Caribou Forage Research Articles

Climate Warming Impacts Tuttuk (Caribou) Forage Availability in Tongait (Torngat) Mountains, Labrador

Tuttuk [caribou (Rangifer tarandus)] populations are in decline across Canada, making them a major conservation concern for Inuit of Nunatsiavut (Northern Labrador) and Nunavik (Northern Quebec). This study investigates changes to caribou forage over 14-years at two tundra sites in northern Nunatsiavut, Labrador. We ask: 1) How much of the total vegetation is suitable caribou forage and how has this changed with time and experimental warming; and 2) Which forage species are most affected by recent climate change? At control and warming plots, we identified selected, edible, and avoided caribou forage based on published literature, and modeled observed changes in forage availability. We found that the relative frequency of selected winter forage was lower than summer forage at both sites. Caribou appear to be more forage limited in the winter than summer, and birch (Betula spp.), and ericaceous shrub species (Vaccinium spp.), increased over time. Our research provides valuable insight into recent changes in caribou forage availability and develops a novel methodology that can be applied across other caribou ranges. This knowledge will inform conservation and management measures by helping identify possible forage limitations and can contribute to recovery targets across Nunatsiavut and ultimately the social-ecological resilience of northern communities.

Can partial-cut harvesting be used to extend the availability of terrestrial forage lichens in late-seral pine-lichen woodlands? Evidence from the Lewes Marsh (southern Yukon) silvicultural systems trial

In northern British Columbia and southern Yukon woodland, caribou forage extensively on terrestrial lichens, predominately mat-forming Cladina species in late-successional pine-lichen woodlands. Many of these stands are now reaching a point in their development where lichen abundance declines as feather-moss mats increase. We evaluated the response of forest floor plant communities in pine-lichen woodlands from the southern Yukon Lewes Marsh partial-cutting trial 8 years after harvesting. Photoplot results documented a major decline (>60% ± 5.6% SE) in the mean surface area of existing large clumps of C. mitis in control (unharvested) treatments, whereas the mean surface area of large C. mitis clumps declined by 28% (±15% SE) in the one-third basal-area removal and showed an increase of 13.5% (±25% SE) in the two-thirds basal-area removal. Line intercept transects documented no changes in overall stand-level lichen abundance between pre-harvest (2012) and post-harvest (2021) measurements, while feather-moss mats and dwarf shrubs showed declines and increases, respectively, in partial-cutting harvest plots. Stand thinning may provide a bridging strategy to extend the period of forage lichen availability in late-seral pine-lichen woodlands, an important consideration in landscapes where increasing severity and frequency of fires are changing the seral-state distribution of caribou habitat.

Terrestrial lichen caribou forage transplant success: year 5 and 6 results

The southern mountain caribou—a subpopulation of caribou found in British Columbia—is listed on Schedule 1 of the Federal Species at Risk Act as Threatened. Woodland caribou are diet specialists, relying on Cladonia subgenus Cladina lichen as a primary food source during winter months. Lichens are burned along with trees and other vegetation during stand‐replacing wildfire events, a natural disturbance in caribou ranges. In an attempt to accelerate the return of post‐fire forests to productive caribou winter terrestrial lichen habitat, this study examined the survival and cover of three species of transplanted lichens in a post‐wildfire environment in north central British Columbia, Canada, both with and without forest litter amendments. Chlorophyll fluorescence was used to evaluate lichen survival by measuring potential photosynthetic activity. The results of this study demonstrate that transplanted fragments and mats of Cladonia subgenus Cladina had survived 5 and 6 years after being transplanted within a post‐wildfire environment, and had significantly greater percent cover when compared to the controls. The Fv/Fm results indicated that transplanted lichens survived, regardless of species, propagule type, or whether amendments were applied.

A New U-Net Based Convolutional Neural Network for Estimating Caribou Lichen Ground Cover from Field-Level RGB Images

High-quality ground-truth data are critical for developing reliable Earth Observation (EO) based geospatial products. Conventional methods of collecting these data are either subject to an unknown amount of human error and bias or require extended time in the field to complete (i.e., point-intercept assessments). Digital photograph classification (DPC) may address these drawbacks. In this study, we first assess the performance of a DPC method developed through licensed software to estimate ground cover percentage (%) of bright lichens, a critical caribou forage in fall and winter when other food resources are scarce. We then evaluate the feasibility of replicating this workflow in an open-source environment with a modified U-net model to improve processing time and scalability. Our results indicate that DPC is appropriate for generating ground-truth data in support of large-scale EO-based lichen mapping within the boreal forests of eastern Canada. Our final open-sourced classification model, Lichen Convolutional Neural Network (LiCNN), is comparably accurate yet more efficient than the licensed workflow. Therefore, the LiCNN approach successfully addresses the mentioned shortcomings of conventional ground-truth data collection methods efficiently and without the need for specialized software.

Short‐term effects of summer warming on caribou forage quality are mitigated by long‐term warming

AbstractRapid Arctic climate change is leading to woody plant‐dominated ecosystems with potential consequences for caribou foraging and nutritional ecology. While warming has been clearly linked to shrub expansion, the influence of higher temperatures on variables linked to the leaf‐level quality of caribou forage is equivocal. Moreover, warming results in a complex set of ecosystem changes that operate on different timescales such as not only rapidly accelerating phenology, but also slowly increasing thaw depth and plant access to soil resources. Here, we compare changes in leaf nitrogen (N) concentration, digestibility, and protein‐precipitating capacity (PPC) in short‐term (i.e., <1–2 summers) and long‐term (approximately 25 years) experimental warming plots with ambient temperature plots for three species commonly included in caribou summer diets:Salix pulchra(diamond‐leaf willow),Betula nana(dwarf birch), andEriophorum vaginatum(cottongrass). Short‐term warming modestly decreased leaf N concentration inB. nana.Long‐term and short‐term warming slightly increased the digestibility ofS. pulchra, but only short‐term warming increased digestibility inB. nana. Greater dry matter digestibility in both shrubs occurred through reductions in the lignin and cutin quantity in plant cells. Long‐term warming had no impact on PPC and equivocal impact on digestible protein ofB. nana. Overall, we found short‐term warming to be more impactful on forage quality than long‐term warming at Toolik Lake, Alaska. Apart from a long‐term warming reduction of approximately 13% in acid detergent lignin inS. pulchraandB. nana, other differences were only observed in the short‐term warming plots. Hence, our results indicate acclimation of plants to long‐term warming or possible negative feedback in the system to reduce warming effects. We suggest that warming summers may have a lesser effect on caribou forage than changes in winter precipitation or the influence of climate change on the abundance of critical species in the caribou diet.

Direct and Indirect Effects of Habitat Disturbances on Caribou Terrestrial Forage Lichens in Montane Forests of British Columbia

Cumulative effects of increased forest harvesting, mountain pine beetle (Dendroctonus ponderosae; MPB) outbreaks, and wildfire in low-elevation lodgepole pine (Pinus contorta) forests could limit long-term winter habitat supply for the northern group of southern mountain caribou (Rangifer tarandus). In a 17 year longitudinal study of vegetation remeasurements at eight sites in north-central and west-central British Columbia (BC), we assessed responses of terrestrial caribou forage lichen abundances to nine forest harvesting treatments and one prescribed burn 8–14 years following treatment, as well as to MPB attack. Overall, after initially declining following forest harvesting, mean forage lichen abundance increased between 1 and 2 years post-harvest and 13 and 14 years post-harvest at 10 of 11 site/treatment combinations. Mean forage lichen abundance decreased following MPB attack at all sites. Biophysical factors influencing rates of lichen recovery post-disturbance include site type (transitional vs. edaphic), a reduction in favourable conditions for moss recovery, level of MPB attack, and both seasonal timing and method of forest harvesting. When considering effects of forest harvesting on forage lichens, objectives of silvicultural management strategies should focus on protecting and retaining terrestrial lichens at edaphic sites and on re-establishing terrestrial lichens at transitional sites.

Landscape features and caribou harvesting during three decades in Newfoundland

ABSTRACT Landscapes can influence the distribution of harvesting by influencing animal distribution and hunter access. For species like caribou, Rangifer tarandus, decades-long shifts in abundance and distribution might alter such relationships, but few studies have been conducted at such scales. We examined relationships between landscape features and 21,380 harvest records of migratory caribou in Newfoundland during caribou population growth (1980s), cessation of growth (1990s), and decline (2000s). We focused on features hypothesized to influence the distributions of caribou and hunters: lichen landcover, roads, cutblocks, outfitter camps, power lines, and towns. We uncovered larger harvests by resident hunters of male and female caribou among lichen landcover, likely providing preferred caribou forage, and larger harvests by non-resident hunters of male caribou away from towns, reflecting the locations of outfitter camps. Only during later decades, resident harvests occurred nearer power lines and cutblocks, likely providing hunter access and reflecting risk-prone foraging by caribou. We surmise that the harvest was facilitated by open habitats, preferred by caribou, and anthropogenic features leading to hunter access, especially as the caribou population declined. Such knowledge at broad scales is increasingly important in an era of widespread disruption to landscapes.

Snowier winters extend autumn availability of high‐quality forage for caribou in Arctic Alaska

AbstractCaribou (Rangifer tarandus) rely on the short Arctic growing season to restore body condition, support the demands of lactation, and prepare for the long arctic winter, making them susceptible to even small changes in forage availability or quality. Body condition in the summer and autumn is linked to winter survival rates and fecundity in cows, critical factors in the productivity of caribou populations. Climate change predictions of warmer and wetter northern winters suggest increased snowfall over Alaska's North Slope, which has recently been verified between 1995 and 2017. However, a comprehensive analysis of how deeper snow will affect caribou forage quality is absent across Alaska. In this study, we quantify how snow depth alters the quality and seasonality of caribou forage using a long‐term (24 yr) International Tundra Experiment snow depth manipulation to evaluate how winter climate change scenarios may affect tussock tundra systems in northern Alaska. Deeper snow in prior winters leads to increases in growing season leaf N and digestible protein (DP) in deciduous shrubs (Salix spp. and Betula spp.) and graminoids (Carex spp. and Eriophorum spp.), but not evergreen dwarf shrubs (Rhododendron spp. and Vaccinium spp.). Dry matter digestibility varied among species with small differences (<5%) associated with snow depth. Most striking was the discovery that deeper snow in the prior winter increased the duration of DP levels above the minimum threshold for protein gain in caribou by as much as 25 d in Salix pulchra and 6–9 d in Betula nana and Carex bigelowii in late summer and early autumn. Consequently, deeper winter snow may provide an extended window of opportunity for foraging and the accumulation of lean body mass and fat reserves which promote winter survival and successful calving the following spring and potentially improve the productivity of caribou in northern Alaska.

Effects of dust deposition from diamond mining on subarctic plant communities and barren-ground caribou forage.

Dust produced from mining has the potential to reduce plant cover, alter plant communities, and increase metal concentrations in vegetation-changes that may affect the amount, type, and quality of forage for barren-ground caribou (Rangifer tarandus groenlandicus). We quantified dust deposition from Diavik Diamond Mine (Northwest Territories, Canada) and investigated the changes on forage quality, type, and quantity for caribou. From 2002 to 2016, dust deposition was measured, and vegetation cover and richness were assessed in permanent plots established adjacent to the mine and in reference areas 1-6km from the mine. Lichen was collected from areas up to 100km from the mine to determine metal concentrations. Dust deposition rapidly decreased within 4km of the mine. Plant communities adjacent to the mine (within 500m) had disproportionately increased cover of vascular plants and decreased bryophyte and lichen cover. Lichen sampled within 4km from the mine had greater metal concentrations than those sampled farther afield. Concentrations of Al in lichen collected within 40km of the mine exceeded safe exposure limits for consumption, assuming lichen comprised 100% of caribou diet. We conclude that dust deposition from mining is altering adjacent vegetation communities but that such changes to forage are unlikely to cause negative effects to caribou due to reduced lichen intake in summer and autumn, their migratory nature, and avoidance of mine-influenced areas. However, minimization and reclamation of mine-related disturbances will be important for maintaining sufficient quality forage and available habitat or space in caribou ranges.

Predicting patterns of terrestrial lichen biomass recovery following boreal wildfires

AbstractIncreased fire activity due to climate change may impact the successional dynamics of boreal forests, with important consequences for caribou habitat. Early successional forests have been shown to support lower quantities of caribou forage lichens, but geographic variation in, and controls on, the rates of lichen recovery has been largely unexplored. In this study, we sampled across a broad region in northwestern Canada to compare lichen biomass accumulation in ecoprovinces, including the Saskatchewan Boreal Shield, the Northwest Territories Taiga Shield, and Northwest Territories Taiga Plains, divided into North and South. We focused on the most valuable Cladonia species for boreal and barren‐ground caribou: Cladonia mitis and C. arbuscula, C. rangiferina and C. stygia, and C. stellaris and C. uncialis. We developed new allometric equations to estimate lichen biomass from field measurements of lichen cover and height; allometries were consistent among ecoprovinces, suggesting generalizability. We then used estimates of lichen biomass to quantify patterns of lichen recovery in different stand types, ecoprovinces, and with time following stand‐replacing fire. We used a hurdle model to account both for the heterogeneous nature of lichen presence (zero inflation) and for the range of abundance in stands where lichen was present. The first component of the hurdle model, a generalized linear model, identified stand age, stand type, and ecoprovince as significant predictors of lichen presence. With a logistic growth model, a measure of lichen recovery (time to 50% asymptotic value) varied from 28 to 73 yr, dependent on stand type and ecoprovince. The combined predictions of the hurdle model suggest the most rapid recovery of lichen biomass across our study region occurred in jack pine in the Boreal Shield (30 yr), while stands located in the Taiga Plains (North and South) required a longer recovery period (approximately 75 yr). These results provide a basis for estimating future caribou habitat that encompasses some of the large variation in fire effects on lichen abundance and vegetation types across the range of boreal and barren‐ground caribou in North America.

Mineral constraints on arctic caribou (Rangifer tarandus): a spatial and phenological perspective

AbstractArctic caribou (Rangifer tarandus) have the longest terrestrial migration of any ungulate but little is known about the spatial and seasonal variation of minerals in summer forages and the potential impacts of mineral nutrition on the foraging behavior and nutritional condition of arctic caribou. We investigated the phenology, availability, and mechanistic relationships of calcium, phosphorus, magnesium, sodium, potassium, iron, manganese, copper, and zinc in three species of woody browse, three species of graminoids, and one forb preferred by caribou over two transects bisecting the ranges of the Central Arctic (CAH) and Western Arctic (WAH) caribou herds in Alaska. Transects traversed three ecoregions (Coastal Plain, Arctic Foothills and Brooks Range) along known migration paths in the summer ranges of both herds. Concentrations of mineral in forages were compared to estimated dietary requirements of lactating female caribou. Spatial distribution of the abundance of minerals in caribou forage was associated with interactions of soil pH and mineral content, while temporal variation was related to plant maturity, and thus nitrogen and fiber content of forages. Concentrations of sodium were below caribou requirements in all forage species for most of the summer and adequate only on the Coastal Plain during the second half of summer. Phosphorus declined in plants from emergence to senescence and was below requirements in all forages by mid‐summer, while concentrations of copper declined to marginal concentrations at plant senescence. Interactions of sodium with potassium, calcium with phosphorus, and copper with zinc in forages likely exacerbate the constraints of low concentrations sodium, phosphorus, and copper. Forages on the WAH contained significantly more phosphorus and copper than forages collected on the CAH transect. We suspect that migrations of caribou to the Arctic Coastal Plain may allow parturient females to replenish sodium stores depleted by foraging inland through the long arctic winters, while also extending the availability of adequate phosphorus, if animals are able to selectively track emerging waves of forage.

Does Dust from Arctic Mines Affect Caribou Forage?

This study explores how dust from the Ekati Diamond Mine potentially affects the availability and quality of forage on the seasonal range of the Bathurst caribou herd. Understanding the effects of dust as a source of disturbance is important because the Bathurst caribou population has declined by 93% since the middle 1980s and there are reports that caribou in general may avoid mining projects. There are several challenges for quantifying dust impacts: 1) Natural variations (e.g., topography, natural disturbance, and soil pH) may also impact forage availability and quality for caribou. To minimize their masking effect, we stratified survey sites into seven land cover classes and selected the most populous class (i.e., the dwarf shrub) for assessing the impact. 2) Within class variation (e.g., the proportion of area covered by rocks where vascular plants and lichen do not grow) can further skew the analysis. We eliminated this problem by examining only the area not covered by rocks. 3) Coarse and fine suspended particulates have different spatial coverages, chemical compositions, and pH values. Consequently, their impacts on caribou forage can be different. To distinguish their impacts, we sampled two areas: transects from the Misery Haul Road that has been in active use vs. those from a rarely used spur road outside the Misery Camp. We sampled percent vegetation cover, soil pH, and dust on leaves along these transects during the summers of 2015 and 2016. Our results indicated that the amount of dust on leaves in a zone of ~1000 m from the Misery Haul Road was 3 - 9 times than that of background sites. The zone of reduced lichen percent cover was also about 1000 m. In contrast, these road dust-induced changes in caribou forage were not observed for the dust-free transect from the spur road.

Detecting continuous lichen abundance for mapping winter caribou forage at landscape spatial scales

Spatial variation of available food resources can be difficult to accurately quantify for wide ranging organisms at landscape scales. Lichens with usnic acid, a yellowish pigment, constitute a large portion of caribou winter diet across much of their range. We take a new approach of modeling lichen abundances by capitalizing on unique spectral characteristics of usnic acid lichens. We utilize a recently completed ground reference vegetation data set extending over 12,000km2 in Denali National Park and Preserve, Alaska to model the abundance of usnic lichen and other forage vegetation groups. Spectral signatures were obtained for more than 700 vegetation monitoring plots in Denali from Landsat 7 ETM+ imagery. We fit models of the absolute percent cover of vegetation groups corresponding to caribou diet items, with a focus on lichens. We used non-parametric multiplicative regression to capture the non-linear relationships between vegetation cover and spectral and environmental data. Different groupings of lichen cover were tried as response variables in addition to usnic lichens to see if other lichen color groups were more detectable. The best fitting lichen model was for usnic acid lichens, which explained 37% of the variation using only three predictors (elevation, bands 1 and 7). Elevation had a non-linear, double-humped shaped relationship to usnic lichen abundance while bands 1 and 7 were positively correlated with usnic lichen cover. These results support previous spectroradiometric ground measurements that indicated usnic lichens were distinctive at those wavelengths. Other vegetation groups had models that explained between 31% and 51% of the variation in cover. Maps of estimated abundance of usnic lichens and other vegetation groups covering the northern half of Denali were generated using our models. These maps enable the study of the role of food resources as a continuous resource in winter habitat selection by caribou, rather than assuming food as a coarser, categorical or thematic variable assigned to discrete areas of the landscape as has been done in most previous studies.

The influence of fire history on selection of foraging sites by barren-ground caribou

We used an information-theoretic model comparison approach to investigate the influence of forest stand attributes resulting from wildfire on the occupancy of winter habitats by barren-ground caribou (Rangifer tarandus groenlandicus) in the Northwest Territories, Canada. We used field data describing forest stand and understory attributes to develop multinomial regression models. These analyses identified a combination of ground cover type and tree volume (i.e., stand basal area) as best able to describe the observed selection of feeding sites. An observed increase in the percent ground cover of lichen had a positive influence on site selection, while an increase in the percent rock cover and basal area of conifer trees had a negative influence on selection of feeding sites by caribou. The most parsimonious regression model predicted site use with an accuracy of 87%. Lastly, we used published equations to determine the biomass of fruticose lichens on experimental and control sites classified as unburned. Our data indicated that fruticose lichen biomass on the winter range of the Bathurst herd of barren-ground caribou was high compared to winter habitats of caribou in Alaska and the Yukon Territory, and falls in the general range of lichen values reported for winter habitats of the more easterly Beverly herd, as well as portions of Saskatchewan, Manitoba, and Ungava. Overall, the analyses of feeding-site selection suggest that Bathurst caribou forage in areas with a high percentage cover and biomass of lichen, and that future increased incidence and severity of forest fires could cause a temporary decrease in the quality of winter habitat available to the Bathurst herd.

Permafrost and Peatland Evolution in the Northern Hudson Bay Lowland, Manitoba

The northern Hudson Bay lowland includes the largest area of frozen peat plateau bog in Canada. Polar bear denning habitat, caribou forage, carbon storage, and wetland drainage control provided by peat plateaus will be affected if post-Little Ice Age warming continues. Mapping and thermal modeling of frozen peat plateau stability indicate that permafrost peatlands are stable at a mean annual air temperature as warm as -3.5˚C. In the peat plateaus of the northern lowland, permafrost can be absent at the peat plateau margins where peat plateaus border fens or lakes. Here, insulating snow accumulations permit thawed conditions at mean annual air temperatures colder than -3.5˚C. Continued warming will result in expansion of thawed zones, subsidence at plateau margins, and even collapse of plateau surfaces, resulting in conversion to fen. This process has already occurred across north-central Manitoba, Saskatchewan, and Alberta since the end of the Little Ice Age, and there are signs that it is extending into the northern Hudson Bay lowland. Wave erosion of subsiding plateau borders at lake shorelines is also resulting in loss of peat plateau bog.

Influence of forage preferences and habitat use on 13C and 15N abundance in wild caribou (Rangifer tarandus caribou) and moose (Alces alces) from Canada

Stable isotope composition (δ13C and δ15N) of moose (Alces alces) and caribou (Rangifer tarandus) hair from the boreal forest of Jacques-Cartier Park and Côte-Nord (Québec) and arctic tundra of Queen Maud Gulf and Southampton Island (Nunavut) was investigated as an indicator of dietary preferences and habitat use. Values of δ13Chair and δ15Nhair in moose were consistently lower compared to those of caribou. This is consistent with the depletion in 13C and 15N in the plants preferred by moose, essentially browse (shrub and tree leaves), compared to caribou forage, which included significant amounts of graminoids, lichen and fungi. The δ13Chair values of caribou differed between closed boreal forest and open-tundra ecosystems. This pattern followed that expected from the canopy effect observed in plant communities. Variation in δ15Nhair values of caribou was probably linked to the effect of different climatic conditions on plant communities. This study underlines the potential of isotopic analysis for studies on diet and habitat selection within a pure C3 plant environment.

Forage Quality and Reindeer Productivity: Multiplier Effects Amplified by Climate Change

ABSTRACTWe investigated the effects of experimental manipulations of snowmelt on the flowering phenology and forage chemistry (digestibility and nitrogen concentration) of tussock cottongrass (Eriophorum vaginatum) on the Seward Peninsula, Alaska. Early snowmelt accelerated reproductive phenology by 11 days, and resulted in higher floral digestibility both early and late during inflorescence development. Nitrogen concentrations of inflorescences in late snowmelt plots were initially the highest among treatments, but decreased nearly 40% during inflorescence development. Thus, changes in climate that lead to changes in snow cover can alter both the timing of flowering and chemistry of Eriophorum and, consequently, its value as reindeer and caribou forage. We then used published relationships between forage chemistry and body weight gain of reindeer (White, 1983) to model the possible effects of altered forage chemistry on food intake and growth in reindeer. Model output shows that reindeer foraging on Eriophorum inflorescences may increase digestible dry matter intake twofold by selectively foraging on early-emergent inflorescences. The multiplicative effects of forage quality and food intake result in a near doubling in the rate of weight gain during this critical early spring period. Such increases in body weight gain have potentially great consequences for reindeer at both individual and population levels.

Slow Recovery of Lichen on Burned Caribou Winter Range in Alaska Tundra: Potential Influences of Climate Warming and Other Disturbance Factors

ABSTRACTLichen regeneration timelines are needed to establish sound fire management guidelines for caribou (Rangifer tarandus) winter range. Paired burned and unburned permanent vegetative cover transects were established after 1981, 1977, and 1972 tundra fires in northwestern Alaska to document regrowth of tundra vegetation including caribou forage lichens in the wintering range of Alaska’s largest caribou herd. Following fire, lichen had recovered very little compared to unburned transects (1% cover vs.15% cover) after 14 years. After 24 or 25 years, lichen cover in the burns remained low (3–4%), whether or not caribou were present during the recovery period. In addition, lichen cover on unburned transects at one study site had decreased from 14% to 6%. Shrub cover was higher on the burned plots than the unburned plots. Cover of cottongrass (Eriophorum vaginatum) initially increased following the fire and tussocks quickly became more vigorous than on paired unburned transects, remaining so for more than 14 years. Persistent changes in vegetation following fire likely reflect the cumulative impacts of seasonal caribou use and favorable growing conditions (warmer soils, longer growing season) for rooted vascular species during the recovery period. The actual recovery of forage lichens after fire on our study sites is slower than predictions based on ideal growth potential.

Potential net effects of climate change on High Arctic Peary caribou: Lessons from a spatially explicit simulation model

It is anticipated that climate change will have a major impact on High Arctic ecosystems. Peary caribou ( Rangifer tarandus pearyi) is a caribou subspecies endemic to the Canadian High Arctic. In the past four decades, population dynamics of Peary caribou have been subject to several population die-offs due to unfavorable winter weather with ice coating on the ground or thicker-than-usual snow cover. There is general consensus that such disturbance years may increase in frequency and severity as a result of climate change. However, there is also evidence that available forage may increase due to a longer and warmer growing season. In this study we assess the net effects of climate change with a spatially explicit simulation model calibrated with data from the Bathurst Island complex (BIC) in the Canadian High Arctic. In particular, we ask under which climate change scenarios populations depart from the current conditions and either suffer or benefit from changes in the climate. The model incorporates movement of caribou groups and annual primary productivity over 100 years. Based on the model we suggest that Peary caribou may experience significantly lower population die-offs during disturbance years if biomass increases by 50% as projected within the next 100 years and if the currently estimated proportion of inaccessible caribou forage during such disturbance events does not change with climate change. However, if forage inaccessibility in poor winters increases by more than 30% over the next 100 years, caribou may experience negative net effects of climate change. This is the first comprehensive modeling study on this species and therefore of particular importance for wildlife management and local Inuit who rely on caribou as part of their culture, identity, and diet.

Seedling response following partial cutting in lodgepole pine forests on caribou winter range in west-central British Columbia

Group selection and irregular group shelterwood silvicultural systems were applied to older lodgepole pine (Pinus contorta var. latifolia) forests in west-central British Columbia to determine their potential for maintaining northern caribou (Rangifer tarandus caribou) habitat. These silvicultural systems created small openings 15–30 m wide,which were planted with lodgepole pine and interior spruce (Picea glauca x Picea engelmannii) seedlings. Fifth-year survival and growth results indicate that either species could adequately regenerate the small openings created by partial cutting. Pine survival in the partial cuts (93–95%) was comparable to the clearcuts (94%). Pine height and height growth did not vary significantly between treatments; however, diameters were significantly larger in the clearcuts. After five years across all treatments, pine seedlings were 38–42 cm tall with diameters ranging from 7–11 mm. Spruce survival varied considerably between the clearcuts (35–98%) but was more consistent in the partial cuts (66–97%). Total height and height growth differed significantly among treatments, with the shortest spruce seedlings found in the clearcuts. Seedling diameter did not differ among treatments. Average fifth-year height ranged from 31 cm to 44 cm and diameters ranged from 7 mm to 9 mm. To maintain caribou habitat, species should be planted in similar proportions to the pre-harvest stand composition to avoid potential impacts on the terrestrial and arboreal lichens, which are important caribou forage. Key words: caribou, lodgepole pine, partial cutting, planted seedlings, interior spruce, group selection, irregular group shelterwood