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133 results for “ecotone”
Data from: Contrasting species decline but high sensitivity to increasing water stress on a mixed pine-oak ecotone
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Local adaptation in thermal tolerance for a tropical butterfly across ecotone and rainforest habitats
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Warming and reduced rainfall alter fungal necromass decomposition rates and associated microbial community composition and functioning at a temperate-boreal forest ecotone
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Ecotone might provide key refugium for sky island mammals in the Southern Appalachian Mountains
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Tree biomass does not correlate with soil carbon stocks in forest-tundra ecotones along a 1100 km latitudinal gradient in Norway
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Data from: Unraveling the taxonomic, functional and phylogenetic diversity of lizard assemblages in riparian forest areas in the Amazon–Pantanal ecotone
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Data for: Responses of soil phosphorus cycling and bioavailability to plant invasion in river-lake ecotones
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Tree Rings, Englund Ecotone Scientific and Natural Area, Minnesota
Both increases in temperature and changes in precipitation may limit future tree growth, but rising atmospheric CO2 could offset some of these stressors through increased plant Water Use Efficiency (WUE). The net balance between the negative impacts of climate change and positive effects of CO2 on tree growth will be most important for systems already at plant physiological limits, where increased climate stress could drive mortality and shifts in range distribution. Here, we quantify the effects of climate, stand structure, and rising CO2 on both annual tree-ring growth increment and WUE at a savanna-forest boundary in the Upper Midwest United States. Taking a Bayesian hierarchical modelling approach, we find that plant WUE increased by ~13-25% over the course of the 20th century, but on average, tree-ring growth increments do not significantly increase. Consistent with higher WUE under increased CO2 and recent wetting, we observe a decrease in sensitivity of tree growth to annual precipitation, leading to 25-65% higher growth under dry conditions compared to trees of similar age and size in the past. However, an emerging interaction between summer maximum temperatures and annual precipitation diminishes the water-savings benefit under hot and dry conditions. Both the decrease in precipitation sensitivity, and the interaction between temperature and precipitation are strongest in open canopy microclimates, suggesting that stand structure may modulate response to future changes. Overall, we find that while higher WUE may provide some water savings benefits to growth under normal drought conditions, near-term future temperature increases combined with drought events could drive growth declines of over 50%. These products are used in the manucript, Heilman et al., 2020, Increased water use efficiency leads to decreased precipitation sensitivity of tree growth, but is offset by high temperatures. Submitted for review. The tree rings in this data package and those in ms
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?
<p><b>Aim</b></p> <p>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.</p> <p><b>Location</b></p> <p>French eastern Pyrenees</p> <p><b>Time period</b></p> <p>1953-2015</p> <p><b>Major taxa studied </b></p> <p><i>Pinus</i><i> uncinata </i>(Ramond ex DC)</p> <p><b>Methods</b></p> <p>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.</p> <p><b>Results</b></p> <p>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.</p> <p><b>Main conclusions</b></p> <p><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.</p>
Data from: Reproduction as a bottleneck to treeline advance across the circumarctic forest tundra ecotone
The fundamental niche of many species is shifting with climate change, especially in sub-arctic ecosystems with pronounced recent warming. Ongoing warming in sub-arctic regions should lessen environmental constraints on tree growth and reproduction, leading to increased success of trees colonising tundra. Nevertheless, variable responses of treeline ecotones have been documented in association with warming temperatures. One explanation for time lags between increasingly favourable environmental conditions and treeline ecotone movement is reproductive limitations caused by low seed availability. Our objective was to assess the reproductive constraints of the dominant tree species at the treeline ecotone in the circumpolar north. We sampled reproductive structures of trees (cones and catkins) and stand attributes across circumarctic treeline ecotones. We used generalized linear mixed models to estimate the sensitivity of seed production and the availability of viable seed to regional climate, stand structure, and species-specific characteristics. Both seed production and viability of available seed were strongly driven by specific, sequential seasonal climatic conditions, but in different ways. Seed production was greatest when growing seasons with more growing degree days coincided with years with high precipitation. Two consecutive years with more growing degree days and low precipitation resulted in low seed production. Seasonal climate effects on the viability of available seed depended on the physical characteristics of the reproductive structures. Large-coned and -seeded species take more time to develop mature embryos and were therefore more sensitive to increases in growing degree days in the year of flowering and embryo development. Our findings suggest that both moisture stress and abbreviated growing seasons can have a notable negative influence on the production and viability of available seed at treeline. Our synthesis revealed that constraints on predispersal reproduction within the treeline ecotone might create a considerable time lag for range expansion of tree populations into tundra ecosystems.
Data from: Decay of ecosystem differences and decoupling of tree community-soil environment relationships at ecotones
Ecotones are important landscape features where there is a transition between adjoining ecosystems. However, there are few generalized hypotheses about the response of communities to ecotones, except for a proposed increase in species richness that receives varying empirical support. Based on the assumption that transport of abiotic material and dispersal of organism propagules across ecotones are independent processes, we propose the new hypothesis that ecotones decouple community-environment relationships, increasing the importance of spatial structure that is independent of the environment. We tested this hypothesis by examining the effects of ecotones on relationships between trees and soil properties in a temperate deciduous forest. The study area included different landforms defined by topography, hydrology, and geomorphology, which we designated upland, bottomland, and riparian forests. The site also included a mowed herbaceous corridor. We found that soil properties and tree community composition significantly differed among landforms, and thus they could be treated as differing ecosystem types. However, inclusion of plots near ecotones significantly reduced the variance explained by landform due to introduction of increased noise, increased similarity of ecotone plots in different landforms, or both. To examine tree community-soil environment relationships, factorial kriging analysis was used to decompose variation in soil properties into structures associated with differing spatial scales, which were then used as predictors of tree composition using redundancy analysis. In agreement with the ecotone-decoupling hypothesis, we found that ecotones introduced significant unexplained variation into correlations between tree community composition and soil properties. In addition, spatial variation in tree community composition that was independent of soil properties was only detected when ecotones were included in the analysis, and little variation in tree community composition was attributed to small-scale soil property structures. Together, these results indicate that dispersal limitation and mass effects in the tree community take on increased importance near ecotones. We found no consistent changes in tree species richness associated with ecotones, and suggest that the ecotone-decoupling hypothesis may correspond with a more general community-level pattern that warrants further testing. Decoupling of community-environment relationships near ecotones also has important implications for accuracy of models predicting community distributions from abiotic information.
Data from: Ecophysiological variation across a forest-ecotone gradient produces divergent climate change vulnerability within species
Climate change related risks and impacts on ectotherms will be mediated by habitats and their influence on local thermal environments. While many studies have documented morphological and genetic aspects of niche divergence across habitats, few have examined thermal performance across such gradients and directly linked this variation to contemporary climate change impacts. In this study, we quantified variation in thermal performance across a gradient from forest to gallery forest-savanna mosaic in Cameroon for a skink species (Trachylepis affinis) known to be diverging genetically and morphologically across that habitat gradient. Based on these results, we then applied a mechanistic modelling approach (NicheMapR) to project changes in potential activity, as constrained by thermal performance, in response to climate change. As a complimentary approach, we also compared mechanistic projections with climate-driven changes in habitat suitability based on species distribution models of forest and ecotone skinks. We found that ecotone skinks may benefit from warming and experience increased activity while forest skinks will likely face a drastic decrease in thermal suitability across the forest zone. Species distribution models projected that thermal suitability for forest skinks in coastal forests would decline but in other parts of the forest zone skinks are projected to experience increased thermal suitability. The results here highlight the utility of mechanistic approaches in revealing and understanding patterns of climate change vulnerability which may not be detected with species distribution models alone. This study also emphasizes the importance of intra-specific physiological variation, and habitat-specific thermal performance relationships in particular, in determining warming responses.
Data from: Survival by genotype: patterns at Mc1r are not black and white at the White Sands ecotone
Measuring links among genotype, phenotype and survival in the wild has long been a focus of studies of adaptation. We conducted a 4-year capture–recapture study to measure survival by genotype and phenotype in the Southwestern Fence Lizard (Sceloporus cowlesi) at the White Sands ecotone (transition area between white sands and dark soil habitats). We report several unanticipated findings. First, in contrast with previous work showing that cryptic blanched coloration in S. cowlesi from the heart of the dunes is associated with mutations in the melanocortin-1 receptor gene (Mc1r), ecotonal S. cowlesi showed minimal association between colour phenotype and Mc1r genotype. Second, the frequency of the derived Mc1r allele in ecotonal S. cowlesi appeared to decrease over time. Third, our capture–recapture data revealed a lower survival rate for S. cowlesi individuals with the derived Mc1r allele. Thus, our results suggest that selection at the ecotone may have favoured the wild-type allele in recent years. Even in a system where a genotype–phenotype association appeared to be black and white, our study suggests that additional factors – including phenotypic plasticity, epistasis, pleiotropy and gene flow – may play important roles at the White Sands ecotone. Our study highlights the importance of linking molecular, genomic and organismal approaches for understanding adaptation in the wild. Furthermore, our findings indicate that dynamics of natural selection can be particularly complex in transitional habitats like ecotones and emphasize the need for future research that examines the patterns of ongoing selection in other ecological 'grey' zones.
Data from: Metabolic traits of westslope cutthroat, introduced rainbow trout and their hybrids in an ecotonal hybrid zone along an elevation gradient
In the Upper Oldman River, Alberta, introduced non-native hatchery rainbow trout hybridize with native westslope cutthroat trout, resulting in a hybrid swarm. Rainbow trout dominate at low elevations (<1250 m) in the river mainstem, cutthroat in high elevation tributaries (>1400 m), and hybrids are numerically dominant in the mid-elevation range. We hypothesized that metabolism of rainbow trout would exceed that of cutthroat trout, and that the elevation gradient in genetic makeup would be mirrored by a gradient in metabolic traits, with intermediate traits in the hybrid dominated ecotone. Metabolic traits were measured and regressed against the genetic makeup of individuals and elevation. Rainbow trout had higher oxygen consumption rates (OCR), higher white muscle lactate dehydrogenase (LDH) and citrate synthase (CS) activity, and higher plasma acetylcholinesterase (AchE) than cutthroat trout. Hybrids had intermediate OCR and AchE, but LDH activity as high as rainbow trout. While hybrid zones are usually modeled as a balance between cross species mating and selection against hybrids, ecotonal hybrid zones, where hybrids proliferate in intermediate habitats and have traits that appear well suited to ecotonal conditions, have been proposed for some plants and animals, and may have important implications for resource management and conservation.
Data from:Intraspecific variability improves environmental matching, but does not increase ecological breadth along a wet-to-dry ecotone
It is widely assumed that higher levels of intraspecific variability in one or more traits should allow species to persist under a wider range of environmental conditions. However, few studies have examined whether species that exhibit high variability are found in a wider range of environmental conditions, and whether variability increases the ability of a species to adapt to prevailing ecological gradients. We used four plant functional traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N) and maximum plant height in 49 species across a strong environmental gradient to answer three questions: 1) is there evidence for 'high-variability' species (that is, species which show high variability in multiple traits, simultaneously)? 2) are species with more variable traits present across a wider range of environmental conditions than less variable species? And 3) whether more variable species show better trait-environment matching to the prevailing abiotic (soil moisture) gradient at the site? We found little evidence for a 'high-variability' species. Variability was correlated for two leaf traits, SLA and LDMC, while variability in leaf traits and plant height were not correlated. We found little evidence that more variable species were present in more diverse conditions: only variation in SLA was correlated with a wider ecological niche breadth. For plant traits along the soil-moisture gradient, higher variability led to better trait-environment matching in half of measured traits. Overall, we found little support for the existence of 'high-variability' species, but that variability in SLA is correlated with a wider ecological breadth. We also found evidence that variation in traits can improve trait-environment matching, a relationship which may facilitate our understanding ecological breadth along prevailing gradients, and community assembly on the basis of traits.
Data from: Riverscape genetics identifies replicated ecological divergence across an Amazonian ecotone
Ecological speciation involves the evolution of reproductive isolation and niche divergence in the absence of a physical barrier to gene flow. The process is one of the most controversial topics of the speciation debate, particularly in tropical regions. Here, we investigate ecologically based divergence across an Amazonian ecotone in the electric fish, Steatogenys elegans. We combine phylogenetics, genome scans, and population genetics with a recently developed individual-based evolutionary landscape genetics approach that incorporates selection. This framework is used to assess the relative contributions of geography and divergent natural selection between environments as biodiversity drivers. We report on two closely related and sympatric lineages that exemplify how divergent selection across a major Amazonian aquatic ecotone (i.e., between rivers with markedly different hydrochemical properties) may result in replicated ecologically mediated speciation. The results link selection across an ecological gradient with reproductive isolation and we propose that assortative mating based on water color may be driving the divergence. Divergence resulting from ecologically driven selection highlights the importance of considering environmental heterogeneity in studies of speciation in tropical regions. Furthermore, we show that framing ecological speciation in a spatially explicit evolutionary landscape genetics framework provides an important first step in exploring a wide range of the potential effects of spatial dependence in natural selection.
Data from: Carbon isotopes of C3 herbs correlate with temperature on removing the influence of precipitation across a temperature transect in the agro-pastoral ecotone of Northern China
Plant δ13C–temperature (δ-T) relation has been established in many systems and is often used as paleotemperature transfer function. However, it is still unclear about the exact contributions of temperature variation to plant 13C discrimination because of covariation between temperature and precipitation (aridity), which reduces confidence in reconstruction of paleoclimate. In this study, we measured carbon isotope composition (δ13C) of 173 samples of C3 perennial herbs from 22 sites across a temperature gradient along the 400 mm isohyet in the farming-pastoral zone of North China. The results showed that precipitation obviously affected the correlations of temperatures and foliar δ13C. After removing the influence of precipitation by analysis of covariance (ANCOVA), a more strongly positive relationship was obtained between site-mean foliar δ13C and annual mean temperature (AMT), with a regression coefficient of 0.1636‰/°C (p = .0024). For widespread species, Artemisia lavandulaefolia and Artemisia capillaries, the slopes (or coefficients) of foliar δ13C and AMT were significantly steeper (larger) than those of foliar δ13C and AMT where the precipitation influence was not excluded, whereas the δ-T coefficients of Polygonum persicaria and Leymus chinensis showed little change across the transect after deducting the precipitation effect. Moreover, the positive relationship between temperature and δ13C over the transect could be explained by soil moisture availability related to temperature. Our results may afford new opportunities for investigating the nature of past climate variability.
Data from: Dynamics of marsh-mangrove ecotone since the mid-Holocene: a palynological study of mangrove encroachment and sea level rise in the Shark River Estuary, Florida
Sea level rise and the associated inland shift of the marsh-mangrove ecotone in south Florida have raised many scientific and management concerns in recent years. Holocene paleoecological records can provide an important baseline to shed light on the long-term dynamics of vegetation changes across this ecotone in the past, which is needed to predict the future. In this study, we present palynological, X-ray fluorescence, and loss-on ignition data from four sedimentary cores recovered from a 20-km marine-to-freshwater transect along the Shark River Estuary, southwest Everglades, to document the patterns and processes of coastal vegetation changes in response to sea level rise since the mid-Holocene. Our record indicates that freshwater marsh progressively replaced marl prairies at the Shark River Estuary between 5700 and 4400 cal yr BP. As marine transgression continued, marine influence reached the threshold necessary for mangroves to establish at the current mouth of the Shark River Slough at 3800 cal yr BP. During the next 3000 years, although sea level rise in the Western North Atlantic slowed down to 0.4 mm/yr, a spatial and temporal gradient was evident as the marsh-mangrove ecotone shifted inland by 20 km from 3800 to 800 cal yr BP, accompanied by a gradual landward replacement of freshwater marsh by mangrove forest. If sea level continues to rise at 2.33 mm/yr in the 21st century in south Florida, it is possible that marine influence will reach the threshold for mangroves to establish in the central Everglades, and we could expect a much more aggressive mangrove encroachment toward the northern and interior parts of south Florida in the next few centuries.
Fig. 2. Climogram showing average month temperature and rainfall from June 1996 in Aquatic Coleoptera In The Subtropical-Pampasic Ecotone (Argentina, Buenos Aires): Species Composition And Temporal Changes
Fig. 2. Climogram showing average month temperature and rainfall from June 1996 to July 1998 (Data from Estación Meteorológica La Plata, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata).
Subspecies and Distribution. P. g. gymnocercus Fischer, 1814 — subtropical grasslands of NE Argentina, SE Brazil, Paraguay, and Uruguay. Pg. antiquus Ameghino, 1889 — Pampas grasslands, monte scrublands, and open woodlands of C Argentina. P. g. lordi Massoia, 1982 — Chaco-montane tropical forest ecotone in NW Argentina (Salta & Jujuy Provinces). The subspecific status of the Pampas Fox from Entre Rios Province in Argentina remains unclear, and there are no data regarding the taxonomic position of Bolivian foxes. in Canidae
Subspecies and Distribution. P. g. gymnocercus Fischer, 1814 — subtropical grasslands of NE Argentina, SE Brazil, Paraguay, and Uruguay. Pg. antiquus Ameghino, 1889 — Pampas grasslands, monte scrublands, and open woodlands of C Argentina. P. g. lordi Massoia, 1982 — Chaco-montane tropical forest ecotone in NW Argentina (Salta & Jujuy Provinces). The subspecific status of the Pampas Fox from Entre Rios Province in Argentina remains unclear, and there are no data regarding the taxonomic position of Bolivian foxes.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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