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1.
Zootaxa ; 5154(2): 198-210, 2022 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-36095628

RESUMO

A new cladoceran of the faviformis-group of the genus Chydorus Leach, 1816 (Cladocera: Chydoridae), characterized by a honeycomb-like sculpture of valves and head shield, is described from tundra lakes and ponds in North-East Russia. Morphology of the new species was studied using optical and scanning electron microscopy. Chydorus izvekovae sp. nov. differs from all other species of the faviformis-group in a narrow labral keel with elongated apex, and in a greater number of meshes on the valves and head shield. Other species of the faviformis-group in the Western Hemisphere are distributed in the tropical-subtropical zone, they also inhabit mostly shallow waters with well-developed macrophyte zone.


Assuntos
Cladóceros , Poríferos , Distribuição Animal , Estruturas Animais/anatomia & histologia , Animais , Tamanho Corporal , Tamanho do Órgão , Federação Russa , Tundra
2.
Proc Natl Acad Sci U S A ; 119(38): e2118014119, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36095176

RESUMO

Emissions of biogenic volatile organic compounds (BVOCs) are a crucial component of biosphere-atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modeling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain. Here, we show how tundra isoprene emissions respond vigorously to temperature increases, compared to model results. Our unique dataset of direct eddy covariance ecosystem-level isoprene measurements in two contrasting ecosystems exhibited Q10 (the factor by which the emission rate increases with a 10 °C rise in temperature) temperature coefficients of up to 20.8, that is, 3.5 times the Q10 of 5.9 derived from the equivalent model calculations. Crude estimates using the observed temperature responses indicate that tundra vegetation could enhance their isoprene emissions by up to 41% (87%)-that is, 46% (55%) more than estimated by models-with a 2 °C (4 °C) warming. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions.


Assuntos
Ecossistema , Compostos Orgânicos Voláteis , Butadienos , Hemiterpenos , Temperatura , Tundra
3.
Nature ; 608(7923): 546-551, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35948635

RESUMO

Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra1, thereby reducing albedo2-4, altering carbon cycling4 and further changing climate1-4, yet the patterns and processes of this biome shift remain unclear5. Climate warming, required for previous boreal advances6-17, is not sufficient by itself for modern range expansion of conifers forming forest-tundra ecotones5,12-15,17-20. No high-latitude population of conifers, the dominant North American Arctic treeline taxon, has previously been documented5 advancing at rates following the last glacial maximum (LGM)6-8. Here we describe a population of white spruce (Picea glauca) advancing at post-LGM rates7 across an Arctic basin distant from established treelines and provide evidence of mechanisms sustaining the advance. The population doubles each decade, with exponential radial growth in the main stems of individual trees correlating positively with July air temperature. Lateral branches in adults and terminal leaders in large juveniles grow almost twice as fast as those at established treelines. We conclude that surpassing temperature thresholds1,6-17, together with winter winds facilitating long-distance dispersal, deeper snowpack and increased soil nutrient availability promoting recruitment and growth, provides sufficient conditions for boreal forest advance. These observations enable forecast modelling with important insights into the environmental conditions converting tundra into forest.


Assuntos
Aquecimento Global , Picea , Taiga , Temperatura , Árvores , Tundra , Aclimatação , Regiões Árticas , Modelos Climáticos , Aquecimento Global/estatística & dados numéricos , Modelos Biológicos , Picea/crescimento & desenvolvimento , Picea/metabolismo , Estações do Ano , Neve , Solo/química , Árvores/crescimento & desenvolvimento , Árvores/metabolismo , Vento
4.
Commun Biol ; 5(1): 793, 2022 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-35933562

RESUMO

Under climate change, cold-adapted alpine ecosystems are turning into hotspots of warming. However, the complexity of driving forces of growth, associated biomass gain and carbon storage of alpine shrubs is poorly understood. We monitored alpine growth mechanisms of six common shrub species across contrasting biomes, Mediterranean and tundra, using 257 dendrometers, recording stem diameter variability at high temporal resolution. Linking shrub growth to on-site environmental conditions, we modelled intra-annual growth patterns based on distributed lag non-linear models implemented with generalized additive models. We found pronounced bimodal growth patterns across biomes, and counterintuitively, within the cold-adapted biome, moisture, and within the drought-adapted biome, temperature was crucial, with unexpected consequences. In a warmer world, the Mediterranean alpine might experience strong vegetation shifts, biomass gain and greening, while the alpine tundra might see less changes in vegetation patterns, minor modifications of biomass stocks and rather browning.


Assuntos
Ecossistema , Tundra , Biomassa , Mudança Climática , Estações do Ano
5.
FEMS Microbiol Ecol ; 98(8)2022 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-35776963

RESUMO

Due to climate change, increased microbial activity in high-latitude soils may lead to higher greenhouse gas (GHG) emissions. However, microbial GHG production and consumption mechanisms in tundra soils are not thoroughly understood. To investigate how the diversity and functional potential of bacterial and archaeal communities vary across vegetation types and soil layers, we analyzed 116 soil metatranscriptomes from 73 sites in the Finnish sub-Arctic. Meadow soils were characterized by higher pH and lower soil organic matter (SOM) and carbon/nitrogen ratio. By contrast, dwarf shrub-dominated ecosystems had higher SOM and lower pH. Although Actinobacteria, Acidobacteria, Alphaproteobacteria and Planctomycetes were dominant in all communities, there were significant differences at the genus level between vegetation types; plant polymer-degrading groups were more active in shrub-dominated soils than in meadows. Given that climate-change scenarios predict the expansion of shrubs at high latitudes, our results indicate that tundra soil microbial communities harbor potential decomposers of increased plant litter, which may affect the rate of carbon turnover in tundra soils. Additionally, transcripts of methanotrophs were detected in the mineral layer of all soils, which may moderate methane fluxes. This study provides new insights into possible shifts in tundra microbial diversity and activity due to climate change.


Assuntos
Microbiota , Solo , Regiões Árticas , Bactérias/genética , Carbono/análise , Finlândia , Plantas , Solo/química , Microbiologia do Solo , Tundra
6.
Sci Total Environ ; 846: 157385, 2022 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-35870583

RESUMO

The continuous change in observed key indicators such as increasing nitrogen deposition, temperatures and precipitation will have marked but uncertain consequences for the ecosystem carbon (C) sink-source functioning of the Arctic. Here, we use multiple in-situ data streams measured by the Greenland Ecosystem Monitoring programme in tight connection with the Soil-Plant-Atmosphere model and climate projections from the high-resolution HIRHAM5 regional model. We apply this modelling framework with focus on two climatically different tundra sites in Greenland (Zackenberg and Kobbefjord) to assess how sensitive the net C uptake will expectedly be under warmer and wetter conditions across the 21st century and pin down the relative contribution to the overall C sink strength from climate versus plant trait variability. Our results suggest that temperatures (5-7.7 °C), total precipitation (19-110 %) and vapour pressure deficit will increase (32-36 %), while shortwave radiation will decline (6-9 %) at both sites by 2100 under the RCP8.5 scenario. Such a combined effect will, on average, intensify the net C uptake by 9-10 g C m-2 year-1 at both sites towards the end of 2100, but Zackenberg is expected to have more than twice the C sink strength capacity of Kobbefjord. Our sensitivity analysis not only reveals that plant traits are the most sensitive parameters controlling the net C exchange in both sites at the beginning and end of the century, but also that the projected increase in the net C uptake will likely be similarly influenced by future changes in climate and existing local nutrient conditions. A series of experiments forcing realistic changes in plant nitrogen status at both sites corroborates this hypothesis. This work proves the unique synergy between monitoring data and numerical models to assist robust model calibration/validation and narrow uncertainty ranges and ultimately produce more reliable C cycle projections in understudied regions such as Greenland.


Assuntos
Carbono , Ecossistema , Regiões Árticas , Carbono/análise , Mudança Climática , Groenlândia , Nitrogênio/análise , Tundra
7.
PLoS One ; 17(7): e0269938, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35776726

RESUMO

Over the last 60 years, Arctic goose populations have increased while many sympatric tundra nesting bird populations have declined. Hyperabundant geese have well-documented effects on tundra habitats, which can alter habitat use by sympatric bird species. These habitat changes may also alter invertebrate communities and abundances, with potentially important, but as of yet, undocumented effects on insectivorous birds such as shorebirds. Here, we determined the effects of goose-induced habitat alteration on invertebrate communities and relate the observed changes to shorebird diet. At sites and habitat types representing a gradient of goose influence, we identified goose-related changes in ground cover and linked these factors to variation in invertebrate communities. We then used DNA metabarcoding to characterize the diet of six shorebird species across sites and identify inter-site variation in abundance, biomass, and timing of emergence of dominant shorebird prey items. Invertebrate diversity and richness did not vary either among sites or habitat types. However, for prey items identified as part of the shorebird diet, we found significantly higher abundances and biomasses at a moderately goose-influenced site than at either low or high goose-influenced sites. Biomass of Tipulidae, the dominant prey taxon for shorebirds at the study sites, was 7.5 times higher at the moderately goose-influenced site compared to the site where goose influence was minor. We attribute this enhancement of prey biomass to both the fertilizing effect of goose fecal pellets and the moderate grazing pressure. Many studies have documented adverse effects of overabundant geese, but here we show that a moderate degree of goose grazing can lead to enhanced biomass of invertebrates, with the potential for improved shorebird foraging success and chick growth. These benefits, however, might be outweighed by negative effects of goose-induced habitat alteration and predation pressure.


Assuntos
Gansos , Invertebrados , Animais , Dieta/veterinária , Ecossistema , Tundra
8.
Nat Commun ; 13(1): 3843, 2022 07 04.
Artigo em Inglês | MEDLINE | ID: mdl-35788612

RESUMO

Arctic shrub expansion alters carbon budgets, albedo, and warming rates in high latitudes but remains challenging to predict due to unclear underlying controls. Observational studies and models typically use relationships between observed shrub presence and current environmental suitability (bioclimate and topography) to predict shrub expansion, while omitting shrub demographic processes and non-stationary response to changing climate. Here, we use high-resolution satellite imagery across Alaska and western Canada to show that observed shrub expansion has not been controlled by environmental suitability during 1984-2014, but can only be explained by considering seed dispersal and fire. These findings provide the impetus for better observations of recruitment and for incorporating currently underrepresented processes of seed dispersal and fire in land models to project shrub expansion and climate feedbacks. Integrating these dynamic processes with projected fire extent and climate, we estimate shrubs will expand into 25% of the non-shrub tundra by 2100, in contrast to 39% predicted based on increasing environmental suitability alone. Thus, using environmental suitability alone likely overestimates and misrepresents shrub expansion pattern and its associated carbon sink.


Assuntos
Incêndios , Alaska , Regiões Árticas , Mudança Climática , Tundra
9.
PLoS One ; 17(6): e0269801, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35696414

RESUMO

The DeLong Mountain Transportation System (DMTS) haul road links the Red Dog Mine-one of the world's largest zinc mines-with a shipping port on the Chukchi Sea in northwest Alaska, USA. The road traverses 32 km of National Park Service (NPS) lands managed by Cape Krusenstern National Monument (CAKR). Fugitive dusts from ore concentrate transport and mining operations have dispersed zinc (Zn), lead (Pb), cadmium (Cd), and metal sulfides onto NPS lands since the mine began operating in 1989. This study assessed the effects of metal-enriched road dusts on the diversity and community structure of lichens, bryophytes, and vascular plants in dwarf-shrub tundra within CAKR. In a Bayesian posterior predictions model, lichen species richness (LSR) was highly correlated to distance from the haul road and was distributed on the landscape consistently with the spatial patterns of Zn, Pb and Cd patterns published earlier in this journal. The mean modeled LSR of the 3000-4000 m distance class was 41.3, and LSR decreased progressively down to 9.4 species in the 0-50 m class. An ordination of 93 lichen species by 91 plots revealed strong community patterns based on distance from the haul road. The major community gradient was highly correlated (r = 0.99) with LSR and negatively correlated with Cd, Pb and Zn (-0.79 < r < -0.74). Ordinations of bryophyte classes showed less response than lichens to distance from the road and heavy metals values, and vascular plant ordination showed less still. Measures of bryophyte health such as the midrib blackening and frond width of Hylocomium splendens were positively correlated with distance from the haul road and negatively correlated with this same suite of elements. A total area of approximately 55 km2 showed moderate to strong impacts on lichens from fugitive dusts. This is equivalent to an area of almost 1 km on both sides of the haul road running 32 km through CAKR.


Assuntos
Líquens , Metais Pesados , Poluentes do Solo , Alaska , Teorema de Bayes , Cádmio/análise , Poeira/análise , Monitoramento Ambiental , Chumbo , Metais Pesados/análise , Parques Recreativos , Poluentes do Solo/análise , Tundra , Zinco/análise
10.
Glob Chang Biol ; 28(18): 5587-5599, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35748530

RESUMO

Soil carbon (C) is comprised of a continuum of organic compounds with distinct ages (i.e., the time a C atom has experienced in soil since the C atom entered soil). The contribution of different age groups to soil C efflux is critical for understanding soil C stability and persistence, but is poorly understood due to the complexity of soil C pool age structure and potential distinct turnover behaviors of age groups. Here, we build upon the quantification of soil C transit times to infer the age of C atoms in soil C efflux (aefflux ) from seven sequential soil layer depths down to 2 m at a global scale, and compare this age with radiocarbon-inferred ages of C retained in corresponding soil layers (asoil ). In the whole 0-2 m soil profile, the mean aefflux is 194 21 1021 (mean with 5%-95% quantiles) year and is just about one-eighth of asoil ( 1476 717 2547 year), demonstrating that younger C dominates soil C efflux. With increasing soil depth, both aefflux and asoil are increased, but their disparities are markedly narrowed. That is, the proportional contribution of relatively younger soil C to efflux is decreased in deeper layers, demonstrating that C inputs (new and young) stay longer in deeper layers. Across the globe, we find large spatial variability of the contribution of soil C age groups to C efflux. Especially, in deep soil layers of cold regions (e.g., boreal forests and tundra), aefflux may be older than asoil , suggesting that older C dominates C efflux only under a limited range of conditions. These results imply that most C inputs may not contribute to long-term soil C storage, particularly in upper layers that hold the majority of new C inputs.


Assuntos
Carbono , Solo , Carbono/química , Ciclo do Carbono , Compostos Orgânicos , Solo/química , Tundra
11.
Virol J ; 19(1): 99, 2022 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-35659694

RESUMO

BACKGROUND: Mosquito-borne viruses pose a serious threat to humans worldwide. There has been an upsurge in the number of mosquito-borne viruses in Europe, mostly belonging to the families Togaviridae, genus Alphavirus (Sindbis, Chikungunya), Flaviviridae (West Nile, Usutu, Dengue), and Peribunyaviridae, genus Orthobunyavirus, California serogroup (Inkoo, Batai, Tahyna). The principal focus of this study was Inkoo (INKV) and Sindbis (SINV) virus circulating in Norway, Sweden, Finland, and some parts of Russia. These viruses are associated with morbidity in humans. However, there is a knowledge gap regarding reservoirs and transmission. Therefore, we aimed to determine the prevalence of INKV and SINV in blood sucking insects and seroprevalence for INKV in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway. MATERIALS AND METHODS: In total, 213 pools containing about 25 blood sucking insects (BSI) each and 480 reindeer sera were collected in eight Norwegian reindeer summer pasture districts during 2013-2015. The pools were analysed by RT-PCR to detect INKV and by RT-real-time PCR for SINV. Reindeer sera were analysed for INKV-specific IgG by an Indirect Immunofluorescence Assay (n = 480, IIFA) and a Plaque Reduction Neutralization Test (n = 60, PRNT). RESULTS: Aedes spp. were the most dominant species among the collected BSI. Two of the pools were positive for INKV-RNA by RT-PCR and were confirmed by pyrosequencing. The overall estimated pool prevalence (EPP) of INKV in Norway was 0.04%. None of the analysed pools were positive for SINV. Overall IgG seroprevalence in reindeer was 62% positive for INKV by IIFA. Of the 60 reindeer sera- analysed by PRNT for INKV, 80% were confirmed positive, and there was no cross-reactivity with the closely related Tahyna virus (TAHV) and Snowshoe hare virus (SSHV). CONCLUSION: The occurrence and prevalence of INKV in BSI and the high seroprevalence against the virus among semi-domesticated reindeer in Norway indicate that further studies are required for monitoring this virus. SINV was not detected in the BSI in this study, however, human cases of SINV infection are yearly reported from other regions such as Rjukan in south-central Norway. It is therefore essential to monitor both viruses in the human population. Our findings are important to raise awareness regarding the geographical distribution of these mosquito-borne viruses in Northern Europe.


Assuntos
Aedes , Vírus da Encefalite da Califórnia , Flavivirus , Rena , Animais , Vírus da Encefalite da Califórnia/genética , Imunoglobulina G , Noruega/epidemiologia , Estudos Soroepidemiológicos , Vírus Sindbis/genética , Tundra
12.
Sci Rep ; 12(1): 7123, 2022 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-35504957

RESUMO

Beavers were not previously recognized as an Arctic species, and their engineering in the tundra is considered negligible. Recent findings suggest that beavers have moved into Arctic tundra regions and are controlling surface water dynamics, which strongly influence permafrost and landscape stability. Here we use 70 years of satellite images and aerial photography to show the scale and magnitude of northwestward beaver expansion in Alaska, indicated by the construction of over 10,000 beaver ponds in the Arctic tundra. The number of beaver ponds doubled in most areas between ~ 2003 and ~ 2017. Earlier stages of beaver engineering are evident in ~ 1980 imagery, and there is no evidence of beaver engineering in ~ 1952 imagery, consistent with observations from Indigenous communities describing the influx of beavers over the period. Rapidly expanding beaver engineering has created a tundra disturbance regime that appears to be thawing permafrost and exacerbating the effects of climate change.


Assuntos
Lagoas , Roedores , Alaska , Animais , Regiões Árticas , Tundra
13.
Sci Total Environ ; 837: 155783, 2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-35537508

RESUMO

The northernmost regions of our planet experience twice the rate of climate warming compared to the global average. Despite the currently low air temperatures, tundra shrubs are known to exhibit high leaf temperatures and are increasing in height due to warming, but it is unclear how the increase in height will affect the leaf temperature. To study how temperature, soil moisture, and changes in light availability influence the physiology and emissions of climate-relevant volatile organic compounds (VOCs), we conducted a study on two common deciduous tundra shrubs, Salix glauca (separating males and females for potential effects of plant sex) and Betula glandulosa, at two elevations in South Greenland. Low-elevation Salix shrubs were 45% taller, but had 37% lower rates of net CO2 assimilation and 63% lower rates of isoprene emission compared to high-elevation shrubs. Betula shrubs showed 40% higher stomatal conductance and 24% higher glandular trichome density, in the low-elevation valley, compared to those from the high-elevation mountain slope. Betula green leaf volatile emissions were 235% higher at high elevation compared to low elevation. Male Salix showed a distinct VOC blend and emitted 55% more oxygenated VOCs, compared to females, possibly due to plant defense mechanisms. In our light response curves, isoprene emissions increased linearly with light intensity, potentially indicating adaptation to strong light. Leaf temperature decreased with increasing Salix height, at 4 °C m-1, which can have implications for plant physiology. However, no similar relationship was observed for B. glandulosa. Our results highlight that tundra shrub traits and VOC emissions are sensitive to temperature and light, but that local variations in soil moisture strongly interact with temperature and light responses. Our results suggest that effects of climate warming, alone, poorly predict the actual plant responses in tundra vegetation.


Assuntos
Salix , Compostos Orgânicos Voláteis , Regiões Árticas , Betula/fisiologia , Mudança Climática , Solo , Tundra
14.
Sci Total Environ ; 838(Pt 3): 155976, 2022 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-35618134

RESUMO

Over the last decade, an increasing number of studies have used soundscapes to address diverse ecological questions. Sound represents one of the few sources of information capable of providing in situ insights into processes occurring within opaque soil matrices. To date, the use of soundscapes for soil macrofauna monitoring has been experimentally tested only in controlled laboratory environments. Here we assess the validity of laboratory predictions and explore the use of soil soundscape proxies for monitoring soil macrofauna (i.e., earthworm) activities in an outdoor context. In a common garden experiment in northern Sweden, we constructed outdoor mesocosm plots (N = 36) containing two different Arctic vegetation types (meadow and heath) and introduced earthworms to half of these plots. Earthworms substantially altered the ambient soil soundscape under both vegetation types, as measured by both traditional soundscape indices and frequency band power levels, although their acoustic impacts were expressed differently in heath versus meadow soils. While these findings support the as-of-yet untapped promise of using belowground soundscape analyses to monitor soil ecosystem health, direct acoustic emissions from earthworm activities appear to be an unlikely proxy for tracking worm activities at daily timescales. Instead, earthworms indirectly altered the soil soundscape by 're-engineering' the soil matrix: an effect that was dependent on vegetation type. Our findings suggest that long-term (i.e., seasonal) earthworm activities in natural soil settings can likely be monitored indirectly via their impacts on soundscape measures and acoustic indices. Analyzing soil soundscapes may enable larger-scale monitoring of high-latitude soils and is directly applicable to the specific case of earthworm invasions within Arctic soils, which has recently been identified as a potential threat to the resilience of high-latitude ecosystems. Soil soundscapes could also offer a novel means to monitor soils and soil-plant-faunal interactions in situ across diverse pedogenic, agronomic, and ecological systems.


Assuntos
Oligoquetos , Animais , Ecossistema , Espécies Introduzidas , Solo , Tundra
15.
Elife ; 112022 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-35607894

RESUMO

The biodiversity of tundra areas in northern high latitudes is threatened by invasion of forests under global warming. However, poorly understood nonlinear responses of the treeline ecotone mean the timing and extent of tundra losses are unclear, but policymakers need such information to optimize conservation efforts. Our individual-based model LAVESI, developed for the Siberian tundra-taiga ecotone, can help improve our understanding. Consequently, we simulated treeline migration trajectories until the end of the millennium, causing a loss of tundra area when advancing north. Our simulations reveal that the treeline follows climate warming with a severe, century-long time lag, which is overcompensated by infilling of stands in the long run even when temperatures cool again. Our simulations reveal that only under ambitious mitigation strategies (relative concentration pathway 2.6) will ∼30% of original tundra areas remain in the north but separated into two disjunct refugia.


Assuntos
Árvores , Tundra , Mudança Climática , Florestas , Temperatura
16.
Sci Rep ; 12(1): 6796, 2022 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-35474321

RESUMO

The study of local extinction times, together with the associated environmental and human population changes in the last glacial termination, provides insights into the causes of mega- and microfauna extinctions. In East-Central (EC) Europe, groups of Palaeolithic humans were present throughout the last glacial maximum, but disappeared suddenly around 15,200 cal BP. In this study cave sediment profiles dated using radiocarbon techniques and a large set of mammal bones dated directly by AMS 14C were used to determine local extinction times. These were, in turn, compared to changes in the total megafauna population of EC Europe derived from coprophilous fungi, the Epigravettian population decline, quantitative climate models, pollen and plant macrofossil inferred climate, as well as to biome reconstructions. The results suggest that the population size of large herbivores decreased in the area after 17,700 cal BP, when temperate tree abundance and warm continental steppe cover both increased in the lowlands. Boreal forest expansion started around 16,200 cal BP. Cave sediments show the decline of narrow-headed vole and arctic lemming populations specifically associated with a tundra environment at the same time and the expansion of the common vole, an inhabitant of steppes. The last dated appearance of arctic lemming was at ~ 16,640 cal BP, while that of the narrow-headed vole at ~ 13,340, and the estimated extinction time of woolly mammoth was either at 13,830 (GRIWM) or 15,210 (PHASE), and reindeer at 11,860 (GRIWM) or 12,550 cal BP (PHASE). The population decline of the large herbivore fauna slightly preceded changes in terrestrial vegetation, and likely facilitated it via a reduction in the intensity of grazing and the concomitant accumulation of plant biomass. Furthermore, it is possible to conclude that the Late Epigravettian population had high degree of quarry-fidelity; they left the basin when these mammals vanished.


Assuntos
Ecossistema , Mamutes , Animais , Arvicolinae , Clima , Humanos , Mamíferos , Tundra
17.
Ecology ; 103(8): e3734, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35466413

RESUMO

Prey handling processes are considered a dominant mechanism leading to short-term positive indirect effects between prey that share a predator. However, a growing body of research indicates that predators are not necessarily limited by such processes in the wild. Density-dependent changes in predator foraging behavior can also generate positive indirect effects but they are rarely included as explicit functions of prey densities in functional response models. With the aim of untangling proximate mechanisms of species interactions in natural communities and improving our ability to quantify interaction strength, we extended the multi-prey version of the Holling disk equation by including density-dependent changes in predator foraging behavior. Our model, based on species traits and behavior, was inspired by the vertebrate community of the arctic tundra, where the main predator (the arctic fox) is an active forager feeding primarily on cyclic small rodent (lemming) and eggs of various tundra-nesting bird species. Short-term positive indirect effects of lemmings on birds have been documented over the circumpolar Arctic but the underlying mechanisms remain poorly understood. We used a unique data set, containing high-frequency GPS tracking, accelerometer, behavioral, and experimental data to parameterize the multi-prey model, and a 15-year time series of prey densities and bird nesting success to evaluate interaction strength between species. We found that (1) prey handling processes play a minor role in our system and (2) changes in arctic fox daily activity budget and distance traveled can partly explain the predation release on birds observed during lemming peaks. These adjustments in predator foraging behavior with respect to the main prey density thus appear as the dominant mechanism leading to positive indirect effects commonly reported among arctic tundra prey. Density-dependent changes in functional response components have been little studied in natural vertebrate communities and deserve more attention to improve our ability to quantify the strength of species interactions.


Assuntos
Comportamento Predatório , Tundra , Animais , Regiões Árticas , Arvicolinae/fisiologia , Aves/fisiologia , Raposas/fisiologia , Dinâmica Populacional
18.
Oecologia ; 198(4): 1073-1084, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35426519

RESUMO

Intra- and inter-specific resource partitioning within predator communities is a fundamental component of trophic ecology, and one proposed mechanism for how populations partition resources is through individual niche variation. The Niche Variation Hypothesis (NVH) predicts that inter-individual trait variation leads to functional trade-offs in foraging efficiency, resulting in populations composed of individual dietary specialists. The degree to which niche specialization persists within a population is plastic and responsive to fluctuating resource availability. We quantified niche overlap and tested the NVH within an Arctic raptor guild, focusing on three species that employ different foraging strategies: golden eagles (generalists); gyrfalcons (facultative specialists); and rough-legged hawks (specialists). Tundra ecosystems exhibit cyclic populations of arvicoline rodents (lemmings and voles), providing a unique system in which to examine predator diet in response to interannual fluctuations in resource availability. Using blood δ13C and δ15N values from 189 raptor nestlings on Alaska's Seward Peninsula (2014-2019), we calculated isotopic niche width and used Bayesian stable isotope mixing models (BSIMMs) to characterize individual specialization and test the NVH. Nest-level specialization estimated from stable isotopes was strongly correlated with indices of specialization based on camera trap data. We observed a high degree of isotopic niche overlap between the three species and gyrfalcons displayed a positive relationship between individual specialization and population niche width on an interannual basis consistent with the NVH. Our findings suggest plasticity in niche specialization may reduce intra- and inter-specific resource competition under dynamic ecological conditions.


Assuntos
Ecossistema , Aves Predatórias , Animais , Regiões Árticas , Arvicolinae , Teorema de Bayes , Tundra
19.
Sci Total Environ ; 835: 155495, 2022 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-35472357

RESUMO

Poikilohydric autotrophs are the main colonizers of the permanent ice-free areas in the Antarctic tundra biome. Global climate warming and the small human footprint in this ecosystem make it especially vulnerable to abrupt changes. Elucidating the effects of climate change on the Antarctic ecosystem is challenging because it mainly comprises poikilohydric species, which are greatly influenced by microtopographic factors. In the present study, we investigated the potential effects of climate change on the metabolic activity and net primary photosynthesis (NPP) in the widespread lichen species Usnea aurantiaco-atra. Long-term monitoring of chlorophyll a fluorescence in the field was combined with photosynthetic performance measurements in laboratory experiments in order to establish the daily response patterns under biotic and abiotic factors at micro- and macro-scales. Our findings suggest that macroclimate is a poor predictor of NPP, thereby indicating that microclimate is the main driver due to the strong effects of microtopographic factors on cryptogams. Metabolic activity is also crucial for estimating the NPP, which is highly dependent on the type, distribution, and duration of the hydration sources available throughout the year. Under RCP 4.5 and RCP 8.5, metabolic activity will increase slightly compared with that at present due to the increased precipitation events predicted in MIROC5. Temperature is highlighted as the main driver for NPP projections, and thus climate warming will lead to an average increase in NPP of 167-171% at the end of the century. However, small changes in other drivers such as light and relative humidity may strongly modify the metabolic activity patterns of poikilohydric autotrophs, and thus their NPP. Species with similar physiological response ranges to the species investigated in the present study are expected to behave in a similar manner provided that liquid water is available.


Assuntos
Líquens , Unionidae , Animais , Clorofila A , Mudança Climática , Ecossistema , Humanos , Líquens/fisiologia , Fotossíntese , Tundra
20.
Sci Total Environ ; 835: 155449, 2022 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-35483473

RESUMO

Carbon tetrachloride (CCl4) is an anthropogenic gas with a long atmospheric lifetime and can catalyze the destruction of stratospheric ozone. Natural soils are believed to be important and widespread sinks of atmospheric CCl4, although poorly characterized due to a limited number of measurements. In this study, for the first time in situ static-chamber measurements and laboratory-based incubations for CCl4 fluxes were conducted at coastal Antarctic tundra. Results showed that soil in remote Antarctica is also acting as a CCl4 sink, with an average uptake rate of -2.2 ± 0.6 nmol m-2 d-1, which is comparable to the reported soil sinks in other regions of the world. No significant difference (p > 0.05) was found across different types of tundra, such normal upland tundra, coastal marsh tundra, and tundra in the sea animal colonies. Soil CCl4 fluxes did not show significant correlations (p > 0.05) with soil moisture, pH, TOC, TN, TP and Cl contents. Laboratory-based anoxic incubations showed that the uptake rates of CCl4 in tundra soil were suppressed; post-thermal sterilization incubations showed that soil CCl4 sink was enhanced; these results suggested that CCl4 degradation in tundra soil was likely an abiotic process preferring oxic environments. A rough extrapolation suggested that Antarctic tundra may degrade about 2.4 metric tons of atmospheric CCl4 each year. Combining soil CCl4 fluxes from this study and other literature reports, CCl4 partial lifetime with respect to the soil sink was evaluated to be 354 (235-474) years, which supported the recent viewpoint that the soil sink of CCl4 is smaller than previously thought.


Assuntos
Ecossistema , Solo , Animais , Regiões Antárticas , Solo/química , Tundra , Áreas Alagadas
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