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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.

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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.

Made available in DSpace on 2022-04-28T19:48:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Despite the important role of the order Odonata in ecosystems, there is a lack of information about dragonfly communities in several regions, high elevation sites, and environmentally protected areas in Minas Gerais State, Brazil. Our objective was to assess the abundance and richness of dragonfly and damselfly communities along an elevational gradient in the Atlantic Forest, southeastern Brazil. This study was conducted in the Fernão Dias Environmental Protection Area, Mantiqueira Mountain region, Gonçalves, Minas Gerais State, in sites covered by Seasonal Semi-deciduous and mixed forests. This is the first study of Odonata communities in the region. Sam-plings were carried out on 17 days from October 2019 to March 2020 at three elevation ranges (low, mid, and high). A total of 293 specimens, distributed in 39 species and 9 families, were sampled. Elevation did not influence the richness or abundance of dragonflies but altered community com-position. Some species were found to be exclusive to high-elevation sites, such as Heteragrion mantiqueirae Machado, 2006, which was recorded for the first time in Minas Gerais and we pro-vide a description and diagnosis of the single female collected in tandem. A novel species of the genus Brechmorhoga was found to occur at mid and high elevations. The composition of dragonfly communities depends on the degree of preservation and extension of forest areas. Therefore, conservation of forests in Gonçalves is crucial for preserving Odonata diversity in Minas Gerais State. Instituto Federal de Educação Ciência e Tecnologia do sul de Minas Gerais Inconfidentes Departamento de Biodiversidade Evolução e Meio Ambiente Programa de Pós-Graduação em Ecolo-gia de Biomas Tropicais Universidade Federal de Ouro Preto Departamento de Zoologia Universidade Estadual Paulista Departamento de Genética Ecologia e Evolução Programa de Pós-Graduação em Ecologia Conserva-ção e Manejo da Vida Silvestre Universidade Federal de Minas Gerais Instituto Federal de Educação Ciência e Tecnologia do Paraná Department of Biology University of São Paulo (USP) Departamento de Zoologia Universidade Estadual Paulista

Recent work on tropical montane small mammals and birds has shown that abundance–elevational range size relationships (i.e., the relationship between abundance of a species and its elevational range size) can be manifested in a number of distinct generalized patterns. To understand why different patterns occur, one first must understand the causal mechanisms behind patterns of interspecific variation in species abundance and elevational range size. Using small mammal data along five elevational gradients in Southwest China, we assessed the relative importance of body mass, niche position (i.e., how typical the environmental conditions in which a species occurs are of the full set of conditions under consideration) and niche breadth in explaining the interspecific variation in mean abundance of species of small mammals, and elevational range size. Niche position and niche breadth were calculated using outlying mean index analysis based on 24 environmental variables. The relative importance of body mass, niche position, and niche breadth, in explaining the mean abundance and elevational range size of species were examined using phylogenetic regression and phylogenetic path analyses. Along each of five elevational gradients, body mass maintained a nonsignificant (P > 0.05) relationship both with mean abundance and elevational range size when the effects of phylogeny were taken into account. Niche position had a negative effect on mean abundance and elevational range size (species with a niche position close to edge environmental conditions were rarer and had smaller elevational range sizes) across five gradients (significant negative effect: three gradients for mean abundance; five gradients for elevational range size). Conversely, a positive effect of niche breadth on mean abundance and elevational range size was observed consistently, yet the effect was significant only for some gradients (mean abundance: two gradients; elevational range size: four gradients). Our study suggests that niche position and niche breadth both are good predictors of abundance and elevational range size of montane small mammals; niche position and niche breadth therefore play a strong role in the formation of abundance–elevational range size relationship.

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.

International audience; Ant communities are extremely diverse and provide a wide variety of ecological functions in tropical forests. Here we investigated the abiotic factors driving ant composition turnover across an elevational gradient at Mont Itoupé, French Guiana. Mont Itoupé is an isolated mountain whose top is covered by cloud forests, a biogeographical rarity that is likely to be threatened according to climate change scenarios in the region. We examined the influence of six soil, climatic and LiDAR derived vegetation structure variables on leaf-litter ant assembly (267 species) across nine 0.12-ha plots disposed at three elevations (ca. 400, 600 and 800m asl). We tested (a) whether species cooccurring within a same plot or a same elevation were more similar in terms of taxonomic, functional and phylogenetic composition, than species from different plots/elevations, and (b) which environmental variables significantly explained compositional turnover among plots. We found that the distribution of species and traits of ant communities along the elevational gradient was significantly explained by a turnover of environmental conditions, particularly in soil phosphorus and sand content, canopy height and mean annual relative humidity of soil. Our results shed light on the role exerted by environmental filtering in shaping ant community assembly in tropical forests. Identifying the environmental determinants of ant species distribution along tropical elevational gradients could help predicting the future impacts of global warming on biodiversity organization in vulnerable environments such as cloud forests.

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.

Environmental variation along an elevational gradient can yield phenotypic differentiation resulting from varying selection pressures on plant traits related to seasonal responses. Thus, genetic clines can evolve in a suite of traits, including the circadian clock, that drives daily cycling in varied traits and that shares its genetic background with adaptation to seasonality. We used populations of annual Mimulus laciniatus from different elevations in the Sierra Nevada in California to explore among-population differentiation in the circadian clock, flowering responses to photoperiod, and phenological traits (days to cotyledon emergence, days to flowering, and days to seed ripening) in controlled common-garden conditions. Further, we examined correlations of these traits with environmental variables related to temperature and precipitation. We observed that the circadian period in leaf movement was differentiated among populations sampled within about 100 km, with population means varying by 1.6 h. Significant local genetic variation occurred within 2 populations in which circadian period among families varied by up to 1.8 h. Replicated treatments with variable ecologically relevant photoperiods revealed marked population differentiation in critical day length for flowering that ranged from 11.0 to 14.1 h, corresponding to the time period between late February and mid-May in the wild. Flowering time varied among populations in a 14-h photoperiod. Regardless of this substantial population-level diversity, obvious linear clinality in trait variability across elevations could not be determined based on our genotypic sample; it is possible that more complex spatial patterns of variation arise in complex terrains such as those in the Sierra Nevada. Moreover, we did not find statistically significant bivariate correlations between population means of different traits. Our research contributes to the understanding of genetic variation in the circadian clock and in seasonal responses in natural populations, highlighting the need for more comprehensive investigations on the association between the clock and other adaptive traits in plants.

We evaluated the spatial characteristics of the first day of peak leaf colouring (PLCstart) and their relationships with air temperature along latitudinal and elevational gradients in Japan from 2015 to 2017. Leaf colouring information collected from more than 740 sites via citizen science was analysed, representing elevations from 0 to 2800 m and latitudes from 32°N to 44°N. We found that locations with earlier PLCstart dates (day of year 265–294) displayed steeper slopes in elevation per degree of latitude than locations with later PLCstart dates (day of year 295–314). This statistically significant result indicates that the influence of elevation on PLCstart (vertical gradient) weakened as the leaf colouring season progressed in Japan. In addition to these spatial characteristics, the PLCstart and the warmth index (based on monthly mean air temperature) showed significant linear correlations for latitudinal and elevational gradients. This result suggests that the sensitivity of PLCstart to air temperature, as manifested in both latitudinal and elevational gradients, is constant. This study suggests that online phenological data may provide more accurate results for a regional scale (100–1000 km) than the datasets used by previous studies.

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.

Phosphorus (P) bioavailability is an important factor in alpine meadows and plays an important role in the response to climate change and the maintenance of ecosystem functioning. However, little is known about how environmental factors, such as elevation and slope aspect, affect soil P bioavailability. We explored the effects of elevational gradient and slope aspect on different forms of P and P availability in the alpine meadows on the southern slope of the Tian Shan Mountain range. Total P was found to be 851.9–1556.7 mg·kg−1 at different elevational gradients and 437.5–1547.0 mg·kg−1 at different slope aspects, and highest at 3337 and 3652 m.a.s.l., but little differences between slope aspects. Olsen P and Labile P linearly increased with the elevational gradient. The valley and the base of the shady slope had higher contents of H2O-Po, NaHCO3-Pi, and NaHCO3-Po, and high-active organic P (NaHCO3-Po, NaOH-Po, and H2O-Po) was positively correlated with soil total carbon (TC), total nitrogen (TN), soil organic carbon (SOC), and aboveground biomass (AGB), but was negatively correlated with pH, aluminum (Al), and calcium (Ca) at different elevational gradients. High-active bioavailable P (H2O-Pi, H2O-Po, NaHCO3-Pi, and NaHCO3-Po) was positively correlated with soil SOC and AGB and was negatively correlated with pH at different slope aspects. Our results suggest that soil P availability in alpine meadows is significantly controlled by topographical factors and the valleys and base of shady slopes are reservoirs of high-active bioavailable P.

The dependence of air temperature on elevation (i.e., its elevational gradient) in the mountains is well known. However, the elevational gradient of near-surface ground temperatures and derived thermal parameters is much less understood. In this study, we investigated how these parameters depend on elevation by one-year temperature measurements along a transect in the Valais Alps (Switzerland) between 700 and 2,600 m a.s.l. In addition, we studied the effect of differences in slope aspect (north/south) and land cover (open field/forest). Air temperatures were measured as a reference. The results show that the ground thermal regime distinctly differs from that of the air. These differences could mainly be attributed to radiation, snow cover, and ground heat transfer. Our findings have far-reaching implications for ecosystems, agriculture, and forestry in mountains because a large portion of the living biomass is underground and thus affected by ground thermal processes.

Despite the long-standing interest in the organization of ant communities across elevational gradients, few studies have incorporated the evolutionary information to understand the historical processes that underlay such patterns. Through the evaluation of phylogenetic α and β-diversity, we analyzed the structure of leaf-litter ant communities along the Cofre de Perote mountain in Mexico and inferred its putative driving forces. Lowland and some highland sites showed phylogenetic clustering, whereas intermediate elevations and the highest site presented phylogenetic overdispersion. We infer that strong environmental constrains found at the bottom and the top elevations are favoring closely-related species to prevail at those elevations. Conversely, more benign conditions at intermediate elevations suggest interspecific interactions being more important in these environments. Total phylogenetic dissimilarity was driven by the turnover component, indicating that the turnover of ant species along the mountain is actually shifts of lineages adapted to particular locations resembling their ancestral niche. The greater phylogenetic dissimilarity between communities was related to greater temperature distances probably due to narrow thermal tolerances inherit to several ant lineages that evolved in more stable conditions. Our results suggest that the interplay between environmental filtering, interspecific competition and habitat specialization plays an important role in the assembly of leaf-litter ant communities along elevational gradients.

Beta diversity represents how species in the regional pool segregate among local communities and hence forms a link between local and regional species diversities. Therefore, the magnitude of beta diversity and its variation across geographic gradients can provide insights into mechanisms of community assembly. Along with limits on local or regional level diversities, effects of local abundance that lead to under-sampling of the regional species pool are important determinants of estimated beta diversity. We explore the effects of regional species pools, abundance distributions, and local abundance to show that patterns in beta diversity as well as the mean of species abundance distribution have distinct outcomes, depending on limits on species pools and under-sampling. We highlight the effect of under-sampling in some established relationships between gamma diversity and beta diversity using graphical methods. We then use empirical data on ant communities across an elevational gradient in the Eastern Himalayas to demonstrate a shift from effect of reduction in species pool to under-sampling at mid-elevations. Our results show that multiple processes with contrasting effects simultaneously affect patterns in beta diversity across geographic gradients.

Andean forests are home to a strikingly high diversity of plants, making it difficult to understand the main drivers of species assembly. Trait-based approaches, however, help overcome some challenges associated with high taxonomic complexity, providing insights into the main drivers of species coexistence. Here, we evaluated the roles of climate, soil fertility, and symbiotic root associations on shaping the assembly of six plant functional traits (leaf area, specific leaf area, dry leaf matter content, leaf thickness, leaf toughness, and wood density) along an elevational gradient in the species-rich northwestern Andean forests of Colombia. The two main axes of the correspondence RLQ analysis explained 95.75% of the variability. The first axis was associated with the leaf economic spectrum, while the second axis with the tradeoff between growth and survival. Furthermore, the fourth corner method showed that both regional (climatic variables) and local factors (soil fertility, symbiotic root associations, and light distribution) played a key role in determining plant trait assembly. In summary, our study emphasizes the importance of considering both individual size and local factors to better understand drivers of plant trait assembly along environmental gradients.

Simple Summary Certain moths defend themselves with toxic substances, and they show this to predators with bright and contrasting coloration. At high elevations, fewer birds, bats and other predators are present that feed on these insects. We therefore expected a decreasing proportion of colorful tiger and lichen moths with increasing elevation. Our study was carried out in forests between 1040 and 2670 m in the Ecuadorian Andes. We scored all 353 observed species according to their warning coloration, and whether they mimic bees and wasps or potentially poisonous beetles. We also measured forewing length of all species. From these data community-weighted means were calculated and related to the elevation of their collection sites. As predicted, the communitywide incidence of all three defensive traits decreased substantially from tall premontane forest to open upper montane forest. In parallel, moth size increased with elevation. Moreover, the systematic composition of tiger and lichen moth assemblages changed substantially. These findings support the idea that different selection regimes favor warning coloration at lower sites with higher predation pressure, while cryptic appearance is more advantageous at higher elevations. Abstract On tropical mountains, predation pressure decreases with elevation. Accordingly, one expects an elevational decay in the prevalence of costly defensive traits such as aposematic coloration. Using light-trap catches of Arctiinae moths (353 species, 4466 individuals), assembled along a forested gradient in the megadiverse tropical Andes of southern Ecuador, we show that the incidence of aposematic coloration decreases strongly between 1040 and 2670 m asl. While over 60% of Arctiinae moths were warningly colored at lowest sites, this fraction decreased to less than 20% in montane forest, yet increased slightly again at the highest sites in the very open Purdiaea nutans forest. In parallel, the incidence of hymenopteran mimics and of species that mimic chemically defended beetles decreased with elevation. Hymenopteran mimics accounted for less than 5% of Arctiinae moths at sites above 2100 m, and beetle mimics were essentially lacking at high elevations. These patterns coincide with a change in gross taxonomic composition of Arctiinae ensembles and with an increase in average body size towards higher elevations. Representatives of Euchromiina and Ctenuchina became scarce with altitude, whereas the prevalence of Lithosiinae increased. Our findings suggest that the variable selective pressures along the elevational gradient favor warning coloration primarily at lower sites, whereas cryptic appearance of adult moths dominates in the tropical upper montane forest.