instead may be controlled by temperature. P. taiwanensis at alpine treelines accumulates C and nutrient to increase its rates of biochemical reactions at low temperatures.

Models of ecological responses to climate warming predict species’ migration towards higher latitudes or elevations. However, models often neglect nonclimatic factors, such as herbivory, which could slow down or prevent geographic range expansion. A previous study in Mont Mégantic National Park (Quebec) found that in one year (2016), browsing by white-tailed deer on Trillium erectum L. was substantially higher at high elevations than low elevations. Under the hypothesis that deer herbivory could limit the upper elevational range expansion of T. erectum, here we ask (i) whether herbivory increased with elevation during two additional years (2017 and 2018), (ii) whether the rate of deer visitation increases with elevation, and (iii) whether the effect of herbivory on relative growth rates increases with elevation. Contrary to the earlier study, we did not find a significant trend of herbivory with elevation, although there was a weak positive relationship between deer visitation and elevation. We found a strong negative impact of browsing on relative growth rates, but the magnitude of this effect did not vary with elevation. Our results thus do not support the hypothesis that herbivory limits the range of T. erectum at high elevation, but herbivory could have a negative impact on populations in general if the browsing rate remains high.

Key messagePhloem cell production was less influenced by environmental factors than xylem cell production. The moment of maximum number of conducting phloem cells occurred at the end of the growing season.AbstractThe understanding of the seasonality of phloem production, its dependence on climatic factors and potential trade-offs with xylem cell production is still limited. This study determined key tree-ring phenological events and examined the dynamics of phloem and xylem cell production of Norway Spruce (Picea abies(L.) Karst) by sampling microcores during the growing seasons 2014 and 2015 along an elevational gradient (450 m, 750 m, 1250 m a.s.l.) in south-western Germany. The onset of phloem formation preceded xylem formation at each elevation by approximately 2 weeks, while cessation showed no clear differences between the stands. Maximum rates of xylem and phloem cell production were observed around the summer solstice, independent of elevation. No linear pattern was found in the occurrence of phenological events along the elevational gradient. Phloem formation appeared to be less sensitive to environmental conditions since no difference was found in the number of produced sieve cells between the 2 years of study, whereas the ratio of xylem to phloem cells was significantly smaller in the year 2015 with summer drought. The total number of conducting, non-collapsed phloem cells did not culminate as expected at the time of the potential maximum assimilate production, but at the end of the growing season. Thus, interpretation of phloem formation should not be limited to the function of assimilate transport but should follow a more holistic view of structural–functional relationships of conductive tissues and tree physiological processes.

Ecologists have embraced phylogenetic measures of assemblage structure, in large part for the promise of better mechanistic inferences. However, phylogenetic structure is driven by a wide array of factors from local biotic interactions to biogeographical history, complicating the mechanistic interpretation of a pattern. This may be particularly problematic along elevational gradients, where rapidly changing physical and biological conditions overlap with geological and biogeographical history, potentially producing complex patterns of phylogenetic dispersion (relatedness). We focus on the longest elevational gradient of vegetation in the world (i.e. c. 6000 m in Nepal) to explore patterns of phylogenetic dispersion for angiosperms (flowering plants) along this elevational gradient. We used the net relatedness index to quantify phylogenetic dispersion for each elevational band of 100 m. We found a zig-zag pattern of phylogenetic dispersion along this elevational gradient. With increasing elevation, the phylogenetic relatedness of species decreased for the elevational segment between 0 and c. 2100 m, increased for the elevational segment between 2100 and c. 4200 m, and decreased for the elevational segment above c. 4200 m. We consider this pattern to be a result of the interaction of geophysical (e.g. plate tectonics) and eco-evolutionary processes (e.g. niche conservatism and trait convergence). We speculate on the mechanisms that might have generated this zig-zag pattern of phylogenetic dispersion.

The family Araceae (aroids) represents an ecologically important and diverse group of plants in Panama, represented by 25 genera, 615 species, of which 277 (45%) are considered endemic. The aim of this study is to analyse the diversity and distributional patterns of aroids along an elevation gradient in the species-rich forests of Darién, Panama. We confined our study to three study sites, selected across gradients of elevation (ranges): 100–300, 500–700 and 1100–1300 m. We recorded 3187 specimens, of which 397 were terrestrials, 637 epiphytes and 2153 nomadic vines, distributed in 10 genera and 61 species. Our study shows that the most diverse areas were those between 500 and 700 m and the highest abundance were measured at 1100–1300 m. The epiphytic aroids displayed greater species richness and abundance at 1100–1300 m; the nomadic vines had greater richness between 500 and 700 m and greater abundance from 100 to 300 m. Similarly, terrestrial aroids showed greater richness at 500–700 m, and exhibited abundance values similar to that of the epiphytes. We measured a high degree of aroid species turnover along the elevation gradient and some genera and species (many being endemic) appeared strongly associated with sites at specific elevations.

Plant functional traits determine plant performance and have therefore the potential to shape and predict species distributions along environmental gradients. This study analyses how traits affect tree species distribution along an elevational gradient in the Himalayas, Nepal. We addressed three questions: (a) what plant strategies can be distinguished among tree species? (b) how are plant traits and strategies associated with elevation? and (c) what plant traits are the best predictors of species positions along elevational gradient? We quantified for 31 tree species a set of 39 plant traits related to resource uptake, use and conservation. We analysed how traits cluster into separate functions using a cluster analysis, and how traits and clusters associate into distinct plant strategies using a principal component analysis. The cluster analysis showed five clusters of traits, reflecting (a) efficiency in vertical expansion, (b) efficiency in horizontal expansion, (c) efficiency in metabolism, (d) physical defence and (e) tree functional groups (conifers vs. broadleaf species). The first PCA axis reflects trade-offs in traits and clusters linked to elevation: highland species had trait values that increase safety against freezing induced cavitation, high solar radiation and strong wind, and that increase resource conservation. In contrast, lowland species had trait values that increase efficiency of resource acquisition, metabolism and expansion. Additionally, a bivariate analysis showed that the first PCA axis is more strongly related to elevation than the individual traits, indicating that the combination of traits is more important than the individual traits. An all subsets regression analysis showed that a small set of traits best explain species distribution: highland species had smaller size (low basal area), safer hydraulics (low conduit diameter) and lower leaf and branch display efficiency (low leaf area per xylem area, specific branch length) that increase persistence under harsh conditions. Remarkably, leaf traits were poor predictors of species' elevational positions. Synthesis. Multiple trade-offs in plant size, hydraulics and light competitiveness shape species distribution along the elevational gradient. Along this extreme environmental gradient, stem and branch traits that integrate multiple plant organs and functions are better predictors of species' elevational distributions than leaf traits.

Aims Persistence plays a key role in both plant population and community dynamics as it allows withstanding temporarily habitat conditions unsuitable for growth and reproduction. Plants can exploit three different strategies to persist in situ (building soil seed banks, increasing adult longevity and/or clonal reproduction), the dominance of which in a community might vary along environmental gradients. Yet, their relative role in plant persistence has never been investigated. Location The Bavarian Alps, Germany. Methods We collected data on seed soil persistence, adult longevity and clonality for 290 species occurring in 18 grasslands located along an elevational gradient of 1,000 metres and examined their contribution to persistence in a community. Linear models were used to estimate the relationship between elevation and these persistence strategies. Results We found that dominance of a certain persistence strategy varied depending on environmental variability. Specifically, persistence in lowlands was mainly achieved by persistent and dense soil seed banks along with extended clonal growth (larger spread distances and higher number of offspring). Contrastingly, the main persistence strategy in the alpine communities was increased adult longevity. Conclusions The changes in relative contribution of each strategy to community persistence along the elevational gradient are interrelated suggesting a trade-off among them. We conclude that this trade-off plays an important role in species co-existence and community assembly, and might be useful to understand vegetation dynamics under ongoing climate change and improve restoration efforts of upland ecosystems.

The southern Appalachian Mountains in the United States are heavily forested with diverse forest types and vegetation structures and is generally considered a biodiversity hotspot. Fungal sporocarp investigations in this region are not new, but multi-year interseasonal investigations into sporocarp community patterns are rare. Using a 4-year (2014–2017) repeated monthly macrofungal sampling dataset (May–October) across an elevational gradient (associated with vegetation structure), we queried community, seasonal, and guild community ecological patterns. In doing so, we (1) demonstrate a temporal disconnect between saprobic and ectomycorrhizal taxa, (2) describe increased community variability across the growing season, and (3) explore individual taxa occurrences across seasons and examine co-occurrence patterns between taxa and guilds. Further, we explore congruence between sporocarp and metabarcoding fungal datasets and advocate the utility of both sampling schemes.

Understanding natural community assembly along elevational gradients has long attracted the attention of ecologists and botanists. Here, we study a tropical local-scale elevational gradient at a dissected mountainous terrain to understand if drivers of tree community variation and assembly patterns are similar to those reported for greater spatial distances and elevational gradients in the Atlantic Forest region. We inventoried trees with Diameter at Breast Height (DBH) ≥5.0 cm in 154 plots (10 × 10 m; 1.54 ha) systematically distributed along a local-scale (

Background: Treeline ecotones represent environmental boundaries that fluctuate in space and time and thus induce changes in plant taxonomic and functional diversity. Aims: To study changes through time in taxonomic and functional plant diversity patterns along the treeline ecotone. Methods: In 2002, vegetation was sampled along a gradient from upper montane forest to the treeline–alpine transition in the South Ural Mountains, Russia. In 2014, vegetation was resampled and plant functional traits were collected. We studied spatial and temporal changes in plant species composition, functional composition and functional diversity. Results: Species composition and diversity changed along the elevational gradient. The functional composition in height, leaf area, specific leaf area and leaf nitrogen content decreased with elevation, whereas functional composition of leaf carbon content increased. We found a temporal shift towards shorter plants with smaller leaves in treeline sites. Functional richness varied in several traits along the elevational gradient, while functional dispersion showed a trend towards increased functional dispersion in height, specific leaf area and leaf nitrogen in the treeline–tundra transition. Conclusions: Tree encroachment across the treeline ecotone has resulted in a shift in plant species relative abundances and functional diversity, possibly affecting plant community assembly patterns.

A general relationship between the nitrogen (N) and phosphorus (P) content of all plant organs (e.g. leaf, stem, and root) is hypothesized to exist according to whole-plant economics spectrum (PES) theory, but the evidence supporting these expected patterns remains scarce. We measured the N and P content of the leaves, twigs and fine roots of 64 species in three different forest communities along an elevational gradient (evergreen broad-leaved forest, 1319 m a.s.l., coniferous and broad-leaved mixed forest, 1697 m a.s.l., and deciduous forest, 1818 m a.s.l.) in the Wuyishan National Nature Reserve, southeastern China. The scaling relationship between the N and P content and the linear regression relationship between the N:P ratio and N and P content were analysed. The leaf N and P content was significantly higher at the high-elevation site than at the low- or middle-elevation sites (P < 0.001). The N and P content followed a power-law relationship with similar scaling slopes between organs. The N (common slope, 1.13) and P (common slope, 1.03) content isometrically covaried among leaves, twigs and roots. The scaling exponents of the N–P relationship were not significantly different from 1.0 in all organs, with a common slope of 1.08. The scaling constants of N–P decreased significantly (P < 0.05) from the highest value in fine roots (β = 1.25), followed by leaves (β = 1.17), to the lowest value in twigs (β = 0.88). Standardized major axis (SMA) analyses and comparisons of 95 % confidence intervals also showed that the numerical values of the scaling slopes and the scaling constants did not differ regardless of elevation. The N content, but not the P content, accounted for a large proportion of the variation in the N:P ratio in leaves (N:P and N: r2 = 0.31, F = 33.36, P < 0.001) and fine roots (N:P and N: r2 = 0.15, F = 10.65, P < 0.05). In contrast, the N:P ratio was significantly related to both the N and P content in the twigs (N:P and N: r2 = 0.20, F = 17.86, P < 0.001; N:P and P: r2 = 0.34, F = 35.03, P < 0.001, respectively). Our results indicate that different organs of subtropical woody plants share a similar isometric scaling relationship between their N and P content, providing partial support for the PES hypothesis. Moreover, the effects of the N and P content on the N:P ratio differ between metabolic organs (leaves and fine roots) and structural organs (twigs), elucidating the stoichiometric regulatory mechanism of different organs., We found the scaling exponents of the N-P relationship were not significantly different from 1.0 in all organs, with a common slope of 1.08. The numerical values of the scaling slopes and the scaling constants did not differ regardless of elevation. These results indicated the different organs of subtropical woody plants share a similar isometric scaling relationship between their N and P content. Moreover, the effects of the N and P content on the N:P ratio differ between metabolic organs (leaves and fine roots) and structural organs (twigs), elucidating the stoichiometric regulatory mechanism of different organs.

Efforts to develop mechanistic tree growth models are hindered by the uncertainty of whether and when tree growth responses to environmental factors are driven by carbon assimilation or by biophysical limitations of wood formation. In this study, we used multiannual weekly wood-formation monitoring of two conifer species (Larix decidua and Picea abies) along a 900 m elevational gradient in the Swiss Alps to assess the biophysical effect of temperature and water potential on wood formation. To this end, we developed a model that simulates the effect of water potential on turgor-driven cambial division, modulated by the effect of temperature on enzymatic activity. The model reproduced the observed phenology of tracheid production, as well as intra- and interannual tracheid production dynamics of both species along the elevational gradient, although interannual model performance was lower. We found that temperature alone explains the onset of tracheid production, yet water potential appears necessary to predict the ending and the total amount of tracheids produced annually. We conclude that intra-annual cambial activity is strongly constrained by both temperature and water potential at all elevations, independently of carbon assimilation. At the interannual scale, biophysical constraints likely interact with other factors.

1. Plant-fungal interactions are important for plant community assembly, but quantifying these relationships remains challenging. High throughput sequencing of fungal communities allows us to identify plant-fungal associations at a high level of resolution, but often fails to provide information on taxonomic and functional assignment of fungi. 2. We transplanted seeds of Pinus cembra across an elevational gradient (1850–2250 m a.s.l.) and identified environmental factors and known fungal associates important for seedling establishment and survival. We then applied null model tests to identify taxonomically unassigned fungi associated with pine recruitment. 3. Early seedling establishment was determined by abiotic environmental factors, while seedling survival was predominantly affected by biotic environmental factors (i.e., the abundance of a fungal pathogen known from literature and the distance to adult trees). Null model tests identified known mycorrhizal partners and a large number of unknown operational taxonomic units (OTUs) associated with seedling survival, including saprotrophic and pathogenic species. These results highlight that unknown fungal OTUs, which are usually discarded from analyses, could play a crucial role for plant survival. 4. Synthesis. We conclude that high throughput metabarcoding paired with null model tests, is a valuable approach for identifying hidden plant-fungal associations within large and complex DNA metabarcoding datasets. Such an approach can be an important tool in illuminating the black box of plant-microbe interactions, and thus understanding ecosystem dynamics.

The relationship between leaf and stem biomass as well as the relationship between leaf biomass and stem length and diameter are important to our understanding of a broad range of important plant scaling relationship because of their relationship to photosynthesis and thus growth. To understand how twig architecture (i.e., current year leaves, and stem diameter and length) affects stem diameter and length, and leaf number and biomass, we examined the twigs of 64 woody species collected from three forest types along an elevational gradient in the Wuyi Mountains, Jiangxi Province, China. We also compared the scaling relationships we observed with biomass allocation patterns reported at the whole tree level. Our results revealed isometric relationship between leaf and stem biomass on twigs despite differences in forest communities and despite changes in environmental factors along an elevational gradient. Across the 64 species, from twigs to individual trees, leaf biomass scaled approximately as the 2.0-power of stem diameter (but not for stem length or leaf number). These results help to identify a general rule that operates at two different levels of biological organization (twigs and whole trees). The scaling relationship between leaf biomass and stem diameter in twigs is insensitive to differences in species composition, elevation, or forest type. We speculate that this rule emerges because stem diameter serves as a proxy for the amount of resources supplied per unit cross section to developing leaves and for the flow of photosynthates from mature leaves to the rest of the plant body.

In the original publication of the article, under the discussion section, the following sentence “taxa to accumulate a larger fraction of leaf dry mass before the arrival of the rainy season (LmRS).” was separated from the previous sentence and published as two paragraphs.

Morphological variations in vegetative and reproductive organs in the Solidago virgaurea complex were examined for eight elevations between 1600 and 2400 m a.s.l. in Japan. The rosette diameter and stem height were lower at higher elevations. The stem diameter at any stem height was greater at higher elevations, suggesting that the S. virgaurea complex increases mechanical stiffness against strong wind at high elevations. The number of flower heads at any stem height was less at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Leaf nitrogen concentration did not change along the elevational gradient. Leaf mass per area (LMA) tended to decrease with increasing elevation, except for 2400 m a.s.l. The decrease of LMA would contribute to maintaining a positive carbon balance at high elevations. The number of involucral rays of flower heads was mostly four at low elevations (1600–1900 m a.s.l.) and three at high elevations (2000–2400 m a.s.l.). The number of involucral scales and diameter of flower heads were greater at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Therefore, the S . virgaurea complex is suggested to adapt to high elevations that have cool temperature, a short growing season and strong wind conditions by changing its vegetative and reproductive traits.

Questions Why does bryophyte richness increase along the elevational gradient? Even though a number of studies have documented the peculiar positive (or hump-shaped) relationship between species richness and elevation in bryophytes, it is still unclear which underlying mechanisms cause the pattern. Location Norway spruce forests, Italian Alps, South Tyrol. Methods Eight gradients from 900 to 1900 m a.s.l. and three different substrata (forest floor, deadwood, tree trunks) were examined. Three responses from the bryophyte communities were analysed: species richness of mosses and liverworts, functional diversity (considering the morphological characteristics of species) and β-diversity (separating the two components: richness difference and species turnover). Results On deadwood and tree trunks a quadratic relationship was found between bryophyte richness and elevation, but not on the forest floor. On all three substrata, the moss assemblages along the elevational gradient were dominated by the turnover process and not by the richness component of β-diversity. In liverworts, the two components of β-diversity were equally important. Temperature was the most important predictor of bryophyte richness, whereas model selection suggested that temperature, solar radiation and rainfall had equal effects on functional diversity. Conclusions The substrata affect the response of bryophytes to the elevational gradient. The bryophyte assemblages inhabiting the forest floor, being less subject to climatic variability than deadwood and tree trunks, could be less affected by the temperature increase where climate change is occurring.

International audience

Questions Have species expanded their ranges upward in elevation? Have α- and β-diversity changed over time? Have species richness changes along the gradient shown distributional patterns? Have community compositions changed over time, and if so, which plant families are responsible for variation? Do herbaceous changes correspond to increased warming, overstorey shifts and disturbance events at each site? Location Long-term Ecological Research (LTER) sites near Niwot Ridge, CO, US. Methods We surveyed four herbaceous plant communities along an elevational gradient for species composition, diversity and frequency. Our results were compared to those found in 1981 and 1996 in the same plots to determine long-term community change at each site and along the elevational gradient. We evaluated changes in elevational species range expansion, community diversity, and composition. We related herbaceous change to tree data and site-specific literature on climate and disturbance to analyze change patterns and drivers. Results Our investigation showed the upward range expansion of eight species. Alpha-diversity changes were site-specific, while species richness changes along the gradient did not exhibit distinctive patterns. Each community changed significantly (P

This study explores soil nutrient cycling processes and microbial properties for two contrasting vegetation types along an elevational gradient in subarctic tundra to improve our understanding of h ...

Question Is clade age positively correlated with minimum temperature in angiosperm woody assemblages along elevational thermal gradients, as predicted by the phylogenetic niche conservatism hypothesis and observed along latitudinal gradients? Location South America. Methods I assembled one latitudinal gradient and one elevational gradient of angiosperm woody plant assemblages in forest plots, both of which started at equatorial humid forests at low elevations. The latitudinal gradient comprised 37 plots and the elevational gradient included 34 forest plots. Each plot is 0.1 ha. Correlation analysis was used to determine relationships among taxonomic richness, mean clade age (measured as mean family age of each forest plot), latitude, elevation and minimum temperature (measured as mean temperature of the coldest month). Results Woody plant species richness strongly decreases with increasing latitude and elevation on the two gradients. Mean clade age is positively correlated with minimum temperature for the latitudinal gradient but is negatively correlated with minimum temperature for the elevational gradient. Conclusion The result of this study based on the latitudinal gradient supports the prediction of the phylogenetic niche conservatism hypothesis for the relationship between clade age and temperature, whereas the result based on the elevational gradient is contrary to the prediction of this hypothesis. The contrasting patterns found in the present study for the clade age-minimum temperature relationship along the latitudinal vs elevational gradients suggest that more studies are needed in order to determine how general is the positive relationship between clade age and temperature predicted by the PNC along both latitudinal and elevational gradients across the globe.

There is currently enormous interest in how morphological and physiological responses of herbaceous plants may be affected by changing elevational gradient. Mountain regions provide an excellent opportunity to understand how closely related species may adapt to the conditions that rapidly change with elevation. We investigated the morphological and physiological responses of two Himalayan alpine gingers (Roscoea alpina and R. purpurea) along two different vertical transects of 400 m, R. purpurea between 2,174–2,574 m a.s.l and R. alpina between 2,675–3,079 m a.s.l. We measured the variables of plant height, leaf length, leaf area, specific leaf area, and stomata density at five plots, along the vertical transect at an elevational gap of ca. 100 m. Results revealed that with increased elevation plant height, and leaf area decreased while stomata density increased, whereas changes in specific leaf area, were not correlated with the elevation. Our results reveal that these alpine gingers undergo local adaptation by modifying their plant height, leaf area and stomata density in response to the varying selection pressure associated with the elevational gradient. Thus, the findings of this research provide valuable information on how a narrow range of elevational gradient affects the herbaceous plants at the alpine habitat of the Himalayas.

It has long been known that the species richness along an elevational gradient shows either a monotonic decrease or a hump-shaped pattern. The distribution of polypores at six altitudes (800 m, 1 000 m, 1 200 m, 1 400 m, 1 600 m and 1 800 m) was analyzed based on 10 yr of field data from Changbaishan Nature Reserve, Northeastern China. The polypore richness decreased from 153 to 8 species with increasing elevation, showing a monotonic decrease pattern. Moreover, the proportions of white- and brown-rot-causing polypores generally decreased and increased, respectively, along the elevational gradient from an altitude of 800 m–1 600 m, but the highest altitude site exclusively with Betula ermanii had the highest and lowest proportions of white- and brown-rot polypores, respectively. These patterns might be caused by changes in the forest type and in various abiotic factors associated with changes in different altitudes.

International audience; The variation in the leaf content of phenolic compounds has been related to the UV-B changes of the environment in which plants grow. In this context, we aimed to investigate: a) whether the seasonal and altitudinal changes in the content of phenolic compounds of Buxus sempervirens L. leaves and cuticles could be related to the natural fluctuations in UV-B levels and b) the possible use of specific phenolic compounds as biomarkers of ambient UV-B levels. To achieve these goals we sampled, every three months during one year, leaves of B. sempervirens along an altitudinal gradient. At the lowest and the highest altitudes, we also conducted a UV-exclusion experiment to discern whether the observed changes could be attributed to the natural variation in UV-B. Results show that total phenolic content of leaves was lower in June than in the other sampling dates, which suggests a leaf ontogenic rather than a UV-B effect on the leaf content of these compounds. Regarding the elevational gradient, the overall amount of phenolic acids and neolignan of entire leaves increased with altitude while the total amount of flavonoids in leaf cuticles decreased. However, the lack of a significant effect of our UV-exclusion treatment on the content of these compounds suggests that the observed variations along the altitudinal gradient would respond to other factors rather than to UV-B. Concomitantly, we did not find any phenolic compound in leaves or cuticles of B. sempervirens that could be considered as a biomarker of ambient UV-B levels. (c) 2013 Elsevier Masson SAS. All rights reserved.

The estimation of carbon density of high altitude forests was carried out at fi ve different sites along an elevational gradient from 1550 m to 3550 m in a part of Kedarnath Wildlife Sanctuary, which is one of the largest protected areas of the Garhwal Himalaya, India. Among the study sites the above ground biomass density (AGBD) ranged from 202.72 Mg·ha−1 (Site 5) to 718.75 Mg·ha−1 (Site 1) and below ground biomass density (BGBD) from 61.00 Mg·ha−1 (Site 5) to 203.04 Mg·ha−1 (Site 1). The total biomass density (TBD) also followed similar trend, where the lowest value (263.73 Mg·ha−1) was observed at Site 5 and the highest (921.79 Mg·ha−1) at Site 1. The total carbon density (TCD) ranged from 131.86 Mg·ha−1 (Site 5) to 460.89 Mg·ha−1 (Site 1), which indicates that the carbon density of forests reduces with increasing elevation.

The effects of warming on autumnal growth cessation and bud formation in trees remain ambiguous due to contrasting observations between a range of studies under controlled conditions and field experiments. High night temperature has been reported to advance growth cessation and bud formation in several tree species grown under controlled conditions. On the other hand, some recent field experiments have shown that autumn warming delays bud formation, although the temperature parameters that could account for this effect have not been identified. In addition, dioecious species have been shown to respond differently to environmental change, and differential warming effects on the sexes have received limited attention, even more so in relation to phenology. In a data set including three separate field experiments employing either experimental warming or an elevational gradient, we tested the effect of different temperature parameters on apical, vegetative bud formation and transitions between bud stages in female and male clones of Eurasian aspen (Populus tremula). Increased temperature was found to delay bud formation, and this process was best explained by maximum daily temperature. Males were significantly delayed compared with females in forming green closed buds, a process best explained by mean 24 h temperature. Bud maturation was best explained by mean daytime temperature, and buds matured significantly faster in males than in females, possibly explaining why females and males did not differ in terms of overall bud formation. In conclusion, our data show that delayed bud formation in Eurasian aspen during autumn can be attributed to the effect of high temperature, and this effect is in contrast to most of the evidence from studies of bud development in controlled environments.

Individual species are expected to shift their distributions in response to global climate change. Species within existing communities may respond to climate change individualistically, resulting in the formation of novel communities, or may instead shift as intact communities. We examined whether montane plant communities in the northeastern United States have shifted their elevational range as intact assemblages or individualistically in response to recent regional climatic and environmental change. We used non-metric multidimensional scaling (NMDS) to examine changes in plant community composition and species distributions using vegetation surveys repeated five times between 1964 and 2006 across an elevational gradient (549–1158 m) on Camels Hump Mountain, Vermont, USA, in conjunction with an analysis of local climate change. We found evidence that species elevational distributions and community compositions have shifted in response to a 0.49 °C per decade warming. These species responses were...

Accurate and non-destructive methods to determine individual leaf areas of plants are a useful tool in physiological and agronomic research. Determining an individual leaf area (LA) involves measurements of leaf length (L) and width (W), or some combinations of both parameters. Investigation was carried out in 2008 and 2009 to test whether a model could be developed to estimate leaf area of Bergenia purpurascens along an elevational gradient across a timberline ecotone, southeastern Tibet. A total of 786 leaves, 153–159 leaves for each 100-m elevation range, were measured in June 2008 for model construction. Coefficients of LA models incorporating both leaf dimensions (L and W) or W alone were independent of elevation, suggesting that a common model can be employed to estimate LA across the whole elevation range. A single-variable model using the leaf width (LA = 1.44W1.90), which was simpler, more convenient and also allowed reliable LA estimations, was developed. By applying this equation to another ind...

Understanding the spatial and temporal dynamics of species assemblages is a main challenge in ecology. The mechanisms that shape species assemblages and their temporal fluctuations along tropical elevational gradients are particularly poorly understood. Here, we examined the spatio-temporal dynamics of bird assemblages along an elevational gradient in Ecuador. We conducted bird point counts at three elevations (1000, 2000 and 3000 m) on 18 1-ha plots and repeated the sampling eight times over two years (216 hours in total). For each plot, we obtained data of monthly temperatures and precipitation and recorded the overall resource availability (i.e., the sum of flower, fruit, and invertebrate resources). As expected, bird richness decreased from low to high elevations. Moreover, we found a significant decrease in bird abundance and richness and an increase in evenness between the most and least humid season at each of the three elevations. Climatic factors were more closely related to these temporal fluctuations than local resource availability. While temperature had significant positive effects on the abundance of birds at mid and high elevations, precipitation negatively affected bird abundance at low and mid elevations. Our study highlights that bird assemblages along tropical elevational gradients can show pronounced seasonal fluctuations. In particular, low temperatures and high precipitation seem to impose important constraints on birds. We conclude that potential changes in climate, due to global warming, are likely to affect the spatio-temporal dynamics of bird assemblages along tropical elevational gradients.

The distribution and ecology of the assemblages of myxomycetes associated with four different microhabitats were studied in Big Bend National Park in Texas. During Mar. 2005, twelve plots (30 × 30 m) were established along an elevational gradient that extended from 564 to 1807 m. Samples of aerial bark from dead and living trees, aerial litter (dead but still attached plant parts), ground litter (fallen dead plant parts) and ground bark (fragments of fallen bark) were collected from these plots, which encompassed all of the major vegetation types found in the Park. Four hundred forty-seven moist chambers were prepared, and 95.8 % (428) produced some evidence (either fruit bodies or plasmodia) of myxomycetes. A total of 71 species were recorded, with ground litter yielding most (45 species). Aerial litter, aerial bark and ground bark yielded 44, 39 and 37 species, respectively. Species abundance distribution measures (diversity, dominance and similarities) varied among the four microhabitats as well as among the major vegetation types. Canonical Correspondence Analysis (CCA) showed that species distribution patterns were closely related to: (1) the major environmental-complex gradients associated with differences in elevation/temperature/moisture conditions that occur from one locality to another; and (2) the different types of microhabitat.

Determinate growth involves cessation of leaf formation prior to the end of the growing season, whereas indeterminate growth involves leaf formation for as long as environmental conditions allow. Quaking aspen ( Populus tremuloides Michx.) has been described as having both types of growth. This variation is partially due to canopy bud position, but environmental factors may also contribute. In this study, buds from the same canopy position of aspen trees in northern Colorado, USA, exhibited less neoformation with increasing elevation (R2= 0.78). Evidence suggests that this is primarily a response to the characteristically cooler temperatures and shorter growing seasons of higher elevations.

In order to better understand the influence of short elevational gradient on the attributes of bryophyte communities, we examined the bryophyte flora within six elevational belts (10, 50, 400, 800, 950, and 1170 m a.s.l.) on a mountain in the Atlantic Forest in southeastern Brazil. Ten subplots (10 × 10 m) distributed randomly in 1 ha forest plot of forest at each elevation were surveyed. A total of 253 species were encountered and the richness did not vary depending significantly on elevation. The floristic similarities of the elevational belts were high > 50%, with the exception of the Mountaintop forest (< 35%), and the classification analyses indicated groups defined by Atlantic Forest vegetation types. Endemism demonstrated a positive correlation with elevation, while the amplitudes of the phytogeographical patterns of the species diminished with increasing elevation. The dioicous condition predominated in all of the elevational belts, and the dioicous/monoicous ratio showed an inverted-parabolic pattern along the gradient. Data concerning bryophyte species richness and distributions will be useful in future projects monitoring the effects of climate change on tropical forests.

We evaluated species‐environment relationships within pinon‐juniper woodlands in northern New Mexico (United States) using canonical correspondence analysis (CCA). The first CCA axis was associated primarily with elevation. Our results showed separation between pinon and juniper along the elevation gradient, as expected: pinon is relatively more dominant at higher sites, whereas juniper is relatively more dominant at lower sites. To examine how this pattern of dominance might emerge with time, we plotted the position of centroids for three pinon and juniper size classes along the first CCA axis. We found that small pinons and junipers were distributed relatively uniformly across the gradient, whereas large pinons and junipers were strongly segregated along the gradient, with intermediate‐sized pinons and junipers intermediate on the CCA axis between small and large. This produced a pattern of increased divergence between the two species that increased with size. We suggest that this pattern emerges as a r...