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0000-0002-8994-9305
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Simon Fraser University
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Polar Knowledge Canada
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Publications
Adaptations of a native Subantarctic flightless fly to dehydration stress: more plastic than we thought? ( Short Communication)
Publisher: Masaryk University Press
Date: 06-2014
DOI: 10.5817/CPR2014-2-12
Abstract: Water conservation is a critical aspect affecting the survival, distribution and abundance of terrestrial arthropods. In this study we investigate mechanisms of dehydration tolerance of the native, flightless fly, Calycopteryx moseleyi, inhabiting contrasting environments at two localities in the Kerguelen Islands. We compare the survival abilities and management of body water content of adult flies from two different ecophenotypes when exposed to conditions of low relative humidity. Our results suggest a broad plasticity in the responses of C. moseleyi to desiccation, showing distinct local adaptations to environmental conditions.
Forage selection by collared pikas,Ochotona collaris, under varying degrees of predation risk
Publisher: Canadian Science Publishing
Date: 04-2004
DOI: 10.1139/Z04-024
Abstract: The effects of predation risk on foraging behavior often result in a trade-off between obtaining food and seeking shelter and may alter the selectivity of herbivores for in idual plant species. We experimentally measured forage selection by a small alpine herbivore, the collared pika (Ochotona collaris (Nelson, 1893)), using a cafeteria-style arrangement of six potential forage species at five levels of predation risk. Contrary to our prediction, haying pikas did not switch preferences for forage species of different nutritional quality as predation risk increased. However, the total amount of forage removed was inversely related to risk, and the addition of cover at treatments of greatest potential risk ameliorated the negative effects of higher predation risk. The reasons for increased preference for poorer quality forage species in 2002 relative to 2000 are currently unknown but may reflect changes in predator abundance, forage quality, or increased competition for limited forage resources.
Higher predation risk for insect prey at low latitudes and elevations.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-05-2017
Abstract: Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.
Estimating Temperature Fields from MODIS Land Surface Temperature and Air Temperature Observations in a Sub-Arctic Alpine Environment
Publisher: MDPI AG
Date: 24-01-2014
DOI: 10.3390/RS6020946
Variability, contingency and rapid change in recent subarctic alpine tree line dynamics
Publisher: Wiley
Date: 12-02-2007
When? Where? and for How Long? Census Design Considerations for an Alpine Lagomorph, the Collared Pika (Ochotona collaris)
Publisher: Springer Berlin Heidelberg
Date: 2008
IPY 2007–08 and the Resurgence of Northern (& Polar) Research in Canada
Publisher: The Arctic Institute of North America
Date: 27-01-2010
DOI: 10.14430/ARCTIC401
THE IMPACT OF PREDATOR-INDUCED STRESS ON THE SNOWSHOE HARE CYCLE
Publisher: Wiley
Date: 08-2019
Plot-scale evidence of tundra vegetation change and links to recent summer warming
Publisher: Springer Science and Business Media LLC
Date: 08-04-2012
DOI: 10.1038/NCLIMATE1465
Putting the Canadian Polar House in Order
Publisher: The Arctic Institute of North America
Date: 2004
DOI: 10.14430/ARCTIC488
Evaluating Cloud Contamination in Clear-Sky MODIS Terra Daytime Land Surface Temperatures Using Ground-Based Meteorology Station Observations
Publisher: American Meteorological Society
Date: 27-02-2013
DOI: 10.1175/JCLI-D-12-00250.1
Abstract: Environment Canada meteorological station hourly s led air temperatures Tair at four stations in the southwest Yukon were used to identify cloud contamination in the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra clear-sky daytime land surface temperature (LST) and emissivity daily level-3 global 1-km grid product (MOD11A1, Collection 5) that is not flagged by the MODIS quality algorithm as contaminated. The additional cloud masking used qualitative ground-based sky condition observations, collected at two of the four stations, and coincident MODIS quality flag information. The results indicate that air temperature observed at a variety of discrete spatial locations having different land cover is highly correlated with MODIS LST collected at 1-km grid spacing. Quadratic relationships between LST and air temperature, constrained by ground observations of “clear” sky conditions, show less variability than relationships found under “mainly clear” and “mostly cloudy” sky conditions, and the more clouds observed in the sky coincides with a decreasing y intercept. Analysis of MODIS LST and its associated quality flags show a cold bias (& °C) in the assignment of the ≤3-K-average LST error, indicating MODIS LST has a maximum average error of ≤2 K over a warm surface (& °C). Analysis of two observation stations shows that unidentified clouds in MODIS LST are between 13% and 17%, a result that agrees well with previous studies. Analysis of daytime values is important because many processes are dependent on daylight and maximum temperature. The daytime clear-sky LST–Tair relationship observed for the good-quality confirmed cloud-free-sky MODIS LST quality flag can be used to discriminate cloud-contaminated grid cells beyond the standard MODIS cloud mask.
The impacts of climate change on circumpolar biodiversity
Publisher: Informa UK Limited
Date: 09-2012
Evidence for Elevation-Dependent Warming in the St. Elias Mountains, Yukon, Canada
Publisher: American Meteorological Society
Date: 15-04-2020
Abstract: The climate of high midlatitude mountains appears to be warming faster than the global average, but evidence for such elevation-dependent warming (EDW) at higher latitudes is presently scarce. Here, we use a comprehensive network of remote meteorological stations, proximal radiosonde measurements, downscaled temperature reanalysis, ice cores, and climate indices to investigate the manifestation and possible drivers of EDW in the St. Elias Mountains in subarctic Yukon, Canada. Linear trend analysis of comprehensively validated annual downscaled North American Regional Reanalysis (NARR) gridded surface air temperatures for the years 1979–2016 indicates a warming rate of 0.028°C a −1 between 5500 and 6000 m above mean sea level (MSL), which is ~1.6 times larger than the global-average warming rate between 1970 and 2015. The warming rate between 5500 and 6000 m MSL was ~1.5 times greater than the rate at the 2000–2500 m MSL bin (0.019°C a −1 ), which is similar to the majority of warming rates estimated worldwide over similar elevation gradients. Accelerated warming since 1979, measured by radiosondes, indicates a maximum rate at 400 hPa (~7010 m MSL). EDW in the St. Elias region therefore appears to be driven by recent warming of the free troposphere. MODIS satellite data show no evidence for an enhanced snow albedo feedback above 2500 m MSL, and declining trends in sulfate aerosols deposited in high-elevation ice cores suggest a modest increase in radiative forcing at these elevations. In contrast, increasing trends in water vapor mixing ratio at the 500-hPa level measured by radiosonde suggest that a longwave radiation vapor feedback is contributing to EDW.
Patterns of decadal, seasonal and daily visitation to mineral licks, a critical resource hotspot for mountain goats Oreamnos americanus in the Rocky Mountains
Publisher: Wiley
Date: 12-11-2020
DOI: 10.2981/WLB.00736
Abstract: Concentrated resources or hotspots, within an in idual's usual home range may be strong determinates of movement behavior. We evaluated the patterns of mineral lick use by a population of mountain goats Oreamnos americanus displaying high site fidelity at two mineral licks along the Trans‐Canada Highway in the Rocky Mountains, British Columbia, Canada. Access to these mineral licks was characterized by deliberate and repetitive movements into marginal habitat. We describe the patterns of mineral lick use over decadal, seasonal and daily periods by using dendrochronological analysis of tr ling scars along mountain goat trails, movements determined from GPS collar locations, and camera traps placed along trails and at mineral licks, respectively. Our findings suggest that mountain goats have strong trans‐generational behavioral traditions and that they predictably access mineral licks using the same trails, seasons and daily patterns. Differences in the patterns of mineral lick visitation between males and females may be related to reproductive and nutritional status, while their nocturnal use appears to be a response to disturbance at the mineral licks. Understanding how animals adjust their behavior in response to highly localized resource hotspots outside their usual home range can provide valuable information for the management of these critical habitat features and the wider conservation of mountain goat populations.
Spring warming in Yukon mountains is not amplified by the snow albedo feedback
Publisher: Springer Science and Business Media LLC
Date: 13-06-2018
DOI: 10.1038/S41598-018-27348-7
Abstract: Decreasing spring snow cover may lify Arctic warming through the snow albedo feedback. To examine the impact of snowmelt on increasing temperature we used a 5,000 m elevation gradient in Yukon, Canada, extending from valley-bottom conifer forests, through middle elevation tundra, to high elevation icefields, to compare validated downscaled reanalysis air temperature patterns across elevational bands characterized by different patterns of spring snowmelt. From 2000 to 2014 we observed surface warming of 0.01 °C/a·1,000 m in May (0.14 °C/a at 1,000 m to 0.19 °C/a at 5,000 m), and uniform cooling of 0.09 °C/a in June at all elevations. May temperature trends across elevationally dependent land cover types were highly correlated with each other despite large variations in albedo and snow cover trends. Furthermore, a clear dependency of infrared skin temperature on snow cover mediated albedo decline was observed in tundra, but this was insufficient to influence average diurnal air temperature. We observed negative June temperature trends which we attribute to increasing daytime cloud cover because albedo and snow cover trends were unchanging. We conclude that 8-day and monthly averaged Spring air temperature trends are responding to a synoptic external forcing that is much stronger than the snow albedo feedback in sub-Arctic mountains.
UNDERSTANDING EARTH’S POLAR CHALLEN-GES: INTERNATIONAL POLAR YEAR 2007–2008. Igor Krupnik, Ian Allison, Robin Bell, Paul Cutler, David Hik, Jerónimo López-Martínez, Volker Rachold, Eduard Sarukhanian
Publisher: Cambridge University Press (CUP)
Date: 03-02-2015
Flower‐visitor communities of an arcto‐alpine plant—Global patterns in species richness, phylogenetic diversity and ecological functioning
Publisher: Wiley
Date: 07-12-2018
DOI: 10.1111/MEC.14932
Microtopographic patterns in an arctic baydjarakh field: do fine-grain patterns enforce landscape stability?
Publisher: IOP Publishing
Date: 04-01-2012
Ecological, Evolutionary and Social Constraints on Reproductive Effort: Are Hoary Marmots Really Biennial Breeders?
Publisher: Public Library of Science (PLoS)
Date: 13-03-2015
Winter weather versus group thermoregulation: what determines survival in hibernating mammals?
Publisher: Springer Science and Business Media LLC
Date: 03-03-2013
DOI: 10.1007/S00442-013-2612-0
Abstract: For socially hibernating mammals, the effectiveness of huddling as a means of energy conservation should increase with group size. However, group size has only been linked to increased survival in a few hibernating species, and the relative importance of social structure versus winter conditions during hibernation remains uncertain. We studied the influence of winter weather conditions, social group composition, age-structure, and other environmental factors and in idual attributes on the overwinter survival of hoary marmots (Marmota caligata) in the Yukon Territory, Canada. Juvenile hoary marmot survival was negatively correlated with the mean winter (November to May) Pacific Decadal Oscillation (PDO) index. Survival in older age-classes was negatively correlated with PDO lagged by 1 year. Social group size and structure were weakly correlated with survival in comparison to PDO. The relationship between winter PDO and survival was most likely due to the importance of snowpack as insulation during hibernation. The apparent response of hoary marmots to changing winter conditions contrasted sharply with those of other marmot species and other mammalian alpine herbivores. In conclusion, the severity of winter weather may constrain the effectiveness of group thermoregulation in socially hibernating mammals.
Is dimethylsulfoxide a reliable solvent for extracting chlorophyll under field conditions?
Publisher: Springer Science and Business Media LLC
Date: 2003
Social structure and facultative mating systems of hoary marmots (Marmota caligata)
Publisher: Wiley
Date: 31-01-2007
Predicting Effects of Predation on Conservation of Endangered Prey
Publisher: Wiley
Date: 17-06-1998
Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow–shrub interactions
Publisher: Wiley
Date: 07-09-2013
DOI: 10.1002/ECE3.710
Biodiversity and the Need for Habitat Renewal
Publisher: Wiley
Date: 08-1995
DOI: 10.2307/1941968
Multi-Decadal Changes in Tundra Environments and Ecosystems: Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)
Publisher: Springer Science and Business Media LLC
Date: 24-08-2011
Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island, Yukon Territory, Canada
Publisher: Springer Science and Business Media LLC
Date: 24-08-2011
Evidence of Recent Treeline Dynamics in Southwest Yukon from Aerial Photographs
Publisher: The Arctic Institute of North America
Date: 09-12-2009
DOI: 10.14430/ARCTIC198
The influence of predation risk on foraging behaviour of brushtail possums in Australian woodlands
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/WR03098
Abstract: The potential effects of predation risk on common brushtail possums were investigated in south-eastern Australian woodlands. Patterns of habitat use, foraging costs using giving-up density (GUD) experiments, and indices of body condition and reproductive success were examined at eight sites in two habitat types (eucalypt- or cypress-pine–dominated stands), within three areas of different red fox abundance (high, moderate and low fox density). In cypress-pine–dominated stands, possums travelled further on the ground, visited more feeding stations and had lower GUDs at feeders where foxes were removed than did possums in high-fox-density sites. In contrast, there was no effect of fox removal on the behaviour of possums in eucalypt-dominated stands. Fox removal also had no effect on indices of body condition and reproduction. Minor effects of microhabitat were detected with trackplot and GUD experiments, but, overall, the results suggest that habitat at the stand-level was more important. The non-lethal effects of foxes in different habitats may need to be taken into account when developing conservation strategies for native marsupials.
Circumpolar stakeholder perspectives on Geographic Information Systems for communicating the health impacts of development
Publisher: Elsevier BV
Date: 12-2015
Effects of the Timing of Multiple Grazings by Geese on Net Above-Ground Primary Production of Swards of Puccinellia Phryganodes
Publisher: JSTOR
Date: 09-1991
DOI: 10.2307/2260663
HERBIVORY MEDIATES GRASS–ENDOPHYTE RELATIONSHIPS
Publisher: Wiley
Date: 11-2007
DOI: 10.1890/06-1958.1
Abstract: Endophytic fungi are plant symbionts living asymptomatically within plant tissues. Neotyphodium spp., which are asexual vertically transmitted systemic fungal endophytes of cool-season grasses, are predicted to be plant mutualists. These endophytes increase host plant resistance to environmental stresses and/or increase the production of alkaloid-based herbivore deterrents. The ubiquity of this defense mutualism is unclear, and a variety of alternative mechanisms may explain the observed variation in infection rates, levels of deterrence, and the maintenance of asexual endophytes in grass populations. We found that grass-endophyte interactions are variable and ordered along an herbivory gradient in an undisturbed subarctic alpine ecosystem. Native grass populations in grazed sites had significantly greater frequency of Neotyphodium infection compared to ungrazed sites. Tillers from grazed sites had significantly higher hyphal densities compared to ungrazed sites. The ability of grass-Neotyphodium constituents to deter vertebrate herbivory in natural systems is thought to be rare. In grazed meadows, we showed that endophyte infection resulted in the deterrence of grazing by native vertebrate herbivores. However, the same herbivores did not distinguish between infected and uninfected grass harvested from ungrazed areas. These results demonstrate that the relationship between vertically transmitted endophytes and grasses in the alpine tundra vary greatly within populations. This may be based in part on defense mutualism and is consistent, under varying levels of herbivory, with the predictions of optimal defense theory.
Estimating single nucleotide polymorphism associations using pedigree data: applications to breast cancer
Publisher: Springer Science and Business Media LLC
Date: 06-2013
DOI: 10.1038/BJC.2013.277
Do Exotic Vertebrates Structure the Biota of Australia? An Experimental Test in New South Wales
Publisher: Springer Science and Business Media LLC
Date: 09-2006
Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
Publisher: Wiley
Date: 14-05-2007
DOI: 10.1111/J.1461-0248.2007.01051.X
Abstract: Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
Fifty Years of Science at the Kluane Lake Research Station
Publisher: The Arctic Institute of North America
Date: 07-07-2014
DOI: 10.14430/ARCTIC4398
Does risk of predation influence population dynamics? Evidence from cyclic decline of snowshoe hares
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/WR9950115
Abstract: Like most heavily preyed-upon animals, snowshoe hares (Lepus americanus) have to balance conflicting demands of obtaining food at a high rate and avoiding predators. Adopting foraging behaviours to minimise predation risk may also lead to a decline in condition, and hence fecundity. Predictions of three hypotheses (condition constraint hypothesis, predator-avoidance constraint hypothesis, predation-sensitive foraging (PSF) hypothesis) were tested by comparing changes in the survival and condition of snowshoe hares on four experimental areas in winter during a cyclic peak and decline (1989–1993) near Kluane Lake, Yukon, Canada, where (i) predation risk was reduced by excluding terrestrial predators (FENCE), (ii) food supply was supplemented with rabbit chow ad libitum (FOOD), (iii) these two treatments were combined (FENCE+FOOD), and (iv) an unmanipulated CONTROL was used. Different pattems of survival and changes in body mass were observed in the presence and absence of terrestrial predators. On the CONTROL area, female body mass and fecundity declined, even though sufficient winter forage was apparently available in all years. A similar decrease in body mass was observed on the FOOD treatment, but only during the third year of the population decline. In contrast, female body mass remained high throughout the decline in the absence of terrestrial predators in the FENCE+FOOD and FENCE treatments. Winter survival declined on CONTROL and FENCE areas during the first year of the population decline (1991), but remained higher on FOOD until 1992 and FENCE+FOOD until 1993. These results generally supported the PSF hypothesis where terrestrial predators were present (CONTROL and FOOD grids). Where terrestrial predators were absent (FENCE and FENCE+FOOD), the results supported the alternative condition constraint hypothesis. The evidence suggests that a cascade of sublethal behavioural and physiological effects associated with increased predation risk contribute to the population decline and delayed recovery of cyclic low-phase populations of snowshoe hares.
Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time
Publisher: Wiley
Date: 05-12-2011
DOI: 10.1111/J.1461-0248.2011.01716.X
Abstract: Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future bio ersity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.
The Natural History of Canadian Mammals. By Donna Naughton; color art by, Paul Geraghty, Julius Csotonyi, and Brenda Carter; line art by, Donna Naughton, Micheline Beaulieu-Bouchard, and Alan M
Publisher: University of Chicago Press
Date: 06-2014
DOI: 10.1086/676097
The accuracy of satellite-derived albedo for northern alpine and glaciated land covers
Publisher: Elsevier BV
Date: 09-2016
Plant functional trait change across a warming tundra biome
Publisher: Springer Science and Business Media LLC
Date: 26-09-2018
DOI: 10.1038/S41586-018-0563-7
Abstract: The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
Good neighbours? Determinants of aggregation and segregation among alpine herbivores
Publisher: Informa UK Limited
Date: 09-2013
DOI: 10.2980/20-3-3595
What are the effects of herbivore diversity on tundra ecosystems? A systematic review protocol
Publisher: Springer Science and Business Media LLC
Date: 31-01-2022
DOI: 10.1186/S13750-022-00257-Z
Abstract: Changes in the ersity of herbivore communities can strongly influence the functioning of northern ecosystems. Different herbivores have different impacts on ecosystems because of differences in their diets, behaviour and energy requirements. The combined effects of different herbivores can in some cases compensate each other but lead to stronger directional changes elsewhere. However, the ersity of herbivore assemblages has until recently been a largely overlooked dimension of plant–herbivore interactions. Given the ongoing environmental changes in tundra ecosystems, with increased influx of boreal species and changes in the distribution and abundance of arctic herbivores, a better understanding of the consequences of changes in the ersity of herbivore assemblages is needed. This protocol presents the methodology that will be used in a systematic review on the effects of herbivore ersity on different processes, functions and properties of tundra ecosystems. This systematic review builds on an earlier systematic map on herbivory studies in the Arctic that identified a relatively large number of studies assessing the effects of multiple herbivores. The systematic review will include primary field studies retrieved from databases, search engines and specialist websites, that compare responses of tundra ecosystems to different levels of herbivore ersity, including both vertebrate and invertebrate herbivores. We will use species richness of herbivores or the richness of functional groups of herbivores as a measure of the ersity of the herbivore assemblages. Studies will be screened in three stages: title, abstract and full text, and inclusion will follow clearly identified eligibility criteria, based on their target population, exposure, comparator and study design. The review will cover terrestrial Arctic ecosystems including the forest-tundra ecotone. Potential outcomes will include multiple processes, functions and properties of tundra ecosystems related to primary productivity, nutrient cycling, accumulation and dynamics of nutrient pools, as well as the impacts of herbivores on other organisms. Studies will be critically appraised for validity, and where studies report similar outcomes, meta-analysis will be performed.
Arctic ground squirrelsUrocitellus parryiias drivers and indicators of change in northern ecosystems
Publisher: Wiley
Date: 09-11-2012
Comparison of discriminant function and classification tree analyses for age classification of marmots
Publisher: Wiley
Date: 14-05-2004
Four Decades of Plant Community Change in the Alpine Tundra of Southwest Yukon, Canada
Publisher: Springer Science and Business Media LLC
Date: 24-08-2011
Being high is better: effects of elevation and habitat on arctic ground squirrel demography
Publisher: Wiley
Date: 21-12-2004
What determines disturbance‐productivity‐diversity relationships? The effect of scale, species and environment on richness patterns in an Australian woodland
Publisher: Wiley
Date: 25-06-2003
Climate and nutrient influences on the growth of white spruce trees in the boreal forests of the Yukon
Publisher: Inter-Research Science Center
Date: 30-04-2008
DOI: 10.3354/CR00736
The influence of nesting habitat on reproductive success of the lesser snow goose
Publisher: Canadian Science Publishing
Date: 07-1988
DOI: 10.1139/Z88-245
Abstract: The quality of nesting habitat and the influence of vegetation height on reproductive success of the lesser snow goose (Chen caerulescens caerulescens) were examined. In 1984, geese nesting in tall willow bushes (Salix ssp.) were more successful than in iduals nesting in shorter willows, or in areas with no willows at all. In particular, in iduals nesting in tall willows lost fewer eggs to depredation or abandonment, resulting in a greater number of goslings leaving the nest after hatch. The effect of willow height on reproductive success was independent of female age and relative nest initiation date, both of which are known to affect reproductive success. The degree of the habitat effect was not as great in 1986, but the geese nesting in willow bushes did tend to have greater reproductive success. Since spring environmental conditions influence both the availability and quality of nest sites, the potential importance of the effect of nesting habitat on reproductive success probably varies among years.
Survival, growth, and escape from herbivory are determined by habitat and herbivore species for three Australian woodland plants
Publisher: Springer Science and Business Media LLC
Date: 2004
DOI: 10.1007/S00442-003-1420-3
Abstract: To understand how plant communities are structured by herbivory it is essential to investigate the roles of different herbivores and the responses of a variety of plant species in different habitats. We examined the effects of mammalian herbivores on survival and growth of transplanted seedlings of two native trees (Eucalyptus albensand Callitris glaucophylla), and one native grass (Themeda australis) in white box ( E. albens) woodlands in eastern Australia over 3 years. Herbivores were manipulated using four fencing treatments that successively excluded livestock, macropods, and rabbits from woodland and grassland (cleared pasture). Survival was highest in the absence of mammalian herbivores and in woodlands, and patterns differed among plant species. Survival of T. australis was low, especially in grasslands, and mortality by overgrowth was common in ungrazed treatments. All plant species were taller in fenced plots, and differences between treatments were greater in grassland. Rabbits and livestock had the greatest influence on C. glaucophylla, while T. australis and E. albens were most affected by livestock and macropods. We used field data to parameterize stage-classified matrix models to predict escape from herbivory (escape height >100 cm) for tree species. Reduced herbivory increased the proportion of in iduals reaching escape height after 15 years. Rate of escape was greater in grassland, and this faster growth appeared to counteract much of the negative impact of herbivores. While T. australis was unable to escape herbivory, larger, ungrazed in iduals were more likely to flower and therefore contribute to the maintenance of the population. Our results show that habitat and herbivore species strongly influence the effect of herbivory on vegetation.
Wolf Reproduction in Response to Caribou Migration and Industrial Development on the Central Barrens of Mainland Canada
Publisher: The Arctic Institute of North America
Date: 26-08-2009
DOI: 10.14430/ARCTIC18
Long Foraging Movement of a Denning Tundra Wolf
Publisher: The Arctic Institute of North America
Date: 2004
DOI: 10.14430/ARCTIC495
Foraging by Geese, Isostatic Uplift and Asymmetry in the Development of Salt-Marsh Plant Communities
Publisher: JSTOR
Date: 09-1992
DOI: 10.2307/2260685
Polar Research Education, Outreach and Communication during the fourth IPY: How the 2007–2008 International Polar Year has contributed to the future of education, outreach and communication
Publisher: Unpublished
Date: 2011
Fertilisers mediate the short-term effects of sheep grazing in the Icelandic highlands
Publisher: Agricultural University of Iceland
Date: 2019
DOI: 10.16886/IAS.2019.07
Prevalence and predictability of handling effects in field studies: results from field experiments and a meta‐analysis
Publisher: Wiley
Date: 02-2003
DOI: 10.3732/AJB.90.2.270
Abstract: Various effects on plant growth associated with handling or touching plants are well documented from greenhouse and laboratory studies, but are generally unknown or ignored under field conditions. We examined the prevalence of the effects of handling, at levels typical of many ecological experiments, on aboveground biomass and damage by invertebrate herbivores for a total of 16 common species from three plant communities in western Canada. Significant effects of handling were observed in the alpine meadow and grassland, but not in the boreal forest. Handling reduced aboveground biomass and increased the mean intensity of invertebrate leaf damage for most species. A meta-analysis of the relationship between plant traits and response to handling indicated that woody plants and species without strong chemical or conspicuous morphological defenses were most strongly affected. Overall, our results indicate that potentially confounding effects of routinely s ling plants in the field are widespread and merit further investigation.
Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities
Publisher: IOP Publishing
Date: 12-2011
DOI: 10.1088/1748-9326/6/4/045509
Abstract: Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ecosystems, and (4) address potential lines of investigation for future research. Satellite observations from around the circumpolar Arctic, showing increased productivity, measured as changes in ‘greenness’, have coincided with a general rise in high-latitude air temperatures and have been partly attributed to increases in shrub cover. Studies indicate that warming temperatures, changes in snow cover, altered disturbance regimes as a result of permafrost thaw, tundra fires, and anthropogenic activities or changes in herbivory intensity are all contributing to observed changes in shrub abundance. A large-scale increase in shrub cover will change the structure of tundra ecosystems and alter energy fluxes, regional climate, soil–atmosphere exchange of water, carbon and nutrients, and ecological interactions between species. In order to project future rates of shrub expansion and understand the feedbacks to ecosystem and climate processes, future research should investigate the species or trait-specific responses of shrubs to climate change including: (1) the temperature sensitivity of shrub growth, (2) factors controlling the recruitment of new in iduals, and (3) the relative influence of the positive and negative feedbacks involved in shrub expansion.
Gene flow and the restoration of genetic diversity in a fluctuating collared pika (Ochotona collaris) population
Publisher: Springer Science and Business Media LLC
Date: 09-2013
“These Trees Have Stories to Tell”: Linking Dënesǫ́łıné Oral History of Caribou Use with Trample Scar Frequency on Black Spruce Roots at Ɂedacho Kué
Publisher: The Arctic Institute of North America
Date: 05-10-2021
DOI: 10.14430/ARCTIC73160
Abstract: For thousands of years Ɂedacho Kué (Artillery Lake, Northwest Territories) has been a key water crossing site for barren-ground caribou (Rangifer tarandus groenlandicus). Human disturbance of barren-ground caribou habitat in northern Canada has emerged as an important focus of study in the last decade particularly in the Bathurst range of the Northwest Territories where caribou populations have declined by more than 95% since the 1980s. Guided by local Indigenous leaders and Elders, a collaborative research project was developed with the Dënesǫ́łıné people of Łutsël K’e Dëne First Nation (2012 – 14). This paper describes linkages between knowledge derived from Dënesǫ́łıné oral history and quantitative dendroecological analysis of tr le scars on black spruce (Picea mariana) root s les collected at Ɂedacho Kué to provide a better understanding of caribou use at this location. Findings from oral histories and dendroecology analysis were consistent with one another and with previous dendroecology study in the region, although some discrepancies were detected in data from 1995 – 2006 that require further study to elucidate. Key findings include relatively low caribou use at Ɂedacho Kué during the 1930s and late 1960s, with use increasing into the 1970s and peaking in the late 1980s, as well as Elder and hunter reports of no caribou in some years between 2005 and 2012. This work addresses a gap in scientific data about barren-ground caribou movements at Ɂedacho Kué prior to satellite collar use in 1996 and corroborates previously documented oral histories about the enduring value of Ɂedacho Kué as critical habitat to barren-ground caribou. Given the drastic decline of the Bathurst caribou over the last two decades, more research is needed to understand movements and their relationship to population dynamics. In this context, the research approach described in this paper could be used as an ex le of how to meaningfully bring together place-based Indigenous knowledge and science in addressing an urgent issue of Arctic sustainability.
Ecological Dynamics Across the Arctic Associated with Recent Climate Change
Publisher: American Association for the Advancement of Science (AAAS)
Date: 11-09-2009
Abstract: The Arctic is experiencing some of the most rapid climate change currently under way across the globe, but consequent ecological responses have not been widely reported. At the close of the Fourth International Polar Year, Post et al. (p. 1355 ) review observations on ecological impacts in this sensitive region. The widespread changes occurring in terrestrial, freshwater, and marine systems, presage changes at lower latitudes that will affect natural resources, food production, and future climate buffering.
Eavesdropping on the Neighbourhood: Collared Pika (Ochotona collaris) Responses to Playback Calls of Conspecifics and Heterospecifics
Publisher: Wiley
Date: 09-2009
Influence of food hoarding behavior on the over-winter survival of pikas in strongly seasonal environments
Publisher: Springer Science and Business Media LLC
Date: 06-11-2008
DOI: 10.1007/S00442-008-1197-5
Abstract: Food hoarding is a behavioral adaptation of some herbivores to manage food availability through time and space. In strongly seasonal environments, where summer growing seasons are short relative to winter, an earlier start to hoarding should increase the amount of vegetation stored for winter and improve subsequent survival. We examined hoarding behavior ('haying') and its impact on survival for a small alpine lagomorph, the collared pika (Ochotona collaris) in Yukon, Canada. We used a combination of video surveillance, haypile measurements, and survival data from marked in iduals of known age and sex. Annual haypile initiation was strongly influenced by age and year. Adult pikas began haying an average of 16 days earlier in 2004 relative to 2005, whereas young of the year (juveniles) did not vary in the timing of haypile initiation. The mean haying rate per hour increased monthly from 3.7 +/- 0.7 trips in June to 6.6 +/- 0.8 trips in August. Simulation analysis estimated the median haypile mass (dry weight) by mid-September to be 5.5 kg. At least 75% of simulated haypiles had a minimum of 90 days (3 months) of food reserves, and 50% of simulated haypiles had a minimum of 177 days (5.9 months) of food reserves by mid-September, supporting the hypothesis that haypiles serve as the primary source of food during winter. Survival was greatest for pikas in 2005 when they began haying prior to 31 July, but the benefits of earlier accumulation of vegetation on survival also varied between years. The implications of earlier spring snowmelt are discussed with respect to pika foraging and overwinter survival.
SPATIAL HETEROGENEITY, NOT VISITATION BIAS, DOMINATES VARIATION IN HERBIVORY: COMMENT
Publisher: Wiley
Date: 10-2004
DOI: 10.1890/03-3169
The role of lesser snow geese as nitrogen processors in a sub-arctic salt marsh
Publisher: Springer Science and Business Media LLC
Date: 04-1989
DOI: 10.1007/BF00378235
Hiding in the background: community-level patterns in invertebrate herbivory across the tundra biome
Publisher: Springer Science and Business Media LLC
Date: 03-09-2019
Influences of chronic and current season grazing by collared pikas on above-ground biomass and species richness in subarctic alpine meadows
Publisher: Springer Science and Business Media LLC
Date: 16-06-2005
DOI: 10.1007/S00442-005-0127-Z
Abstract: We studied an alpine herbivory gradient established by collared pikas, a small central place foraging lagomorph, to examine the effects of multiple grazing levels on above-ground live biomass (AGB) and species richness (SR) in alpine tundra. The effects of within-season (four s ling periods), multi-season (across three summers) and longer-term dynamics (inferred from spatial location of vegetation with respect to pika haypiles) were examined. Along the grazing gradient, we found support for and against hypotheses that propose biphasic, increasing, or decreasing responses to herbivory, both in terms of AGB and SR. Our results suggest that plant-herbivore predictability is still weak. To further examine the impact of herbivory, we experimentally removed pikas using mesh exclosures placed at increasing distance from the edge of talus occupied by pikas. AGB after the second consecutive year of herbivore exclusion increased by 125% compared to control plots in highly grazed areas adjacent to talus ( 6 m from talus. AGB was highest in meadow patches previously grazed by pikas compared to those with little grazing history, but this response was only observed after two seasons following release from herbivory. Grazed sites at distances of 1-6 m had the highest SR. These results indicate that multi-year measurements of growth are particularly relevant in ecosystems dominated by long-lived perennials in regions where productivity is low. Infrequent herbivore vacancies may provide local short-term release from pika grazing, thereby contributing to the persistence of productive, highly palatable vegetation.
Diet breadth ofGynaephora groenlandica(Lepidoptera: Erebidae): is polyphagy greater in alpine versus Arctic populations?
Publisher: Cambridge University Press (CUP)
Date: 29-05-2014
DOI: 10.4039/TCE.2014.35
Abstract: Gynaephora groenlandica (Wocke) (Lepidoptera: Erebidae) is a cold-adapted species, whose life history traits are dictated by cold and short Arctic summers. We used a recently discovered alpine tundra population in southwestern Yukon, Canada to investigate local adaptations to habitats with different environmental conditions (alpine versus Arctic). Using cafeteria-type experiments and field observations we examined the diet breadth of alpine populations of G. groenlandica beringiana Schmidt and Cannings, and compared these to published data on High Arctic populations of G. groenlandica groenlandica and to the closely related G. rossii Curtis. Gynaephora groenlandica beringiana appears to have a broader diet than High Arctic populations, but similar to that exhibited by alpine populations of G. rossii . Such trends could emerge from reduced synchrony between herbivores and their host plants in less extreme environments, and possibly from a reduced incidence of parasitoids in the life cycle of these populations. Our findings indicate the larval host plant plasticity of G. groenlandica in different environments, and are relevant to predictions regarding the fate of these populations under climate warming scenarios.
Evidence for Selective Caching by Arctic Ground Squirrels Living in Alpine Meadows in the Yukon
Publisher: The Arctic Institute of North America
Date: 29-01-2010
DOI: 10.14430/ARCTIC449
Isolation and characterization of microsatellite loci for the collared pika (Ochotona collaris) and their cross‐amplification in five other Ochotona species
Publisher: Wiley
Date: 20-04-2009
DOI: 10.1111/J.1755-0998.2008.02397.X
Abstract: We developed primers for eight polymorphic microsatellite loci isolated from the collared pika, Ochotona collaris, and also tested nine loci previously developed for the American pika, O. princeps, for use in O. collaris. Forty-six in iduals from an O. collaris population in the southern Yukon were genotyped using all 17 loci. The average number of alleles per locus was six and the average observed heterozygosity was 0.59. All loci were tested for use in four Asian pika species and all but two loci lified reliably in these species.
Spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis) at the northern limit of their native range
Publisher: Canadian Science Publishing
Date: 05-2020
Abstract: The Canadian Rocky Mountains are one of the few places on Earth where the spatial genetic structure of wide-ranging species has been relatively unaffected by anthropogenic disturbance. We characterized the spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis Shaw, 1804) in the northern portion of their range. Using microsatellites from 1495 in iduals and mitochondrial DNA sequences from 188 in iduals, we examined both broad- and fine-scale spatial genetic structure, assessed sex-biased gene flow within the northern portion of the species range, and identified geographic patterns of genetic ersity. We found that broad-scale spatial genetic structure was consistent with barriers to movement created by major river valleys. The fine-scale spatial genetic structure was characterized by a strong isolation-by-distance pattern, and analysis of neighborhood size using spatial autocorrelation indicated gene flow frequently occurred over distances of up to 100 km. However, analysis of sex-specific spatial autocorrelation and analysis of mitochondrial haplotype distributions failed to detect any evidence of sex-biased gene flow. Finally, our analyses reveal decreasing genetic ersity with increasing latitude, consistent with patterns of post-glacial recolonization of the Rocky Mountains.
Herbivory Network: An international, collaborative effort to study herbivory in Arctic and alpine ecosystems
Publisher: Elsevier BV
Date: 09-2016
Variation in pika (Ochotona collaris, O. princeps) vocalizations within and between populations
Publisher: Wiley
Date: 02-06-2009
Global maps of soil temperature.
Publisher: Wiley
Date: 11-02-2022
DOI: 10.1111/GCB.16060
Abstract: Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km
Influence of habitat quality, patch size and connectivity on colonization and extinction dynamics of collared pikas Ochotona collaris
Publisher: Wiley
Date: 18-08-2004
Polygynandry and even-sexed dispersal in a population of collared pikas, Ochotona collaris
Publisher: Elsevier BV
Date: 04-2012
Understanding Earth's Polar Challenges: International Polar Year 2007–08, Summary by the IPY Joint Committee, edited by I. Krupnik, I. Allison, R. Bell, P. Cutler, D. Hik, J. López-Martinez, V. Rachol
Publisher: The Arctic Institute of North America
Date: 23-02-2015
DOI: 10.14430/ARCTIC4466
Responses of white spruce (Picea glauca) to experimental warming at a subarctic alpine treeline
Publisher: Wiley
Date: 06-12-2006
Grazing history versus current grazing: leaf demography and compensatory growth of three alpine plants in response to a native herbivore (Ochotona collaris)
Publisher: Wiley
Date: 04-2002
Phenology and species determine growing‐season albedo increase at the altitudinal limit of shrub growth in the sub‐Arctic
Publisher: Wiley
Date: 09-05-2016
DOI: 10.1111/GCB.13297
Abstract: Arctic warming is resulting in reduced snow cover and increased shrub growth, both of which have been associated with altered land surface-atmospheric feedback processes involving sensible heat flux, ground heat flux and biogeochemical cycling. Using field measurements, we show that two common Arctic shrub species (Betula glandulosa and Salix pulchra), which are largely responsible for shrub encroachment in tundra, differed markedly in albedo and that albedo of both species increased as growing season progressed when measured at their altitudinal limit. A moveable apparatus was used to repeatedly measure albedo at six precise spots during the summer of 2012, and res led in 2013. Contrary to the generally accepted view of shrub-covered areas having low albedo in tundra, full-canopy prostrate B. glandulosa had almost the highest albedo of all surfaces measured during the peak of the growing season. The higher midsummer albedo is also evident in localized MODIS albedo aggregated from 2000 to 2013, which displays a similar increase in growing-season albedo. Using our field measurements, we show the ensemble summer increase in tundra albedo counteracts the generalized effect of earlier spring snow melt on surface energy balance by approximately 40%. This summer increase in albedo, when viewed in absolute values, is as large as the difference between the forest and tundra transition. These results indicate that near future (<50 years) changes in growing-season albedo related to Arctic vegetation change are unlikely to be particularly large and might constitute a negative feedback to climate warming in certain circumstances. Future efforts to calculate energy budgets and a sensible heating feedback in the Arctic will require more detailed information about the relative abundance of different ground cover types, particularly shrub species and their respective growth forms and phenology.
Introduction: Biology of the Canadian Arctic: A Crucible for Change in the 21st Century
Publisher: Oxford University Press (OUP)
Date: 04-2004
DOI: 10.1093/ICB/44.2.81
Climate warming as a driver of tundra shrubline advance
Publisher: Wiley
Date: 25-09-2017
Does seasonal variation in forage quality influence the potential for resource competition between muskoxen and Peary caribou on Banks Island?
Publisher: UiT The Arctic University of Norway
Date: 03-2002
DOI: 10.7557/2.22.2.1533
Abstract: Inter- and intra-annual variation in forage quality may influence population dynamics of Peary caribou and muskoxen on Banks Island. From 1993 to 1998 we collected 300 composite s les of sedge (Carex aquatilis and Carex spp.), willow (Salix arctica), legume (Oxytropis spp. and Astragalus spp.), and avens (Dryas integrifolia). S les were collected in mid-June (start of the growing season), mid-July (peak of the growing season), mid-late August (senescence), and early (November), mid- (February), and late- (April/May) winter. We analysed forages for percent digestibility (in vitro acid-pepsin dry matter digestibility), crude protein (CP), fibre, lignin, and energy content. There was significant inter-annual variation in levels of lignin, fibre, and energy, and significant intra-annual (seasonal) variation for all quality measures and forages, which reflected the strong difference in quality between summer and winter. We discuss the relationship between forage quality and seasonal diet composition of Peary caribou and muskoxen, and the potential implications for the reduced Peary caribou and high muskoxen populations.
Giving-up densities and foraging behaviour indicate possible effects of shrub encroachment on arctic ground squirrels
Publisher: Elsevier BV
Date: 09-2014
CH4 uptake along a successional gradient in temperate alpine soils
Publisher: Springer Science and Business Media LLC
Date: 2020
Respecting and Aligning Knowledge Systems in Northern Canada: Beyond the International Polar Year
Publisher: Edward Elgar Publishing
Date: 30-03-2012
Moss Mediates the Influence of Shrub Species on Soil Properties and Processes in Alpine Tundra
Publisher: Public Library of Science (PLoS)
Date: 19-10-2016
Automated content analysis as a tool for research and practice: a case illustration from the Prairie Creek and Nico environmental assessments in the Northwest Territories, Canada
Publisher: Informa UK Limited
Date: 31-10-2017
HERBIVORY MEDIATES GRASS–ENDOPHYTE RELATIONSHIPS: REPLY
Publisher: Wiley
Date: 12-2008
DOI: 10.1890/08-1103.1
Increases in the Net Above-Ground Primary Production of a Salt-Marsh Forage Grass: A Test of the Predictions of the Herbivore-Optimization Model
Publisher: JSTOR
Date: 03-1990
DOI: 10.2307/2261044
Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass?
Publisher: Wiley
Date: 12-2001
The effects of different management interventions on degraded rangelands in Iceland
Publisher: Wiley
Date: 15-08-2021
DOI: 10.1002/LDR.4057
Abstract: Loss of vegetation and soil erosion are symptoms of widespread rangeland degradation across most of the Icelandic highlands. Areas at different stages of degradation coexist as a mosaic that includes both vegetated heathlands, and exposed gravelly deserts. Revegetation efforts have included fertilizer applications and grazing exclusion to increase plant biomass and reduce bare ground, but their effectiveness is predicted to differ depending on the stage of degradation for a certain area. In this study, we used a 4‐year field experiment to test the predictions of a state‐and‐transition model for the Icelandic highlands. We measured the combined effects of grazing exclusion and factorial applications of nitrogen (N), phosphorus (P), and potassium (K) fertilizers, on plant biomass, species richness, amount of exposed bare ground and plant community composition in a dwarf‐shrub heathland and a gravelly desert habitat. After 4 years: (1) grazing exclusion alone had no effect in either habitat (2) fertilizers increased biomass in both habitats, especially in plots treated with NP or NK (3) the combination of fertilizers and grazing exclusion produced the greatest amount of aboveground biomass, predominantly of forb and graminoid species. In the dwarf‐shrub heath, the increase in biomass in fertilized and fenced plots also corresponded to a loss in species richness, whereas in the gravelly desert, increased biomass reduced the amount of bare ground without reducing species richness. Our results reinforce the importance in understanding the effects of different management interventions across ecological conditions to determine the most effective revegetation approach.
Mountain‐top and valley‐bottom experiences: the stress axis as an integrator of environmental variability in arctic ground squirrel populations
Publisher: Wiley
Date: 07-02-2012
Demographic analysis of a declining pika Ochotona collaris population: linking survival to broad‐scale climate patterns via spring snowmelt patterns
Publisher: Wiley
Date: 19-07-2007
DOI: 10.1111/J.1365-2656.2007.01276.X
Abstract: 1. Demographic analysis is essential in order to determine which factors, such as survival, fertility and other life-history characteristics, have the greatest influence on a population's rate of growth (lambda). 2. We used life-table response experiments (LTREs) to assess the relative importance of survival and fertility rates for an alpine lagomorph, the collared pika Ochotona collaris, using 12 years (1995-2006) of census data. The LTRE analysis was repeated for each of three subpopulations within the main study site that were defined by aspect (east, west and south). 3. Across the entire study site, the survival and fertility of adults contributed 35.6 and 43.5%, respectively, to the variance observed in the projected population growth rate, V(lambda), whereas juvenile survival contributed 20.9%. Adult survival and fertility contributed approximately equal amounts for each subpopulation when considered separately, although their rank order varied spatially. 4. Adult survival across the entire site was positively correlated to the Pacific Decadal Oscillation (PDO) with a time lag of 1 year, and was uncorrelated to adult density. The PDO was negatively correlated to the timing of spring snowmelt at our site, implicating the importance of earlier spring conditions and plant phenology on the subsequent winter survival of adults and therefore, population growth. 5. When subpopulations were analysed separately, survivals and fertilities were variously correlated to lagged PDO and adult densities, but the patterns varied spatially. Therefore, the mechanisms underlying V(lambda) can vary substantially over relatively short distances.
Landscape ecology of the burrowing bettong: fire and marsupial biocontrol of shrubs in semi-arid Australia
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/RJ06041
Abstract: Prior to European settlement, medium-sized marsupials, especially bettongs (Bettongia spp.), were widely distributed across arid and semi-arid Australia. Most disappeared rapidly in the late 1800s in the earliest settled rangelands such as the West Darling region of western New South Wales following the spread of domestic herbivores, rabbit invasion, exotic predators and loss of habitat. Because the burrowing bettong (Bettongia lesueur) is the only fossorial macropod species, it left a clearly visible record of its past presence, distribution and habitat preferences in the form of substantial relict warrens, particularly in stony, ‘hard-red’ habitats. With the reduction in fire frequency because of excessive grazing pressures following European settlement in the 19th century, there was a rapid increase in the density of unpalatable native shrubs. We examine the hypothesis that periodic wildfires and browsing by bettongs were together able to regulate shrub densities in semi-arid rangelands in Australia. Information from various sources concerning the effects of fire, rainfall and browsing on the demography of shrubs was used to construct a model of shrub population dynamics. The model indicates the potential for two states for a given bettong density: first, a low shrub density maintained by a combination of periodic fire and bettong browsing and second, a high shrub density in the absence of fire. These results have broad implications for pastoral and conservation management in Australian semi-arid rangelands.
Extending the stress‐gradient hypothesis – is competition among animals less common in harsh environments?
Publisher: Wiley
Date: 18-12-2012
Response of Wolves to Experimental Disturbance at Homesites
Publisher: Wiley
Date: 04-2007
DOI: 10.2193/2005-744
Spring and summer monthly MODIS LST is inherently biased compared to air temperature in snow covered sub-Arctic mountains
Publisher: Elsevier BV
Date: 02-2017
First Records of the Arctic Moth <i>Gynaephora groenlandica</i> (Wocke) South of the Arctic Circle: A New Alpine Subspecies
Publisher: The Arctic Institute of North America
Date: 22-11-2013
DOI: 10.14430/ARCTIC4329
Influence of shrub canopies on growth rate and pre‐hibernation mass of juvenile arctic ground squirrels
Publisher: Wiley
Date: 08-2014
DOI: 10.2981/WLB.00038
Abstract: The wide‐spread encroachment of canopy‐forming shrubs into northern and alpine tundra communities is likely to alter many plant—animal interactions, with direct and indirect impacts on herbivore populations. Specifically, shrub encroachment may impact habitat quality for herbivores by changing predation risk as a result of reduced visibility. We investigated the association between visibility and growth of juvenile arctic ground squirrels Urocitellus parryii across an alpine tundra ecotone with varying shrub cover. Marked in iduals were weighed throughout the period following emergence from natal burrows in early summer until just prior to hibernation. Both males and females showed a positive association between habitat‐specific visibility and post‐emergence growth rate. There was a positive relationship between post‐emergence juvenile growth rate and pre‐hibernation mass for females but not males. As shrubs increase, ground squirrel populations may be adversely affected by reductions in habitat‐scale visibility.
Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome
Publisher: Springer Science and Business Media LLC
Date: 19-06-2017
Biotic interactions mediate patterns of herbivore diversity in the Arctic
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1111/GEB.12470
Climate sensitivity of shrub growth across the tundra biome
Publisher: Springer Science and Business Media LLC
Date: 06-07-2015
DOI: 10.1038/NCLIMATE2697
Growth responses of arctic graminoids following grazing by captive lesser snow geese
Publisher: Springer Science and Business Media LLC
Date: 04-1993
DOI: 10.1007/BF00328955
Population Changes of the Vertebrate Community during a Snowshoe Hare Cycle in Canada's Boreal Forest
Publisher: JSTOR
Date: 10-1995
DOI: 10.2307/3545676
Discrimination of intra- and inter-specific forage quality by collared pikas (Ochotona collaris)
Publisher: Canadian Science Publishing
Date: 06-2008
DOI: 10.1139/Z08-023
Abstract: The specific nutritional characteristics by which herbivores evaluate their foraging options are complex. We experimentally manipulated the crude protein and water content of two forage species ( Carex consimilis Holm. (= Carex bigelowii Torr. ex Schwein.) and Polygonum bistorta L.) commonly cached by collared pikas ( Ochotona collaris (Nelson, 1893)) to determine their influence on inter- and intra-specific forage selection. Preference data were collected for 27 pikas using cafeteria-style feeding trials in a randomized block design. A three-way interaction (species × protein × water) suggested that pikas made conditional forage selection decisions while caching these plants. The interaction was driven by greater selection for fresh rather than dried C. consimilis when both were not fertilized. Water content had no effect on the selection of either fertilized C. consimilis or fertilized P. bistorta. Overall, our results indicate that pikas made subtle decisions about their selection of vegetation during caching, based on variation in nitrogen and water content in addition to species-specific selection criteria. Further, our results imply that tests of foraging theory may need to consider intra-specific variation in forage characteristics, as well as inter-specific ranking of forage species.
A methane sink in the Central American high elevation páramo: Topographic, soil moisture and vegetation effects
Publisher: Elsevier BV
Date: 03-2020
Isolation and characterization of microsatellite markers in hoary marmots (Marmota caligata)
Publisher: Wiley
Date: 25-10-2004
The Lakehead Manifesto: Principles for Research and Development in the North
Publisher: The Arctic Institute of North America
Date: 05-06-2013
DOI: 10.14430/ARCTIC4284
Plant interactions are unimportant in a subarctic–alpine plant community
Publisher: Wiley
Date: 09-2009
DOI: 10.1890/08-0924.1
Abstract: We investigated whether plant interaction intensity in a subarctic–alpine meadow is important for determining community structure and species abundance. Using two common species as phytometers, we measured interaction intensity using a neighbor removal approach. Eight biotic and abiotic variables known to influence species abundance and community structure were measured, with regression trees used to examine how plant interactions and the biotic and abiotic variables were related to species evenness, richness, and phytometer spatial cover. A range of interactions was present, with both strong competition and facilitation present over small‐scale abiotic and biotic gradients. Despite the variation in interaction intensity, it was generally unrelated to either community structure or phytometer cover. In other words, plant interactions were intense in many cases but were not important to community structure. This may be due to the prevalence of clonal species in this system and the influence of previous year's interactions on plant survival and patterns of community structure. These results also suggest how conflicting theories of the role of competition in unproductive environments may be resolved. Our findings suggest that plant interactions may be intense in reducing in idual growth, while simultaneously not important in the context of community structure. Plant interactions need to be viewed and tested relative to other factors and stresses to accurately evaluate their importance in plant communities, with continued differentiation between the intensity of plant interactions and their relative importance in communities.
Science and the St Elias: an evolving framework for sustainability in North America's highest mountains
Publisher: Wiley
Date: 22-08-2003
Plant Chemical Defense and Twig Selection by Snowshoe Hare: An Optimal Foraging Perspective
Publisher: JSTOR
Date: 11-1992
DOI: 10.2307/3545021
Need for mountain weather stations climbs
Publisher: American Association for the Advancement of Science (AAAS)
Date: 29-11-2019
Effects of Leaf Size on Forage Selection by Collared Pikas, Ochotona Collaris
Publisher: Informa UK Limited
Date: 08-2008
After the frass: foraging pikas select patches previously grazed by caterpillars
Publisher: The Royal Society
Date: 23-06-2013
Abstract: Interactions among herbivores can shape the structure of their communities and drive their dynamics. However, detecting herbivore interactions can be challenging when they are deferred in space or time. Moreover, interactions among distantly related groups of herbivores, such as vertebrates and invertebrates, are poorly understood. We investigated the effect of invertebrate herbivory on the subsequent foraging choices of a small alpine-dwelling vertebrate, the collared pika ( Ochotona collaris ). We carried out a field experiment within pika territories, by presenting them with a choice of foraging sites following manipulation of invertebrate (caterpillar) herbivory. Pikas actively selected areas with increased, recent invertebrate herbivory. While the underlying mechanisms behind this interaction remain unknown, our results demonstrate a positive effect of invertebrate herbivores on subsequent vertebrate foraging preferences for the first time. Even among distantly related taxa, such interactions where one herbivore is cueing on the foraging of another, could drive the creation of herbivory hotspots, with cascading consequences for ecosystem processes.
Recent climate-related terrestrial biodiversity research in Canada's Arctic national parks: review, summary, and management implications
Publisher: Informa UK Limited
Date: 09-2012
Herbivory in Arctic Ecosystems
Publisher: Elsevier
Date: 2020
Polar bear (Ursus maritimus) maternity denning habitat in western Hudson Bay: a bottom-up approach to resource selection functions
Publisher: Canadian Science Publishing
Date: 06-2005
DOI: 10.1139/Z05-075
Abstract: We examined habitat characteristics of 101 polar bear (Ursus maritimus Phipps, 1774) den sites and 83 adjacent unoccupied sites in western Hudson Bay, Canada, between mid-August and early October 2001 and 2002. Bears denned almost exclusively in peat banks (n = 100) along the edges of creeks, rivers, and lakes adjacent to open lichen tundra sites. Den sites differed from unoccupied sites by having greater tree cover (P = 0.002), less moss cover (P 0.001), and less herbaceous cover (P = 0.005). The presence of tree roots improved substrate stability, providing support to den structures. Den entrance azimuths were weighted toward a southeasterly aspect (P 0.005), away from the prevailing northwest winds. To identify habitats with the greatest relative probability of having a den, a resource selection function (RSF) model was developed using remote sensing imagery and 1245 known den locations. High normalized difference vegetation index and brightness values derived from Landsat imagery, which were in close proximity to water, corresponded well with polar bear den sites. Identification of critical denning areas through the use of RSF will provide resource managers with a valuable tool for ensuring the protection of denning habitat, and consequently female bears and their young.
Linking foraging behavior to population density: An assessment of GMM models for Dall sheep
Publisher: Elsevier BV
Date: 03-2008
Rapid detection of fungal endophytes in grasses for large‐scale studies
Publisher: Wiley
Date: 07-07-2006
Uniform female‐biased sex ratios in alpine willows
Publisher: Wiley
Date: 07-2012
DOI: 10.3732/AJB.1200107
Abstract: The development of biased sex ratios in dioecious plant species has been ascribed to either (1) factors influencing differential adult mortality of male and female plants or (2) factors acting at an early life stage that determine seed sex ratio or seedling survival. To discriminate between these two competing hypotheses, we surveyed sex and age of 379 in iduals from five species of the genus Salix across 11 alpine valleys in the southwest Yukon. We observed uniformly female-biased sex ratios of approximately 2:1 across all adult age cohorts and patch sizes of the five willow species. No spatial variation in sex ratio occurred that could be associated with site-specific characteristics such as elevation or aspect. Our results indicate that the female-biased sex ratios in the alpine willow species investigated in this study are not a consequence of ecological processes acting on established adult plants. The sex ratio is instead determined at an early life stage by a mechanism that remains unknown.
The sheep in wolf's clothing? R ecognizing threats for land degradation in Iceland using state‐and‐transition models
Publisher: Wiley
Date: 15-05-2018
DOI: 10.1002/LDR.2978
Warming the tundra: reciprocal responses of invertebrate herbivores and plants
Publisher: Wiley
Date: 13-04-2015
DOI: 10.1111/OIK.02190
Predicting Effects of Predation on Conservation of Endangered Prey
Publisher: Wiley
Date: 17-06-1998
The role of phenotypic plasticity in responses of hunted thinhorn sheep ram horn growth to changing climate conditions
Publisher: Wiley
Date: 19-03-2010
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