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Grande Prairie, Canada

DeCesare N.J.,University of Montana | Hebblewhite M.,University of Montana | Bradley M.,Parks Canada | Hervieux D.,Sustainable Resource Development | And 2 more authors.
Journal of Animal Ecology

Summary: A central assumption underlying the study of habitat selection is that selected habitats confer enhanced fitness. Unfortunately, this assumption is rarely tested, and in some systems, gradients of predation risk may more accurately characterize spatial variation in vital rates than gradients described by habitat selection studies. Here, we separately measured spatial patterns of both resource selection and predation risk and tested their relationships with a key demographic trait, adult female survival, for a threatened ungulate, woodland caribou (Rangifer tarandus caribou Gmelin). We also evaluated whether exposure to gradients in both predation risk and resource selection value was manifested temporally through instantaneous or seasonal effects on survival outcomes. We used Cox proportional hazards spatial survival modelling to assess the relative support for 5 selection- and risk-based definitions of habitat quality, as quantified by woodland caribou adult female survival. These hypotheses included scenarios in which selection ideally mirrored survival, risk entirely drove survival, non-ideal selection correlated with survival but with additive risk effects, an ecological trap with maladaptive selection and a non-spatial effect of annual variation in weather. Indeed, we found positive relationships between the predicted values of a resource selection function (RSF) and survival, yet subsequently incorporating an additional negative effect of predation risk greatly improved models further. This revealed a positive, but non-ideal relationship between selection and survival. Gradients in these covariates were also shown to affect individual survival probability at multiple temporal scales. Exposure to increased predation risk had a relatively instantaneous effect on survival outcomes, whereas variation in habitat suitability predicted by an RSF had both instantaneous and longer-term seasonal effects on survival. Predation risk was an additive source of hazard beyond that detected through selection alone, and woodland caribou selection thus was shown to be non-ideal. Furthermore, by combining spatial adult female survival models with herd-specific estimates of recruitment in matrix population models, we estimated a spatially explicit landscape of population growth predictions for this endangered species. © 2013 British Ecological Society. Source

Hopkinson C.,Wilfrid Laurier University | Collins T.,Destiny Resources | Anderson A.,Sustainable Resource Development | Pomeroy J.,University of Saskatchewan | Spooner I.,Acadia University
Canadian Water Resources Journal

This study illustrates the potential to combine LiDAR remote sensing and GIS techniques for the purpose of estimating instantaneous winter snowpack volume within the mountainous Elbow River Watershed (ERW) upstream of Calgary, Alberta. Two LiDAR (Light Detection and Ranging) datasets, one during snow-free and the other during late winter were used to evaluate a procedure for snow depth sampling. These data were also used to classify terrain and canopy cover attributes to enable snow depth estimation in areas that were not directly sampled but for which equivalent land classifications could be derived via other means. The mean snow depth from 1675 field measurements collected coincident with the winter LiDAR survey (late March, 2008) in snow-covered areas only was 0.28 m (σ = 0.27 m). The mean LiDAR-based snow depth in snow-covered areas was comparable with the field values at 0.26 m (σ = 1.2 m), or 0.18 m when averaged across both snow-covered and snow-free areas. Using field measurements of snow density, a GIS routine was employed to estimate total watershed snow water equivalent (SWE) from ten snow accumulation units (SAUs) using elevation, aspect and canopy cover. The total watershed SWE estimate was 46.0 × 106 m3. This volume of water can also be expressed as 0.058 m of water depth across the entire basin, or approximately 18% of the total 2008 runoff yield. Further work is needed to improve LiDAR-based snow depth estimation in areas of shallow snowpack where the influence of noise in the data is highest and to optimize the methods of sampling and extrapolation. At the present level of airborne LiDAR sophistication, positional uncertainties in LiDAR data (though small) are such that high confidence in the watershed snowpack volume estimate, would only be achieved during deep snowpack years; which also tend to be the years where accurate data are least required. However, given the availability of LiDAR base maps is ever growing, and the accuracy and costs associated with the technology are constantly improving, this approach to snow depth sampling has the potential to become a useful tool to support headwater snowpack resource assessment in water-stressed regions of Canada. © 2012 Canadian Water Resources Association. Source

Anderson A.E.,Sustainable Resource Development | Anderson A.E.,University of Calgary | Weiler M.,Albert Ludwigs University of Freiburg | Alila Y.,University of British Columbia | Hudson R.O.,University of British Columbia
Hydrological Processes

Characterizing zones of a watershed based on the water table is used to understand and predict internal watershed processes. In watersheds dominated by lateral preferential flow, the water table response typically shows a distinct hydraulically limited pattern. This response is characterized by a capping of the rising water table when the lateral preferential flow features are activated and subsurface flow still increases. We expected that this response would be related to the contributing area since nearby hillslope excavations showed that the development of preferential flow network was positively correlated with the contributing area. The watershed was stratified into three predetermined zones and installed 25 piezometers to measure the water table dynamics. The objectives were (1) to characterize the water table-runoff relationship, (2) to prove preferential flow by observable characteristics and (3) to test the feasibility of identifying areas within a watershed that are dominated by lateral preferential flow. Watershed zones were not well defined and there was no strong relationship between the hydraulically limited response and observable watershed characteristics. Although zones might still be useful for grouping the hillslope processes, the piezometric response may not be an appropriate indicator for mapping the watershed into areas with runoff dominated by lateral preferential flow. Copyright © 2010 John Wiley & Sons, Ltd. Source

Walia A.,University of British Columbia | Guy R.D.,University of British Columbia | White B.,Sustainable Resource Development
Tree Physiology

Western hemlock (Tsuga heterophylla [Raf.] Sarg.) is a major component of temperate rainforests in coastal British Columbia. Forest fertilization can enhance the growth of forest trees, but results are inconsistent for western hemlock. We investigated the relationship between δ13C (foliage and stemwood), growth response and tree nutritional status in this species. To establish a sampling protocol for stemwood, we first assessed spot-to-spot variation around and along the bole, which exceeded 1‰. We utilized the reaction wood (high lignin content) and adjacent normal wood in two curved western hemlock stems to evaluate whether this variation was related to wood composition. There was a consistent 3.43‰ difference between lignin and holocellulose, but the isotopic mass balance of whole wood was conserved and, therefore, did not vary with lignin content. Therefore, extraction of cellulose or holocellulose prior to analysis can introduce (not remove) bias. In a detailed study of a third stem, circumferential and longitudinal variation in δ13C was associated with spiral grain indicating limited physiological mixing of isotopic signatures originating from the crown. Wood was subsequently pooled from four cardinal positions around each stem. Eight even-aged western hemlock stands were selected and fertilized with different combinations of nitrogen (N), phosphorous (P) and a blend of S, K, Mg, Zn and Cu. Fertilization was effective in increasing foliar N, P, K and S depending on treatment. At the end of the first growing season after fertilization, the effect of treatments on foliar δ13C was nearly significant (P = 0.054), but did not persist into a second year. Effects on tree-ring δ13C were more obvious and persisted for about 3 years, averaging ∼0.2-0.4‰ over this period, depending on treatment. Combinations of N, P and blend had the greatest effect, consistent with relative increases in basal area increment. Effects of fertilizer additions on δ13C, though clear, were superimposed on larger site and annual weather-related patterns in δ13C. Large tree-to-tree variation in δ13C was positively correlated with basal area increment, both before and after treatment imposition, suggesting that high water-use efficiencies are associated with greater growth. © The Author 2010. Published by Oxford University Press. All rights reserved. Source

Cortini F.,Natural Resources Canada | Filipescu C.N.,Natural Resources Canada | Groot A.,Natural Resources Canada | MacIsaac D.A.,Natural Resources Canada | Nunifu T.,Sustainable Resource Development

We investigated the relationship of stem diameter to tree, site and stand characteristics for six major tree species (trembling aspen, white birch, balsam fir, lodgepole pine, black spruce, and white spruce) in Alberta (Canada) with data from Alberta Sustainable Resource Development Permanent Sample Plots. Using non-linear mixed effects modeling techniques, we developed models to estimate diameter at breast height using height, crown and stand attributes. Mixed effects models (with plot as subject) using height, crown area, and basal area of the larger trees explained on average 95% of the variation in diameter at breast height across the six species with a root mean square error of 2.0 cm (13.4% of mean diameter). Fixed effects models (without plot as subject) including the Natural Sub-Region (NSR) information explained on average 90% of the variation in diameter at breast height across the six species with a root mean square error equal to 2.8 cm (17.9% of mean diameter). Selected climate variables provided similar results to models with NSR information. The inclusion of nutrient regime and moisture regime did not significantly improve the predictive ability of these models. © 2011 by the authors. Source

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