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North Vancouver, Canada

Thomas K.E.,University of Waterloo | Hall R.I.,University of Waterloo | Scrimgeour G.J.,Parks Canada Agency
Environmental Monitoring and Assessment | Year: 2013

Assessments of stream condition using benthic algal communities have traditionally relied on taxonomy-based approaches to compare community structure at sites exposed to a stressor versus reference sites. Taxonomy-based methods are often effective, but they require high levels of training and are relatively time consuming and expensive. We examined the utility of assessing stream biological condition using algal pigments. We used gradient and control-impact study designs in 2008 and 2009 to compare the extent that algal pigments versus taxonomic descriptors of algal community structure varied along a 10.5-km stretch of the Flat River (South Nahanni River watershed, NWT, Canada) encompassing a gradient of nutrients and metals at sites upstream, adjacent to and downstream of a northern metals mine. We also calculated costs to quantify algal pigments relative to taxonomy-based methods. Multivariate analyses (ANOSIM tests, redundancy analysis) identified that pigment concentrations from benthic algal samples differed significantly (p < 0.05) between non-exposed and exposed river sites and were related to variations in water physico-chemical conditions. By contrast, community composition determined from taxonomy-based enumeration to the Order and Family levels did not differ significantly between non-exposed and exposed sites, and relations with water physico-chemical conditions were weaker and inconsistent between the study years. In-house costs to quantify algal pigments were lower than commercial rates to describe community structure using taxonomy. Thus, our data suggests that analysis of benthic algal pigments represents a viable and cost-effective bio-monitoring method for assessing anthropogenic effects on stream condition that merits further evaluation. © 2013 Springer Science+Business Media Dordrecht. Source


Roy-Leveillee P.,Carleton University | Burn C.R.,Carleton University | Mcdonald I.D.,Parks Canada Agency
Permafrost and Periglacial Processes | Year: 2014

Old Crow Flats is a 5600 km2 glaciolacustrine plain that straddles the forest-tundra ecotone in northern Yukon. Continuous taiga corridors occur in the entrenched river valleys, where annual mean ground temperatures (Tg) at the depth of zero annual amplitude at two locations were -3.1 and -4.0oC in 2013. On the Flats, the vegetation cover is patchy, and Tg varied between -5.1 and -2.6oC. Annual mean near-surface permafrost temperatures (Tps) measured on the Flats between 2008 and 2011 in patches of taiga, tall shrubs and low shrubs were correlated with local snow depth. Snow depth was controlled by vegetation height if the snow supply was not limited, for example, where low shrubs and large lakes dominate the landscape. In this setting, snow depths and, hence, Tps in taiga patches were higher (-2.6 to -2.9oC) than in the surrounding shrub vegetation (-3.5 to -5.5oC). Where taiga patches were more extensive, redistributed snow was trapped at the patch edge and Tps in taiga was lower (-4.1 to -4.3oC) than in the surrounding shrub patches (-3.2 to -3.6oC). The permafrost temperature field is heterogeneous under patchy vegetation in the forest-tundra ecotone. Our data suggest that it is governed by both the snow-holding capacity of local vegetation patches and the spatial configuration of vegetation in the surrounding landscape, which controls snow supply. © 2014 John Wiley & Sons, Ltd. Source


Perrakis D.D.B.,Parks Canada Agency | Agee J.K.,University of Washington | Eglitis A.,U.S. Department of Agriculture
Natural Areas Journal | Year: 2011

Forests dominated by old growth ponderosa pine (Pinus ponderosa Dougl.) at Crater Lake, Oregon, have been viewed as good candidates for restoration via prescribed burning. Previous burn experiments in this ecosystem observed that ponderosa pine typically survived burning treatments but suffered high post-fire mortality from bark beetle attacks. This paper describes the results of four years of post-fire monitoring of ponderosa pine mortality and resin flow in areas subjected to low intensity spring burning (SB), moderate intensity fall burning (FB), or no burning (unburned controls, UC). Crown vigor estimates, correlated with ring width indices, were also included as a factor in mortality and resin flow analyses. Burn treatment was significant in both ponderosa pine mortality and resin flow, as follows: FB > SB > UC. These results suggest that resin defenses overall did not protect trees from post-fire beetle attacks. Crown vigor was positively related to both survival and resin flow. The relationships between burning, tree vigor, and resin defenses in this study suggest a complex web of interactions. Although some physiological mechanisms are still unconfirmed, these findings suggest that beetles may have been attracted to ponderosa pine following burning, perhaps via the release of volatile resin compounds. Following attraction, resin defenses appear to have been important for protecting trees from beetle attacks, with greater defenses in trees with higher crown vigor and higher growth rates. Management recommendations, including a gradual and incremental approach to fire restoration in these stands, are suggested. Source


Vennesland R.G.,Simon Fraser University | Vennesland R.G.,Parks Canada Agency
Canadian Journal of Zoology | Year: 2010

The nesting behaviour of the Great Blue Heron (Ardea herodias L., 1758) was studied in western Canada in 1998 and 1999 to (i) investigate how individual parents assess risk when repeatedly exposed to a disturbance stimulus (an investigator) and (ii) experimentally test in the field whether any variation in their nest defense behaviour was due to experience with the disturbance stimuli or the stage of the nesting period. Heron response declined through the nesting period and the level of response varied among colonies, suggesting different perceptions of risk among groups of herons in the study. It was experimentally shown that variation in the response of herons through one nesting period was due to both behavioural habituation and the stage of the nesting period. Response was stronger in 1999 than in 1998, indicating that habituation did not hold between nesting periods. In general, habituation in herons may bode well for their potential to persist in areas with light human use. But irrespective of habituation, stimuli early in the nesting period and large or novel events may still cause herons to abandon their nests owing to the effects of the stage of the nesting period. Source


Carli C.M.,Parks Canada Agency | Bayley S.E.,University of Alberta
Ecoscience | Year: 2015

Floodplain wetlands in the upper Columbia River valley are governed by the flood pulse. Water flows from the river into adjacent wetlands through channels incised through levees or over the top of the levees. This floodplain is relatively pristine with few road crossings restricting the flow of water in a 110 km length of the floodplain. We describe the floodplain vegetation at three points over 60 years to detect natural vegetation changes and contrast that with changes downstream of roads transecting the wetlands. We mapped eight landscape cover types within 40 floodbasins and four 2 km sections downstream of road crossings at three dates, over 60 years, using historical aerial photographs. Over 60 years the area of open water increased by 77% within the wetlands, and there was a decrease of 14.5%and 40%of marsh and shrub vegetation, respectively. During this time, floodbasins became more connected to the river. We observed greater change within the natural wetlands than in sections downstream of the road crossings. Since floodplain ecosystems are inherently complex due to their highly dynamic nature, isolating specific causes of trends is difficult. However, large-scale loss of vegetation and increase in open water has dramatically changed the wetlands. © 2015 Taylor & Francis. Source

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