Yukon Territory Research Articles

“At risk” languages and the road to recovery: a case from the Yukon

ABSTRACT This article traces the various ways that ‘languages at risk’ in the Yukon Territory, Canada, are imagined and managed across a range of ‘stakeholders.’ Predicated on a history of oppression and the management of risk in the U.S. and Canada, aboriginal language endangerment has arisen from insecurities about communicative diversity. Conversely language revitalization has arisen from insecurities about the loss of diversity. As this article demonstrates, ideologies of loss and the insecurities entailed therein resonate differently across different speakers, language activists, and institutions, resulting in different perceptions of loss, different experiences of risk, and different approaches to recovery. Moving from policy and the institutionalization of aboriginal languages to people’s reflections and concerns about their own welfare, this article argues that insecurities about language are ultimately insecurities about other vulnerabilities, including the shifting political-moral terrain of the nation-state and First Nations.

A Comparative Policy Analysis of Wild Food Policies Across Ontario, Northwest Territories, and Yukon Territory, Canada

Access to and availability of food harvested from the land (called traditional food, country food, or wild food) are critical to food security and food sovereignty of Indigenous People. These foods can be particularly difficult to access for those living in urban environments. We ask: what policies are involved in the regulation of traditional/country foods and how do these policies affect access to traditional/country food for Indigenous Peoples living in urban centers? Which policies act as barriers? This paper provides a comparative policy analysis of wild food policies across Ontario, the Northwest Territories (NWT), and the Yukon Territory, Canada, by examining and making comparisons between various pieces of legislation, such as fish and wildlife acts, hunting regulations, food premises legislation, and meat inspection regulations. We provide examples of how some programs serving Indigenous Peoples have managed to provide wild foods, using creative ways to operate within the existing system. While there is overwhelming evidence that traditional/country food plays a critical role for the health and well-being of Indigenous Peoples within Canada, Indigenous food systems are often undermined by provincial and territorial wild food policies. Provinces like Ontario with more restrictive policies may be able to learn from the policies in the Territories. We found that on a system level, there are significant constraints on the accessibility of wild foods in urban spaces because the regulatory food environment is designed to manage a colonial market-based system that devalues Indigenous values of sharing and reciprocity and Indigenous food systems, particularly for traditional/country foods. Dismantling the barriers to traditional/country food access in that system can be an important way forward.

A Pan-Canadian Perspective on Education and Training Priorities for Physiotherapists. Part 1: Foundations for Clinical Practice.

Purpose: Canadian physiotherapists who participated in the Physio Moves Canada (PMC) project of 2017 identified the current state of training programmes as a threat facing professional growth of the discipline in Canada. One purpose of this project was to identify key priority areas for physiotherapist training programmes as identified by academics and clinicians across Canada. Method: The PMC project included a series of interviews and focus groups conducted across clinical sites in every Canadian province and in the Yukon Territory. Data were interpreted using descriptive thematic analysis; identified sub-themes were returned to participants for reflection. Results: Overall, 116 physiotherapists and 1 physiotherapy assistant participated in 10 focus groups and 26 semi-structured interviews. Participants identified critical appraisal of continuing professional development options, knowledge translation, cultural fluency, professionalism, pharmaceutical knowledge, and clinical reasoning as priorities. For clinical practice specifically, participants identified practical knowledge, scope of practice, exercise prescription, health promotion, care of complex patients, and digital technologies as the priorities. Conclusion: Training priorities identified by participants may be useful to physiotherapy educators in preparing graduates to be adaptable and flexible primary health care providers for the future needs of a diverse population.

A Pan-Canadian Perspective on Education and Training Priorities for Physiotherapists. Part 2: Professional Interactions and Context of Practice.

Purpose: Canadian physiotherapists who participated in the Physio Moves Canada (PMC) project of 2017 identified the state of training programmes as a threat facing professional growth of the discipline. One purpose of the project was to identify priority areas for physiotherapist training programmes as identified by academics and clinicians across Canada. Method: The PMC project included a series of interviews and focus groups conducted across clinical sites in every Canadian province and in Yukon Territory. Data were interpreted using descriptive thematic analysis; identified sub-themes were returned to participants for reflection. Results: Overall, 116 physiotherapists and 1 physiotherapy assistant participated in 10 focus groups and 26 semi-structured interviews. Results are presented using the curriculum guidelines of the time for organization. Here we describe two themes: Physiotherapy Professional Interactions, further defined by interpersonal and interprofessional competencies, and Context of Practice further defined by advocacy, leadership, community awareness, and business competencies. Conclusions: Participants appear to express a desire for programmes to train reflexive and adaptable primary health care practitioners with strong foundational knowledge and clinical expertise, complemented by interpersonal and interprofessional skills to empower physiotherapists to effectively care and advocate for patients, to lead health care teams, and to share ideas to inspire change towards a future of physiotherapy practice.

The sensitivity of snow hydrology to changes in air temperature and precipitation in three North American headwater basins

Whether or not the impact of warming on mountain snow and runoff can be offset by precipitation increases has not been well examined, but it is crucially important for future downstream water supply. Using the physically based Cold Regions Hydrological Modelling Platform (CRHM), elasticity (percent change in runoff divided by change in a climate forcing) and the sensitivity of snow regimes to perturbations were investigated in three well-instrumented mountain research basins spanning the northern North American Cordillera. Hourly meteorological observations were perturbed using air temperature and precipitation changes and were then used to force hydrological models for each basin. In all three basins, lower temperature sensitivities of annual runoff volume (≤ 6% °C−1) and higher sensitivities of peak snowpack (−17% °C−1) showed that annual runoff was far less sensitive to temperature than the snow regime. Higher and lower precipitation elasticities of annual runoff (1.5 – 2.1) and peak snowpack (0.7 – 1.1) indicated that the runoff change is primarily attributed to precipitation change and, secondarily, to warming. A low discrepancy between observed and simulated precipitation elasticities showed that the model results are reliable, and one can conduct sensitivity analysis. The air temperature elasticities, however, must be interpreted with care as the projected warmings range beyond the observed temperatures and, hence, it is not possible to test their reliability. Simulations using multiple elevations showed that the timing of peak snowpack was most sensitive to temperature. For the range of warming expected from North American climate model simulations, the impacts of warming on annual runoff, but not on peak snowpack, can be offset by the size of precipitation increases projected for the near-future period 2041–2070. To offset the impact of 2 °C warming on annual runoff, precipitation would need to increase by less than 5% in all three basins. To offset the impact of 2 °C warming on peak snowpack, however, precipitation would need to increase by 12% in Wolf Creek in Yukon Territory, 18% in Marmot Creek in the Canadian Rockies, and an amount greater than the maximum projected at Reynolds Mountain in Idaho. The role of increased precipitation as a compensator for the impact of warming on snowpack is more effective at the highest elevations and higher latitudes. Increased precipitation leads to resilient and strongly coupled snow and runoff regimes, contrasting sharply with the sensitive and weakly coupled regimes at low elevations and in temperate climate zones.

Mitochondrial capture and subsequent genetic divergence generates a novel haplogroup: evidence from ancient and ongoing hybridization in mule and white-tailed deer

AbstractOdocoileus virginianus (white-tailed deer) and O. hemionus (mule deer) are sympatric across much of North America. Molecular evidence suggests that up to 24% of individuals in some populations are a product of hybrid ancestry. Several studies have alluded to ancient and recent introgression between Odocoileus spp.; however, no divergence dates were proposed. Herein, phylogenetic analyses of DNA sequences obtained from the mitochondrial Cytochrome b gene in 690 individuals identified three clades corresponding to black-tailed deer, white-tailed deer, or a unique combination of both white-tailed deer and mule deer. White-tailed deer and mule deer diverged from a common ancestor of approximately 3.13 mya followed by an ancient hybridization event of approximately 1.32 mya, in which the white-tailed deer mitochondrial genome was “captured” by mule deer. This hybridization event produced a novel haplogroup for white-tailed deer and mule deer located west of the Appalachian Mountains and east of the Cascade Range, south to Veracruz, Mexico, and north to the Yukon Territory, Canada. The ancestral mule deer-like mitochondrial genome appears to be restricted to black-tailed deer distributed along the western portion of the Cascade and Sierra Nevada Ranges of the United States and Canada, whereas the ancestral white-tailed deer-like mitochondrial genome is restricted to the eastern United States and portions of Latin America and Caribbean regions. The “captured mitochondrial genome” has continued on an independent evolutionary trajectory and represents a unique and broadly distributed haplogroup that is 7.25% and 2.84% different from the ancestral mule deer and ancestral white-tailed deer haplogroups, respectively.

Snow track counts for density estimation of mammalian predators in the boreal forest

Context Methods for estimating density of meso-carnivores in northern ecosystems are labour intensive and expensive to implement if mark–recapture and radio collaring are used. One alternative is to count tracks in the snow along transects as an index of density, but this method has been criticised as imprecise and lacking validation. Aims We aimed to examine the utility of track counts along snowmobile trails in the snow for measuring changes in populations of Canada lynx and coyotes in the boreal forest of north-western Canada. Methods We compared winter track counts of Canada lynx at three study sites and of coyotes at one site with concurrent estimates of density based on locations of radio-collared animals and estimates of numbers of uncollared animals from three 7–9-year studies in the Yukon and Northwest Territories, during a period of cyclical population fluctuations. Key results Snow track counts were positively correlated (r2 = 0.83) with density of Canada lynx, estimated by live trapping and radio collaring in the three survey areas. Coyotes also showed a clear relationship (r2 = 0.80) between known density and snow track counts, but track counts were strongly affected by season, with much higher counts in the early winter when snow was shallower. This indicates the need to control for season or snow depth when using track counts as indices of coyote abundance. We recommend sample sizes of at least 10 track counts per winter along a 25-km transect to maximise precision. Conclusions Snow track counts are a relatively simple, inexpensive method of concurrently tracking abundance of multiple species of meso-carnivores. These data indicate that track counts may be reliably used to monitor trends in numbers, but we suggest site-specific validation of the regressions reported here between tracks and animal abundance are required to translate these indices into estimates of density. Implications Track counts have the potential to be an affordable alternative to more intensive methods of monitoring trends in abundance of medium-sized mammals, for purposes such as management of harvest or to measure the success of programs to increase or reduce population abundance.

Fueling Resistance

<i>Fueling Resistance</i>

Evidence for Pleistocene gene flow through the ice-free corridor from extinct horses and camels from Natural Trap Cave, Wyoming

Natural Trap Cave (Bighorn Mountains, Wyoming) preserves an abundance of fossil remains from extinct Late Pleistocene fauna and is situated near a past migration route that likely connected populations in Eastern Beringia and the contiguous US—the ice-free corridor between the Cordilleran and Laurentide icesheets. Some palaeontological evidence supports a correspondingly high affinity between fauna recorded in Natural Trap Cave and Eastern Beringia versus elsewhere in the contiguous US, but this hypothesis has not yet been extensively tested using genetic data. In the present study, we analysed 16 horse specimens and one camel specimen from Natural Trap Cave. Of the horse specimens we analysed, we obtained 10 unique and previously unreported mitochondrial haplotypes belonging to two distinct (extinct) genetic clades—two haplotypes corresponded to a caballine horse (Equus sp.) and eight corresponded to the stilt-legged horse (Haringtonhippus francisci). With only one exception, it appears these newly sequenced individuals all shared a common ancestor more recently with Eastern Beringian individuals than with others from the contiguous US. In addition, mitochondrial data from a specimen assigned to Camelops sp. revealed that it shares a closer affinity with specimens from the Yukon Territory than those from Idaho or Nevada, though all appear to belong to a single species (“yesterday's camel”; Camelops cf. hesternus). Together, these results are consistent with a high level of genetic connectivity between horse and camel populations in the Bighorn Mountains and Eastern Beringia during the Pleistocene.

Tectonic Underplating and Dismemberment of the Maclaren‐Kluane Schist Records Late Cretaceous Terrane Accretion Polarity and ~480 km of Post‐52 Ma Dextral Displacement on the Denali Fault

AbstractTerrane accretion introduces irregular geometry and allochthonous material to obliquely convergent margins, which create opportunities to quantify strike‐slip displacement along otherwise margin‐parallel fault systems. We present new bedrock geologic mapping and U‐Pb and40Ar/39Ar geochronology from the Alaska Range suture zone in the eastern Alaska Range, which confirm a long‐hypothesized correlation between the Maclaren Glacier metamorphic belt (Alaska, USA) and the Kluane metamorphic assemblage (Yukon Territory, Canada) across the right‐lateral Denali fault. The new data inform a palinspastic reconstruction showing that the dissected metamorphic belts and associated plutons record ~480 km of dextral displacement along the Denali fault since ca. 52 Ma. Before strike‐slip separation, the Maclaren‐Kluane schist formed by west‐vergent forearc underplating in the waning stage of the ca. 100–90 Ma arc built upon the Yukon‐Tanana terrane. The prograde structural and metamorphic evolution of the Maclaren‐Kluane schist records the final collision of the Wrangellia composite terrane at ca. 75–65 Ma along a set of east‐dipping thrust shear zones, which we infer to record the polarity of the Late Cretaceous plate boundary between the composite terrane and North America. Paleogene extension partially exhumed the schists to the upper crust and may be a consequence of regionally distributed strike‐slip faulting at that time. Localization of the modern Denali fault after ca. 52 Ma dismembered the schists and four neighboring belts of plutonic, metasedimentary, and volcanic rocks. The transition to Yakutat oblique flat slab subduction at ca. 30–25 Ma marks the onset of transpressional deformation in the Denali fault system, which reactivated Late Cretaceous collisional structures bounding the Maclaren schist. Neogene reactivation of the Totschunda fault reduced strike‐slip motion on the Denali fault east of the Denali‐Totschunda intersection and continues to transfer residual plate boundary slip onto the Denali fault west of the intersection. Key outcomes of our synthesis include: (a) Much of the ~480 km of displacement on the Denali fault accumulated after strike‐slip on the neighboring Tintina and Border Ranges fault systems had largely shut down; (b) The modern Denali fault system should not be grouped with strike‐slip faults credited with large‐scale margin‐parallel transport of Cordilleran terranes in the Cretaceous. Instead, a poorly understood proto‐Denali fault system may be a candidate for large‐scale Cretaceous translation; and (c) the longevity (≥33 Myr) of the highly localized Denali fault master strand (≤1 km wide) implies that it occupies a major mechanical boundary that penetrates the lithosphere.

Density estimates for Canada lynx vary among estimation methods

AbstractUnbiased population density estimates are critical for ecological research and wildlife management but are often difficult to obtain. Researchers use a variety of sampling and statistical methods to generate estimates of density, but few studies have compared estimates across methods. During 2016–2017, we surveyed Canada lynx (Lynx canadensis) in southwestern Yukon Territory, Canada, using track transect counts, hair snares, camera traps, live traps, and Global Positioning System (GPS) collars. From these data, we estimated lynx density with two linearly scaled count methods, one spatial mark–recapture method, three spatial mark–resight methods, and one cumulative‐time method. We found up to fivefold variation in point density estimates despite adhering to method requirements and assumptions in a manner consistent with other studies. Our results highlight the dependency of density estimates on sampling process and model assumptions and demonstrate the value of careful and unbiased sampling design. Further research is needed to fully assess the accuracy and limitations of the many wildlife density estimation methods that are currently in use so that techniques can be appropriately applied to typical study systems and species.

\u201cThe system is well intentioned, but complicated and fallible\u201d interviews with caregivers and decision makers about palliative care in Canada

BackgroundCanadian palliative care (PC) philosophy seeks to support individuals in a person-centered and sensitive manner. Unfortunately, philosophy does not necessarily translate into practice and this divide may leave patients without appropriate care at the end of life, causing distress for some families. The primary goal of the study was to identify key factors affecting perceptions of quality PC from the perspective of informal caregivers and decision makers (e.g., program managers) and to understand how their experiences within the health care system may have influenced their perceptions.MethodsNine caregivers and 11 decision makers from Yukon Territory, British Columbia, Alberta, Ontario, & Nova Scotia shared their experiences in PC via interview or focus group. Audio recordings were transcribed verbatim and qualitatively analyzed for themes.ResultsThree themes emerged, including the Caregiver as Anchor, Bewildering System, and Patient, Caregiver, and Family-Centered Care. While these results resembled other studies on caregivers and individuals receiving PC, the present study also uncovered systemic concerns. There was agreement between the two participant groups across most subthemes, however only caregivers reported feelings of being trapped by the health care system and a general lack of respect from health care professionals. Additionally, caregivers stressed the importance of preserving some sort of normalcy in daily life despite the individual’s illness.ConclusionsCaregivers are critical. The health care system expects them to help a great deal, but they often do not feel supported or respected and the system is lacking the capacity and resources to meet their needs while they are grieving loss and struggling to meet demands.

Hydradephaga (Coleoptera: Amphizoidae, Dytiscidae, Gyrinidae, Haliplidae) of the Alaska-Yukon region: new records, distributions and faunal compositions

The Amphizoidae, Dytiscidae, Gyrinidae and Haliplidae (Coleoptera: Adephaga of Alaska (USA) and the Yukon Territory (Canada) were surveyed during the years 1994, 2016, 2017 and 2019. By adding specimens collected through the Arctic Shorebird Demographic Network survey and those from the collection of the University of Alaska, Fairbanks, a total of 5305 individuals are newly reported, which substantially expand our distributional knowledge of these families from the Alaska-Yukon region. Seventeen species are newly reported from Alaska; three from the Yukon Territory. Following this study 160 species are now recorded for the Alaska-Yukon region (136 in Alaska and 138 in Yukon territory). The Nearctic component of the fauna is made up of 103 species (64.4%), the Holarctic component of 57 species (35.6%). Most species (103, 64.4%) have a transcontinental distribution and are characteristic of the boreal and/or arctic ecozones whilst 57 species (35.6%), are recognised as species with western affinities. Eleven species are considered Beringian.

Horse exploitation by Beringian hunters during the Last Glacial Maximum

Genetic data suggest that the Native American founder population diverged from its Asian parent population about 25,000 years ago and was geographically isolated during the Last Glacial Maximum (LGM, ca. 21,000 years BP) before dispersing into North and South America as the ice sheets retreated. Archaeological evidence in eastern Siberia and Beringia is scarce, however. Although stone tools and cutmarks on bones dated to the LGM are reported at Bluefish Caves (Yukon Territory, Canada), the stratigraphic integrity of the site and the interpretation of the bone modifications have long been questioned by the scientific community. Here, we describe the results of a zooarchaeological study of the faunal assemblages from Pleistocene loess deposits of Bluefish Caves 1 and 2. Taphonomic analyses indicate that humans hunted a variety of prey at the site, including the Beringian horse (E. lambei), as early as 23,500 years BP. We discuss the significance of the site in debates about the timing of the initial peopling of North America and the role of human-hunters in megafaunal extinctions.

Evapotranspiration and energy partitioning across a forest-shrub vegetation gradient in a subarctic, alpine catchment

As a result of altitude and latitude amplified climate change, widespread changes in vegetation composition, density and distribution have been observed across northern regions. Despite wide documentation of shrub proliferation and treeline advance, few field-based studies have evaluated the hydrological implications of these changes. Quantification of total evapotranspiration (ET) across a range of vegetation gradients is essential for predicting water yield, yet challenging in cold alpine catchments due to heterogeneous land cover, including both boreal forest and shrub taiga ecosystems. Here, we present six years of surface energy balance components and ET dynamics at three sites along an elevational gradient in a subarctic, alpine catchment near Whitehorse, Yukon Territory, Canada. These sites span a gradient of thermal and vegetation regimes, providing a space-for-time comparison for future ecosystem shifts: 1) a low-elevation boreal white spruce forest (~12–20 m), 2) a mid-elevation subalpine taiga comprised of tall, dense willow (Salix) and birch (Betula) shrubs (~1–3 m) and 3) a high-elevation subalpine taiga with short, sparse shrub cover (<0.75 m) and moss, lichen, and bare rock. Eddy covariance instrumentation ran year-round at the forest and during the growing season at the two shrub sites. Total ET decreased and interannual variability increased with elevation, with mean May to September ET totals of 349 (±3) mm at the forest, 249 (±10) mm at the tall, dense shrub site, and 240 (±26) mm at the short, sparse shrub site. Comparatively, over the same period, ET:R ratios were the highest and most variable at the forest (2.19 ± 0.37) and similar at the tall, dense shrub (1.22 ± 0.09) and short, sparse shrub (1.14 ± 0.05) sites. Our results suggest that advances in treeline will increase overall ET and lower interannual variability; however, the large growing season water deficit at the forest indicates strong reliance on soil moisture from late fall and snowmelt recharge. In contrast, ET was considerably less at the cooler higher elevation shrub sites, which exhibited similar ET losses over 6 years despite differences in shrub height and abundance. ET rates between the two shrub sites were similar throughout the year, except during the peak growing season. Greater interannual variability in ET at the short, sparse shrub site indicates the reduced influence of vegetation controls on ET. Results suggest that predicted changes in vegetation type and structure in northern regions will have a considerable impact on water partitioning and will vary in a complex way in response to changing precipitation timing, phase and magnitude, growing season length, and vegetation snow and rain interactions.

Simulating site-scale permafrost hydrology: Sensitivity to modelling decisions and air temperature

To predict future hydrological cycling in permafrost-dominated regions requires consideration of complex hydrological interactions that involve cryospheric states and fluxes, and hence thermodynamics. This challenges many hydrological models, particularly those applied in the Arctic. This study presents the implementation and validation of set of algorithms representing permafrost and frozen ground dynamics, coupled into a physically based, modular, cold regions hydrological model at two tundra sites in northern Yukon Territory, Canada. Hydrological processes represented in the model include evapotranspiration, soil moisture dynamics, flow through organic and mineral terrain, ground freeze–thaw, infiltration to frozen and unfrozen soils, snowpack energy balance, and the accumulation, wind redistribution, sublimation, and canopy interception of snow. The model was able to successfully represent observed ground surface temperature, ground thaw and snow accumulation at the two sites without calibration. A sensitivity analysis of simulated ground thaw revealed that the soil properties of the upper organic layer dominated the model response; however, its performance was robust for a range of realistic physical parameters. Different modelling decisions were assessed by removing the physically based algorithms for snowpack dynamics and ground surface temperature and replacing them with empirical approaches. Results demonstrate that more physically based approaches should be pursued to reduce uncertainties in poorly monitored environments. Finally, the model was driven by three climate warming scenarios to assess the sensitivity of snow redistribution and ablation processes and ground thaw to warming temperatures. This showed great sensitivity of snow regime and soil thaw to warming, even in the cold continental climate of the northwestern Canadian Arctic. The results are pertinent to transportation infrastructure and water management in this remote, cold, sparsely gauged region where traditional approaches to hydrological prediction are not possible.

Use of artificial-substrate samplers to identify relations between periphytic diatom community composition and hydro-limnological conditions in shallow lakes of Old Crow Flats, Yukon Territory (Canada)

Use of artificial-substrate samplers to identify relations between periphytic diatom community composition and hydro-limnological conditions in shallow lakes of Old Crow Flats, Yukon Territory (Canada)

Geophysical reassessment of the role of ancient lineaments on the development of the western Laurentian margin and its sediment-hosted Zn–Pb deposits, Yukon and Northwest Territories, Canada

A new three-dimensional (3D) inversion strategy is applied to new compilations of gravity and magnetic data to reassess the role of crustal lineaments in the development of the western Laurentian margin, Selwyn Basin, and associated sediment-hosted zinc–lead (Zn–Pb) deposits. The region’s history is obscured by multiple tectonic overprints, including terrane accretion, plutonism, and thrust faulting. Regionally continuous, broadly northeast-trending crustal lineaments, including the Liard line, Fort Norman structure, and Leith Ridge fault, were interpreted as having had long-standing influence on craton, margin, and sedimentary basin development. An east–northeast-trending lineament, Mackenzie River, traced from the Misty Creek Embayment to Great Bear Lake, is interpreted as the southern edge of a cratonic promontory. The location of the Liard line, associated with a transfer fault that bounds the Macdonald Platform promontory, is refined. New geophysical results support the continuity of the Fort Norman structure below the Selwyn Basin, but limited evidence exists for the Leith Ridge fault in this area. A northwest-trending lineament that bounds the craton is interpreted as a crustal manifestation of lithospheric thinning of the Laurentian margin, as echoed by a change in the depth of the lithosphere–asthenosphere boundary. The structure delimits the eastern extent of mid- to Late Cretaceous granitic intrusions and is straddled by Mississippi Valley-type Zn–Pb occurrences, following their palinspastic restoration. Clastic-dominated Zn–Pb occurrences are aligned along another northwest-trending lineament interpreted to be associated with a shallowing of lower crustal rocks.

Rapid shrub expansion in a subarctic mountain basin revealed by repeat airborne LiDAR

As a consequence of increasing temperatures, a rapid increase in shrub vegetation has occurred throughout the circumpolar North and is expected to continue. Rates of shrub expansion are highly variable, both at the regional scale and within local study areas. This study uses repeat airborne LiDAR and field surveys to measure changes in shrub vegetation cover along with landscape-scale variations in a well-studied subarctic headwater catchment in Yukon Territory, Canada. Airborne LiDAR surveys were conducted in August 2007 and 2018, whereas vegetation surveys were conducted in summer 2019. Machine learning classification algorithms were used to predict shrub presence/absence in 2018 based on rasterized LiDAR metrics, with the best-performing model applied to the 2007 LiDAR to create binary shrub cover layers to compare between survey years. Results show a 63.3% total increase in detectable shrub cover >= 0.45 m in height between 2007 and 2018, with an average yearly expansion of 5.8%. These changes were compared across terrain derivatives to quantify the influence of topography on shrub expansion. Terrain comparisons show that shrubs are located in and are preferentially expanding into lower and flatter areas near stream networks, at lower slope positions and with a higher potential for topographic wetness. Overall, the findings from this research reinforce the documented increase in pan-Arctic shrub vegetation in recent years, quantify the variation in shrub expansion over terrain derivatives at the landscape scale, and demonstrate the feasibility of using LiDAR to compare changes in shrub properties over time.

Ogilvie Platform Composite Tectono-Sedimentary Element

Abstract The Ogilvie Platform Composite Tectono-Sedimentary Element (CTSE) occupies an area of about 68 000 km 2 in the northern part of the Yukon Territory of Canada, and includes all Paleozoic- and Triassic-aged strata between a base of Cambrian unconformity and a base of Jurassic and Cretaceous unconformity. This cratonic platform is composed of two lithologically distinct sedimentary successions: a lower suite of peritidal to shallow-subtidal, carbonate-dominated, Cambrian–Middle Devonian-aged units; and an upper succession of siliciclastic-dominated alluvial fan, shelf delta, nearshore, slope and basinal strata of Middle Devonian–Late Permian and Triassic age. The lower succession is composed of a synrift tectono-sedimentary element (TSE) and an overlying passive continental-margin TSE. The upper succession is composed of an Ellesmerian orogenic foreland TSE and a syn-epeirogenic TSE. The total discovered oil reserve within the Ogilvie Platform is estimated to be 1.757 × 10 6 m 3 (11.05 MMbbl) and the total discovered gas reserve is estimated to be 2.376 × 109 m 3 (83.7 Bcf) in four oil and gas pools. A variety of stratigraphic and structural trap types have been assessed to contain additional conventional hydrocarbon reserves, with a total mean potential of 33.4 × 10 6 m 3 (210.1 MMbbl) of oil and 33.4 × 10 9 m 3 (2.63 Tcf) of gas. The organic-rich shale and siltstone-dominated petroleum source-rock units, such as within the Road River Group, the Canol and Ford Lake formations, and organic-rich strata within the Hart River and Blackie formations, are also prospective for large reserves of unconventional oil and gas, and have yet to be formally assessed.