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opencc-zeroDec 2018View details →

Data from: Differences in carbon stocks along an elevational gradient in tropical mountain forests of Colombia

Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variation of carbon stocks along elevational gradients that correspond to well-defined temperature gradients. We predicted that carbon stored in live aboveground biomass, aboveground necromass, and soil components of forests on the eastern flank of the Colombian Andes would change with elevation along this gradient extending from 750 to 2800 m above sea level. The rationale was that the corresponding change in temperature (14°C to 26°C) would influence tree growth and decomposition of organic matter. To address this hypothesis, we examined the carbon stored in these three components using data from 20 0.25-ha plots located along this elevational gradient. The mean total carbon stock found in the study region was 241.3±37.5 Mg C/ha. Aboveground carbon stocks decreased with elevation (p =0.001), as did necromass carbon stocks (p =0.016). Although soil organic carbon stocks did not differ significantly along the gradient (p =0.153), they contributed proportionately more at higher than at lower elevations, counterbalancing the opposite trends in aboveground carbon and necromass carbon stocks. As such, total carbon stocks did not vary significantly along the elevational gradient (p =0.576).

Data from: Soil microbial biomass increases along elevational gradients in the tropics and sub-tropics but not elsewhere

Abstract Aim: Our aim is to use elevational gradients to quantify the relationship between temperature and ecosystem functioning. Ecosystem functions such as decomposition, nutrient cycling and carbon storage are linked with the amount of microbial biomass in the soil. Previous studies have shown variable relationships between elevation and soil microbial biomass (SMB). Understanding the biological mechanisms linking SMB with elevational gradients will shed light on the environmental impacts of global warming. Location: Global. Time period: 2002-2018. Major taxa studied: Soil microbes. Method: We performed a global meta-analysis of the relationships between SMB and elevation. Data were collected from 59 studies of 73 elevational transects from around the world. Results: We found no consistent global relationship between SMB and elevation. SMB increased significantly with elevation in the tropics and sub-tropics, but not in other climate zones. However, we found consistent positive relationships between SMB, soil organic carbon and total nitrogen concentrations. Main conclusions: Our results suggest that global warming will impact tropical and sub-tropical ecosystems more severely than colder regions. Tropical ecosystems, already at risk from species extinctions, will likely experience declines in SMB as the climate warms, resulting in losses of fundamental ecosystem functions such as nutrient cycling and carbon storage.

opencc-zeroAug 2020View details →

Do dense layers of invasive plants elevate the foraging intensity of small mammals in temperate deciduous forests? A case study from Pennsylvania, USA

Monospecific stands of invasive plants can dramatically restructure habitat for fauna, thereby elevating population densities or promoting foraging of consumer species who benefit in the altered habitat. For example, dense stands of invasive plants may protect small mammals from predators, which in turn could increase foraging pressure on seeds that small mammals feed upon. We used a before-after, control-impact experimental design to test whether small mammal capture rates were higher and giving-up densities (GUDs) lower beneath dense stands of Berberis thunbergii, an invasive shrub with a rapidly expanding range throughout eastern North America. Our experimental design included three plot categories: 1) plots heavily invaded by B. thunbergii, 2) control plots lacking invasive shrub cover, and 3) invaded plots where we eradicated B. thunbergii midway through the study. Although our overall small mammal capture rate was low, small mammal captures were 65% higher in B. thunbergii invaded habitat relative to control plots and eradication lowered capture rates by 77%. GUDs were also 26% higher within B. thunbergii relative to control plots and eradication decreased GUDs by 65%. Our findings suggest that small mammals perceive dense stands of B. thunbergii as relatively safe foraging habitat. Prior surveys within our study locations revealed dramatically depressed tree seedling densities under B. thunbergii, thus invasive plants may promote intensive foraging by small mammals and reduce recruitment for species with foraged seeds or seedlings.

opencc-zeroAug 2020View details →

Data from: Lower elevation animal species do not tend to be better competitors than their upper elevation relatives

Abstract Aim: What factors set species' range edges? One general hypothesis, often attributed to Darwin and MacArthur, is that interspecific competition prevents species from inhabiting the warmest portions along geographic gradients (i.e., low latitudes or low elevations). A prediction arising from this Darwin-MacArthur hypothesis is that lower elevation species are better competitors than related upper elevation species. An alternative prediction is that upper elevation taxa will tend to be better competitors because they will tend to be larger (Bergmann's rule). Here, I test these opposing predictions. Location: Global. Time period: 1971 – 2019. Major taxa studied: Birds, mammals, amphibians, fishes. Methods: I conducted a meta-analysis of studies that have measured pairwise behavioral aggression between species-pairs of closely related animals where the two species inhabit divergent elevational distributions. Results: I found that (1) interspecific aggression appears to be a reliable indicator of interspecific competition; (2) elevational position was not consistently linked to interspecific aggression—while lower elevation songbird species in the tropics showed stronger interspecific aggression in response to playback experiments, upper elevation species showed stronger interspecific aggression in direct observations of interspecific aggression across a range of taxa and latitudes; (3) body size was a good predictor of pairwise interspecific aggression and (4) there was limited evidence for Bergmann's rule. Main conclusions: My results do not support the longstanding prediction that lower elevation animals are generally better competitors than their upper elevation relatives. Instead, patterns of interspecific aggression are linked to body size, with larger animals showing more aggression towards smaller relatives than vice versa. Hence, a trait—body size—that is idiosyncratically related to elevational position appear to determine the outcome of pairwise behavioral interactions. Last, I consider these results in the context of the hypothesis that behavioral interactions may impact rates of upslope range shifts associated with recent warming.

opencc-zeroAug 2020View details →

Data from: Joint effect of phylogenetic relatedness and trait selection on the elevational distribution of Rhododendron species

Congeneric species may coexist at fine spatial scales through niche differentiation, however, the magnitude to which the effects of functional traits and phylogenetic relatedness contribute to their distribution along elevational gradients remains understudied. To test the hypothesis that trait and elevational range overlap can affect local speciesʼ coexistence, we first compared phylogenetic relatedness and trait (including morphological traits and leaf elements) divergence among closely related species of Rhododendron L. on Yulong Mountain, China. We then assessed relationships between the overlap of multiple functional traits and the degree of elevational range overlap among species pairs in a phylogenetic context. We found that phylogeny was a good predictor for most functional traits, where closely related species showed higher trait similarity and occupied different elevational niches at our study site. Species pairs of R. subgen. Hymenanthes (Blume) K. Koch showed low elevational range overlap and some species pairs of R. subgen. Rhododendron showed obvious niche differentiation. Trait divergence is greater for species in R. subgen. Rhododendron, and it plays an important role between species pairs with low elevational range overlap. Trait convergent selection takes place between co-occurring closely related species that have high elevational range overlap, which share more functional trait space due to environmental filtering or ecological adaptation in more extreme habitats. Our results highlight the importance of evolutionary history and trait selection for species coexistence at fine ecological scales along environmental gradients.

Data from: Plants are more likely to be spiny at mid-elevations in the Qinghai-Tibetan Plateau, south-western China

Aim: We tested the elevational herbivory defence hypothesis, which predicts that plants from low elevations are better defended than plants from higher elevations. Location: The Qinghai-Tibetan Plateau in south-western China - the world's highest plateau. Major taxa studied: Angiosperms. Methods: We collated binary spinescence data for 10,622 angiosperm species ranging from 600 to 6,000 m a.s.l. Logistic regression was used to quantify the elevational pattern in spinescence. Because spinescence is thought to be especially effective against mammalian herbivores, we also quantified the association between spinescence and mammalian herbivore richness. Results: We found a unimodal relationship between elevation and spinescence, with the highest proportion of spinescent species occurring at mid-elevations. This unimodal relationship was present in perennial herbs, shrubs and trees, but not in annual herbs. Herbivorous mammal richness also showed a unimodal elevational pattern. A positive association between herbivorous mammal richness and the incidence of spinescent species suggests that elevational variation in herbivore pressure from mammals might drive elevational variation in spinescence. Main conclusions: Our findings further call into question the elevational herbivory defence hypothesis and shed new light on the potential causes of elevational gradients in plant diversity.

Data from: Cyanophage propagation in the freshwater cyanobacterium Phormidium is constrained by phosphorus limitation and enhanced by elevated pCO2

Intensification of human activities has led to changes in the availabilities of CO2 and nutrients in freshwater ecosystems, which may greatly alter the physiological status of phytoplankton. Viruses require hosts for their reproduction and shifts in phytoplankton host physiology through global environmental change may thus affect viral infections as well. Various studies have investigated the impacts of single environmental factors on phytoplankton virus propagation, yet little is known about the impacts of multiple factors, particularly in freshwater systems. We therefore tested the combined effects of phosphorus limitation and elevated pCO2 on the propagation of a cyanophage infecting a freshwater cyanobacterium. To this end, we cultured Phormidium in P-limited chemostats under ambient (400 µatm) and elevated (800 µatm) pCO2 at growth rates of 0.6, 0.3, and 0.05 d-1. Host C:P ratios generally increased with strengthened P-limitation and with elevated pCO2. Upon host steady state conditions, virus growth characteristics were obtained in separate infection assays where hosts were infected by the double-stranded DNA cyanophage PP. Severe P-limitation (host growth 0.05 d-1) led to a 85% decrease in cyanophage production rate and a 73% decrease in burst size compared to the 0.6 d-1 grown P-limited cultures. Elevated pCO2 induced a 96% increase in cyanophage production rate and a 57% increase in burst size, as well as an 85% shorter latent period as compared to ambient pCO2 at the different host growth rates. In addition, elevated pCO2 caused a decrease in the plaquing efficiency and an increase in the abortion percentage for the 0.05 d-1 P-limited treatment, while the plaquing efficiency increased for the 0.6 d-1 P-limited cultures. Together, our results demonstrate interactive effects of elevated pCO2 and P-limitation on cyanophage propagation, and show that viral propagation is generally constrained by P-limitation but enhanced with elevated pCO2. Our findings indicate that global change will likely have a severe impact on virus growth characteristics and thereby on the control of cyanobacterial hosts in freshwater ecosystems.

opencc-by-4.0Feb 2020View details →

zenodo32/100

ICECAP-2 consortium bed elevation model for Princess Elizabeth Land, East Antarctica

We present a new topographic digital elevation model (DEM) for Princess Elizabeth Land (PEL) – the last remaining region in Antarctica to be surveyed. The DEM covers an area of 899,730 km2 and was established from new aero geophysical data collected by the ICECAP-2 consortium, led by the Polar Research Institute of China, from four different surveys since 2015. Two products are available; (1) 500 m bed elevation model; and (2) 500 m ice thickness model. The mass conservation (MC) method is used to infer ice thickness DEM across faster-flowing (>30 m yr-1) regions of the ice sheet, and streamline diffusion at slower-flowing areas. The ice thickness DEM is then integrated with the ice surface DEM from the Reference Elevation Model of Antarctica (Howat, et al., 2019) to generate the bed elevation model. Together with BedMachine Antarctica, and Bedmap2, this new bed DEM for PEL completes the first-order measurement of subglacial Antarctica – an international mission that began 70 years ago.

Data from: Experimental migration upward in elevation is associated with strong selection on life history traits

One of the strongest biological impacts of climate change has been the movement of species poleward and upward in elevation. Yet, what is not clear, is the extent to which the spatial distribution of locally adapted lineages and ecologically important traits may also shift with continued climate change. Here, we take advantage of a transplant experiment mimicking up-slope seed dispersal for a suite of ecologically-diverse populations of yellow monkeyflower (Mimulus guttatus sensu lato) into a high-elevation common garden during an extreme drought period in the Sierra Nevada mountains, California, USA. We use a demographic approach to quantify fitness and test for selection on life history traits in local vs. lower-elevation populations and in normal vs. drought years to test the potential for up-slope migration and phenotypic selection to alter the distribution of key life history traits in montane environments. We find that lower-elevation populations tend to outperform local populations, confirming the potential for up-slope migration. Although selection generally favored some local montane traits, including larger flowers and larger stem size at flowering, drought conditions tended to select for earlier flowering typical of lower elevation genotypes. Taken together, this suggests that monkeyflower lineages moving upward in elevation could experience selection for novel trait combinations, particularly under warmer and drier conditions that are predicted to occur with continued climate change.

Environmental DNA (eDNA) from multiple pathogens is elevated near active Atlantic salmon farms

The spread of infection from reservoir host populations is a key mechanism for disease emergence and extinction risk and is a management concern for salmon aquaculture and fisheries. Using a quantitative environmental DNA methodology, we assessed pathogen eDNA in relation to salmon farms in coastal British Columbia, Canada, by testing for 39 species of salmon pathogens (viral, bacterial, and eukaryotic) in 134 marine environmental samples at 58 salmon farm sites (both active and inactive) over three years. Environmental DNA from twenty-two pathogen species was detected 496 times and species varied in their occurrence among years and sites, likely reflecting variation in environmental factors, other native host species, and strength of association with domesticated Atlantic salmon. Overall, we found that the probability of detecting pathogen eDNA was 2.72 (95% CI: 1.48, 5.02) times higher at active versus inactive salmon farm sites and 1.76 (95% CI: 1.28, 2.42) times higher per standard deviation increase in domesticated Atlantic salmon eDNA concentration at a site. If the distribution of pathogen eDNA accurately reflects the distribution of viable pathogens, our findings suggest that salmon farms serve as a potential reservoir for a number of infectious agents; thereby elevating the risk of exposure for wild salmon and other fish species that share the marine environment.

Data from: Collective aggressiveness limits colony persistence in high but not low elevation sites in Amazonian social spiders

Identifying the traits that foster group survival in contrasting environments is important for understanding local adaptation in social systems. Here we evaluate the relationship between the aggressiveness of social spider colonies and their persistence along an elevation gradient using the Amazonian spider, Anelosimus eximius. We found that colonies of A. eximius exhibit repeatable differences in their collective aggressiveness (latency to attack prey stimuli), and that colony aggressiveness is linked with persistence in a site-specific manner. Less aggressive colonies are better able to persist at high-elevation sites, which lack colony-sustaining large-bodied prey, whereas colony aggression was not related to chance of persistence at low-elevation sites. This suggests that low aggressiveness promotes colony survival in high-elevation, prey-poor habitats, perhaps via increased tolerance to resource limitation. These data reveal that the collective phenotypes that relate to colony persistence vary by site, and thus, the path of social evolution in these environments is likely to be affected.

Data from: Using functional and phylogenetic diversity to infer avian community assembly along elevational gradients

Aim We present the first global analysis of elevational gradients in functional and phylogenetic diversity of birds and test for signals of deterministic processes (i.e., environmental filtering and limiting similarity) in community assembly. Further, we examine for latitudinal effects in the strength of these processes. Location Forty-six elevational gradients across the globe. Time period Current (between 1924 and 2016) Major taxa Birds. Methods We systematically selected, compiled and analyzed published data on bird diversity along elevational gradients. For each gradient, we calculated functional and phylogenetic diversity across elevations and described the main patterns for each diversity metric. Then, we calculated standardized effect sizes (SES) of each metric and used these SES values to (1) test the signals of deterministic processes shaping assemblages across elevations and (2) to compare changes in within-mountain diversity, among mountains located at different latitudes. Results Birds displayed eight different patterns of functional and phylogenetic diversity across elevations, but no global pattern of increase or decrease was found. There is, however, a consistent global pattern of phylogenetic clustering, with mountain species being more closely related to each other at any given elevation. Latitude had a significant effect on within-mountain changes in functional and phylogenetic diversity across elevations, with more negative slopes (stronger decline in diversity metrics with increasing elevation) in tropical mountains. Main conclusions Our findings challenge the idea that the decline of functional and phylogenetic diversity with elevation is a general pattern, emphasizing the uniqueness of each mountain system. In spite of this great variability, we found a latitudinal effect in the patterns of within-mountain functional and phylogenetic dispersion of birds after controlling for effects of species richness. Environmental filtering, thus, may act differently in tropical and temperate mountains, and calls for more comparative studies on the mechanisms driving community assembly at different latitudes.

Adaptation to elevation but limited local adaptation in an amphibian

We performed a reciprocal transplant experiment to estimate "parallel" adaptation to elevation and "unique" adaptation to local sites at the same elevation, using the frog Rana temporaria in the Swiss Alps. It is important to distinguish these two processes because they have different implications for population structure and ecological specialization. Larvae were reared from hatching to metamorphosis within enclosures installed in their pond of origin, in three foreign ponds at the same elevation, and in four ponds at different elevation (1500-2000 m higher or lower). There were two source populations from each elevation, and adults were held in a common environment for one year before they were crossed to produce offspring for the experiment. Fitness was a measure that integrated larval survival, development rate, and body size. Parallel adaptation to elevation was indicated by an advantage at the home elevation (11.5% fitness difference at low elevation and 47% at high elevation). This effect was stronger than that observed in most other studies, according to a survey of previous transplant experiments across elevation (N = 8 animal species and 71 plants). Unique local adaptation within elevational zones was only 0.3-0.7 times as strong as parallel adaptation, probably because gene flow is comparatively high among nearby wetlands at the same elevation. The home-elevation advantage may reduce gene flow across the elevational gradient and enable the evolution of habitat races specialized on elevation.

Spider diversity across an elevation gradient in Área de Conservación Guanacaste (ACG), Costa Rica

Throughout the Neotropics, temperature and precipitation change with elevation and these changes affect the assemblage of species at any particular elevation. We documented the diversity of litter-inhabiting spiders, (Arachnida: Araneae) along a Costa Rican elevational gradient as it relates to covarying abiotic factors such as temperature and precipitation. The spiders we collected were principally unidentifiable juveniles and so we used Barcode Index Numbers (BINs) derived from DNA barcodes as proxies for species-level interim names. We contrasted these taxon-based estimates with phylogenetic measures of alpha and beta diversity derived from both the mitochondrial DNA barcode region and a multi-gene phylogeny of spiders and found that neither the abundance nor the species-richness of spiders was significantly correlated with elevation, temperature or precipitation. However, we did find that spider assemblages in the upper elevation cloud forests were phylogenetically clustered, (and this pattern was unrelated to whether the phylogenetic patterns were derived mitochondrially or from a multi-gene analysis). One standard explanation for such a pattern is that harsh abiotic conditions in higher elevation forests have selected for particular spider lineages however this remains to be tested fully. The diversity of leaf-litter spider species we uncovered was high and further sampling of spider abundance and diversity across the ACG is likely to yield many new species.

Elevation and landscape change drive the distribution of a montane, endemic grassland bird

This dataset documents the presence and abundance of the Nilgiri pipit (Anthus nilghiriensis) in 170 survey sites across most of its global range. Between one and four surveys were carried out at each site between November 2017 and May 2018 by experienced observers. Survey duration was proportional to site area. A wide range of habitat characteristics were also surveyed, and additional habitat characteristics for each site were gathered from remotely sensed data.

opencc-by-4.0Oct 2020View details →

zenodo32/100

Allometric trajectories in Picea abies [L.] Karst. trees remain stable despite differences in temperature, phenology and growth along an elevational gradient.

Dataset for the manuscript "Allometric trajectories in Picea abies [L.] Karst. trees remain stable despite differences in temperature, phenology and growth along an elevational gradient.".

Data on epiphytic lichens along elevational gradients in South Tyrol, Italy

1. Several studies have evaluated lichen responses in terms of shifts in species climate suitability, species richness, and community composition. In contrast, patterns of co-occurrence among species that could be related to complex species interactions have received less consideration. Biotic interactions play a major role in shaping species niches, fitness, and adaptation to new environments. Therefore, considering the specific relationships among co-occurring species is essential to further deepen our knowledge of biodiversity response to climate change. In this perspective, the analysis of lichen ecological networks across elevational gradients may provide a powerful tool to understand how communities are structured and how biotic interactions are modulated by changing climatic conditions. 2. We evaluated the contribution of environmental and species biological attributes to the structure of epiphytic lichen-host tree networks. Specifically, we studied lichen communities considering two different network levels: the whole lichen community, and groups of lichen species that presented similar biological traits. In this framework, we (1) characterized the structure of the epiphytic lichen-host tree networks; (2) assessed how network structure varied with climate, forest attributes, and community trait diversity; and (3) evaluated the role that biological traits played in the connections established between co-occurring lichens. 3. On one hand, results indicate that epiphytic lichen communities are dominated by local segregation, suggesting habitat specialization among lichens within their host tree, and that climatic conditions and, to a lesser extent, lichen diversity are the main drivers of community assemblage. On the other hand, the role of lichen species in the networks depends on their particular biological traits, supporting the hypothesis that biological traits contribute to shape network structure by influencing the ability of the species to interact between each other. These findings warn about the potential impact of climate change on epiphytic lichen communities. 4. Synthesis. This study builds towards a better understanding of lichen community assembly and on biodiversity response to climate change in forest alpine ecosystems. In particular, our results highlight the value of lichen-tree networks to inform about assemblage processes acting at different organizational levels and indicate that lichens might become one of the most threatened groups under global change scenarios.

Large losses of ammonium-nitrogen from a rice ecosystem under elevated CO2

Inputs of nitrogen into terrestrial ecosystems, mainly via the use of ammonium-based fertilizers in agroecosystems, are enormous, but its fate under elevated atmospheric carbon dioxide (CO2) is not well understood. We have taken advantage of a 15-year free air CO2 enrichment study to investigate the influence of elevated CO2 on the transformation of ammonium-nitrogen in a rice ecosystem in which ammonium is usually assumed to be stable under anaerobic conditions. We demonstrate that elevated CO2 causes substantial losses of ammonium-nitrogen that result from anaerobic oxidation of ammonium coupled to reduction of iron. We identify a new, autotrophic member of the bacterial order Burkholderiales that may use soil CO2 as a carbon source to couple anaerobic ammonium oxidation and iron reduction. These findings offer insight into the coupled cycles of nitrogen and iron in terrestrial ecosystems and raise questions about the loss of ammonium-nitrogen from arable soils under future climate-change scenarios.

opencc-zeroNov 2020View details →

Data from: Spatial dynamics of alpine treelines under global warming: what explains the mismatch between tree densification and elevational upward shifts at the treeline ecotone?

Aim Most studies focusing on the alpine treeline responses to climate warming have used either the tree densification within the ecotone or its elevational upshift as indicators. However, it is acknowledged that the relation between densification and upshift is spatially heterogeneous, making inferences and comparability among studies tricky. The lack of consistent empirical evidence on this potential mismatch and its drivers leads us to focus on this issue in this study. The aim was twofold: (i) to quantify the mismatch between the two processes at a regional scale, and (ii) to identify its site-specific determinants. Location French eastern Pyrenees Time period 1953-2015 Major taxa studied Pinus uncinata (Ramond ex DC) Methods An object-oriented supervised classification procedure was performed on historical (1953) and current (2015) air-photos. Based on the resulting rasters, densification of the treeline ecotone and upward shift of the treeline were estimated at the two dates in 191 sites, then standardized, before finally being compared. Three site clusters were derived (no mismatch, densification prevalence, upshift prevalence). After having characterized their spatial patterns through join count statistics, a multinomial logistic regression model was computed to identify the correlates of these clusters among a list of site variables. Results No spatial pattern among the categories of responses emerges at a local scale, but buffers with no mismatch tend to aggregate at a larger scale. Changes in minimum air temperatures, site elevation, mean slope, slope morphometry and lithology appear as significant drivers of the observed mismatch, implying that the relation between densification and elevational upshift is context-specific. Main conclusions <a name="_Hlk17817327">Our findings suggest that both </a><a name="_Hlk17816517">densification and upshift </a>should be considered in quantitative analyses of treeline spatial dynamics, since these two ecological processes are not controlled by the same drivers.