Browsing by Author "Reid, Mary"

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    Acoustics of Mountain Pine Beetle and Lodgepole Pine
    (2014-07-21) Kaiser, Mathias; Reid, Mary; Yack, Jayne
    Mountain pine beetles (Dendroctonus ponderosae) produce acoustic signals in a variety of contexts but more study is needed on the function(s) of their signals and on the acoustic cues beetles use. I studied the context-dependent acoustic signalling of male beetles to elucidate the function(s). When stressed, individuals produced short signals, typical of insect anti-predator signals. Prior to mating, individuals produced longer signals that were related to body size with potential implications for mate selection. I further examined the long-proposed idea that beetles could use acoustic emissions from their host, lodgepole pine (Pinus contorta), for host selection. Emission rates recorded in the field increased with presumed water stress and appeared to be related to lower quality trees. I then tested the effects of acoustic emissions on female host choice in a playback experiment and found that isolated females tended to prefer hosts with high acoustic emission rates.
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    Analytical, Dynamic Variable Game Theory Modelling, and Practical Investigations of the Sequential Tactics of Coursing and Tending in Bighorn sheep (Ovis canadensis)
    (2023-12-11) Tate, Ryan Geoffrey; Ruckstuhl, Kathreen; Neuhaus, Peter; Reid, Mary; Oxoby, Robert
    Animals might use different mating tactics to increase their fitness. While some are genetically determined, some are plastic, depending on intrinsic and extrinsic factors. Within the plastic tactics, there can be further temporal structure, in which animals switch tactics once they reach a certain size or competitive ability. This thesis reviews the literature on the terminologies, strategies versus tactics, used in evolutionary game theory, while also making suggestions on improving, standardizing, and clarifying the use of terminology. It then looks at fixed-sequence mating tactics, using an analytical model, to investigate the conditions under which a fixed-sequence tactic can evolve. Then, using a dynamic variable game theory model, the thesis examines various parameters affecting the likelihood of a mating tactic called coursing to involve challenging the dominant male, using another tactic, called tending. Finally, this thesis analyses a long-term data set on bighorn sheep (Ovis canadensis) to see how coursing effort affects coursing and later-in-life tending outcomes.
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    Animal Movement and Distribution at Habitat Edges
    (2015-02-02) Young, Hilary Catherine; Reid, Mary
    The response of organisms to habitat edges is a key factor affecting their distribution across the landscape. Resources are commonly expected to be the primary driver of edge responses, but additional processes may be important. Here I tested resource-based hypotheses and their alternatives by measuring the distribution of organisms and their resources at edges in laboratory and field settings. One non-resource-based process for animal accumulation at edges is a slowing of movement. I recorded the movement paths and distribution of Tribolium confusum beetles in an artificial arena devoid of resources. Beetles took smaller steps with larger turn angles near edges than in the arena’s centre, resulting in a distribution biased towards the edge. The proportion of time spent at edges also depended on the beetles’ propensity to cross the edge. These results suggest that proximate mechanisms such as movement behaviour should be explicitly considered when interpreting animal distributions. To investigate distribution at edges in nature, I examined the response of moose (Alces alces) and deer (Odocoileus hemionus and O. virginianus) to forest-clearcut edges of different ages. Moose responded to differences among habitat types studied but not to distance from edge within habitat types. Clearcuts > 15 years in age contained the most food and cover and were preferred to the adjacent forest and to clearcuts < four years in age. Conversely, differences in deer preferences were detected both among and within habitats. Deer were found more frequently in forest habitats than clearcuts of any age. They were also generally found closer to edges than far from them, although in old clearcuts and the adjacent forests, deer abundance dropped within 50 m of edges. I found evidence for the influence of food and cover availability on deer distribution among habitats, but it was weaker within habitats. These studies suggest that factors other than resources may affect the response of animals to habitat edges, although the field studies were largely consistent with resource tracking. To develop effective models predicting the impact of landscape heterogeneity, researchers should determine both the distribution patterns at habitat edges and the main mechanistic drivers behind these patterns.
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    Ecology of Sex Ratios in Mountain Pine Beetles, Dendroctonus ponderosae
    (2016) Lachowsky, Leanna Elizabeth; Reid, Mary; Gwynne, Darryl; Harder, Lawrence; Vamosi, Steven; Wynne-Edwards, Katherine
    Biased sex ratios pose a fundamental question in evolutionary ecology. Populations are expected to have equal numbers of males and females when each offspring is produced from one mother and one father with equal genetic contributions. In mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins, consistent reports of female-biased adult sex ratios (2:1 F:M) demand explanation. I investigated whether adult sex ratios of MPB reflected initial investment or became biased through adaptive or non-adaptive processes. Differential mortality is a potentially non-adaptive process that could bias sex ratios at later life stages, an idea often invoked to explain female-biased adult sex ratios in this system. However, Fisher noted that if mortality occurs during parental investment, selection will act to bias the primary sex ratio towards the sex with higher mortality, achieving an evolutionary stable state where expenditure to each sex is equal. Individual allocation strategies may differ depending on maternal condition. In insects, daughters were expected to benefit more from increased investment because of the strong relationship between body size and fecundity. Through genotyping of eggs from individual broods reared in the laboratory, I found that primary sex ratios of MPB were male-biased (~1:0.86). Male-biased primary sex ratios were counter to expectations if the sex-ratio distorter Wolbachia was acting in the system; Wolbachia was not detected in a screen of ten populations. Female-biased adult sex ratios arose from subsequent male-biased mortality, observed in both laboratory-reared broods and in experimentally manipulated overwintering field populations. Moreover, condition-dependent allocation occurred, but was counter to expectations, with larger females producing more males than did smaller females. Larger mothers produced larger eggs that experienced less male mortality. In this case, larger mothers gain more from investing in the rare sex than investing in daughters. Given male-biased developmental mortality, a male-biased primary sex ratio is consistent with Fisher’s theory of equal investment favouring the sex with greater mortality during parental investment. Further, differential mortality of the sexes is a strong selective force to which condition-dependent sex allocation may respond more strongly than increases in body size.
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    Effects of Hurricane Maria on the Bat Community on the Caribbean Island of Dominica
    (2022-10-25) Sims, Lisa Marie; Barclay, Robert; Pavelka, Mary; Reid, Mary; Johnson, Steig
    In the Northern tropics, hurricanes can have detrimental effects on bat communities causing direct mortality and injury, and by altering the landscape and disrupting resource availability (i.e., food and roost sites). Islands are particularly vulnerable because they are isolated, closed systems. Therefore, with the predicted increase in frequency of major storms, understanding the response by bats in insular communities is vital. I examined the effects of Hurricane Maria on the bat community in Dominica. Maria was a category 5 storm that struck on 18 September 2017 causing substantial damage across the island. I measured changes in diversity and abundance for the entire bat community, and further examined effects on abundance, body condition and reproductive rate for the four most common species in three foraging guilds – Artibeus jamaicensis (frugivore), Monophyllus plethodon (nectarivore), Molossus molossus and Myotis dominicensis (insectivores). In general, Hurricane Maria had negative effects on the bat community. All guilds were negatively impacted but not all species, and frugivores showed the strongest negative responses. Maria negatively affected all the common species except M. molossus. Reduced abundance for common species, particularly frugivores (e.g., A. jamaicensis) resulted in a more even distribution and greater diversity post-Maria. The largest declines in abundance occurred in the frugivores, which I suggest was primarily due to loss of food and roosts. There was no change in body condition for any guild indicating that individuals that survived were able to obtain enough food. However, there was a significant decline in female reproductive rate for frugivores suggesting a trade-off between energy for survival and reproduction. A comprehensive understanding will require longer-term monitoring post-hurricane.
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    The Effects of the Kenow Wildfire on the Bat Community in Waterton Lakes National Park, Alberta
    (2022-01-27) Low, Erin Blair; Barclay, Robert; Reid, Mary; Summers, Mindi; Bender, Darren
    Fire is one of the most important natural disturbances shaping forest communities. Fire impacts bat communities by changing forest structure, foraging opportunities, and roost availability. I examined the effects of the Kenow wildfire on the bat community in Waterton Lakes National Park (WLNP), Alberta. The Kenow wildfire was a severe fire that burned 38% of the park in September 2017. I radio-tracked female and male Myotis lucifugus to examine roosting behaviour and roost-tree availability two- and three-years post-fire. Reproductive female maternity colonies were found exclusively in buildings in the Waterton townsite. Males and non-reproductive females were tracked to tree and rock roosts in both burned and unburned areas. Roost-tree availability does not appear to have changed immediately after the wildfire. WLNP bat activity was examined using acoustic detectors to record bat echolocation calls at thirteen sites for three years before and three years after the wildfire. I analyzed echolocation recordings to examine bat activity changes pre- and post-fire as well as between burned and unburned areas. The Kenow wildfire negatively affected Eptesicus fuscus/Lasionycteris noctivagans, Lasiurus cinereus, and Myotis evotis. 40 kHz Myotis activity, likely predominately M. lucifugus, did not change pre- to post-fire. However, activity increased in burned areas and decreased in unburned areas. Myotis lucifugus are opportunistic and were likely able to adapt quickly to the changes in foraging habitat, insect communities, and roosting opportunities after the wildfire. Eptesicus fuscus/L. noctivagans, L. cinereus, and M. evotis were likely less adaptable to the significant ecological changes caused by the wildfire. However, the results are for the first three years post-fire and it may take time for the positive effects of the Kenow wildfire to be observed.
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    Floral Anthesis Rate and Pollen Limitation in Delphinium glaucum and their Consequences for Female Fitness
    (2016) Cameron-Inglis, Hazel; Harder, Lawrence; Rogers, Sean; Reid, Mary; Goldblum, David
    Phenological mismatch between plants and their pollinators and/or interspecific competition for pollination can cause insufficient pollen quantity and/or inadequate pollen quality to limit seed production and siring. Inflorescence display size, a dynamic part of pollinator attraction, influences pollinator behaviour and movement. Thus, a rapid increase in display size as plants begin flowering caused by initially rapid flower anthesis should promote recruitment of pollinators to newly flowering individuals and species. Tests of two assumptions of this hypothesis for Delphinium glaucum revealed: 1) declining anthesis rate during a plant’s flowering period is an intrinsic characteristic of inflorescence architecture, rather than a response to internal resource economy; and 2) pollinator limitation early during the flowering period reduced ovule fertilization and elevated autogamous self-mating. These results suggest that rapidly increasing initial display size largely contributed to the quality, rather than the quantity of female mating. Consequences for male outcross success remain to be assessed.
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    Growth, Mortality, and Genetic Structure: Effects of Harvest and Management Strategies on Walleye (Sander vitreus) Populations in Alberta, Canada.
    (2016) Allen, Brandon; Rogers, Sean; Reid, Mary; Spencer, Stephen; Galpern, Paul
    Managed populations exhibit different phenotypic and genetic signatures from their natural counterparts. Walleye (Sander vitreus) are a heavily managed species recovering from population collapse in Alberta, Canada. In my thesis, I examined the effects of harvest on growth, mortality, and genetic structure. First, I used 8200 individuals to test associations between growth curves, lake characteristics and management strategies. Second, I used 17,763 individuals to determine how population mortality rates vary between management strategies. Third, I assessed the genetic population structure for seven populations and differences in genetic variation between the 1970s and 2000s. I found that growth rates were associated with certain lake characteristics, including management strategies, and mortality rates did not vary between strategies. I observed a substantial loss of genetic diversity between the 1970s and 2000s, which supports reports of population collapse. My results illustrate the effects of harvest on phenotypic and genetic diversity in managed populations.
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    Impacts of Sulfur Dioxide Emissions on Lodgepole Pine Growth in Alberta, Canada
    (2021-05-14) Earl, Devon; Reid, Mary; Norman, Ann-Lise; Goldblum, David; Layzell, David
    Stressors to trees could alter the relationships between climate and tree growth or affect tree growth directly. Anthropogenic emissions of sulfur dioxide (SO2) are one such stressor that may complicate predictions of future tree growth. Sulfur dioxide may affect tree growth and climate-growth relationships directly by entering through stomata and altering photosynthetic rate, or indirectly by causing soil acidification. I assessed how the growth and climate-growth relationships of lodgepole pine (Pinus contorta) changed with varying SO2 emissions intensity and distance from the source in two areas of Alberta, Canada with sour gas facilities. To assess whether SO2 altered tree response to climate, I determined the monthly climate variables (temperature and precipitation) that were important to growth and then assessed how the growth response of trees to these variables changed between periods of differing emissions and proximity to the source of emissions. Overall, climate had a stronger effect on tree growth in the high SO2 emissions period compared to the periods of no emissions and reduced emissions, and farther from the source of emissions compared to near. Liming in stands near the source of emissions likely reduced the effects of SO2 on tree growth and climate-growth relationships in one area. In the case of previous year late summer precipitation, the commonly observed positive effect on tree growth was reversed only during the high emissions period, near the source of emissions. This could indicate that under heavy acidic deposition, increased precipitation may lead to soil nutrient leaching. After accounting for climate, I found that the effect of SO2 emissions on tree growth was complex. In one study area, tree growth near the source of emissions was more strongly negatively affected by 6-year and 10-year cumulative emissions than by annual emissions, indicating that soil acidification may be more important to tree growth than direct effects of SO2 on photosynthesis. SO2 and other stressors to trees should be considered to develop sustainable forestry management practices in the context of a changing climate and in the development of natural climate change mitigation strategies.
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    Lodgepole Pine and Interior Spruce Radial Growth Response to Climate and Topography in the Southern Rocky Mountains, Alberta
    (2018-01-12) Ackerman, Frances; Goldblum, David; Jasechko, Scott; Reid, Mary
    As climate change continues to alter forest ecosystems, it is important to understand the details of how trees respond to climatic conditions across the landscape. Climate change may have spatially variable impacts on radial growth of tree species growing in mountainous environments, making generalizing across broad spatial scales inappropriate from a forest management perspective. In Alberta, understanding the growth response of lodgepole pine (Pinus contorta) and interior spruce (Picea glauca x Picea engelmannii hybrid) to climate and topographic variables will assist in understanding how these species may be affected by future changes in climate. Radial growth-climate response of trees in mountainous landscapes (e.g. the Rocky Mountains) may be altered at fine scales by topography and are often unstable through time (i.e. ‘divergence problem’). Because of this, it is important to consider topographic variables when spatially and temporally analyzing tree radial growth response to climate in subalpine communities. Currently, there is knowledge of how trees respond to climate at regional scales, but less is known about how trees interact with climate and topography at the catchment scale. This thesis addresses these topo-climatic relationships in the front range of the Rocky Mountains, Alberta, with particular focus on lodgepole pine and interior spruce growth response to monthly climate (total monthly precipitation and average monthly temperatures), aspect, slope, elevation, soil depth, and topographic wetness index (TWI). Results suggest species-specific and site-specific spatiotemporally diverse radial growth responses to climate and topography, indicating that future climate change is likely to have highly spatially variable impacts on tree radial growth response in mountainous environments. Keywords: lodgepole pine (Pinus contorta), interior spruce (Picea glauca; Picea engelmannii), dendroclimatology, topography, climate change, biogeography
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    Mathematics Content Knowledge, Mathematics Teacher Efficacy, and Pedagogy
    (2013-12-13) Reid, Mary; Scott, Shelleyann; Scott, Donald
    An important goal in elementary mathematics classrooms is for teachers to employ instructional practices that engage students to develop sustainable and deep conceptual mathematics understanding. In preservice education, this often requires transforming student teachers’ beliefs about teaching mathematics, and their knowledge of mathematics content and pedagogy. This study involved preservice teachers from two mathematics methods courses and specifically examined teaching and learning experiences that contributed to their development in: 1) content knowledge, 2) teacher efficacy, and 3) pedagogy. Building capacity across these three constructs was considered significant in the preservice mathematics courses. This research focused on identifying the factors which influenced students’ development in these three constructs with the view to enhance preservice mathematics programs. The theoretical framework for this research was underpinned by several theories: mathematical knowledge for teaching theory, self-efficacy theory, constructivist learning theory, and adult learning theory. These selected theories were deemed to be highly pertinent to the phenomena of preservice mathematics teacher development and drew upon a range of theorists such as: Ball, Thames, and Phelps, 2008; Bandura, 1986; Dewey, 1938; Knowles, 1984; Mezirow, 1991; Piaget, 1952; and Vygotsky, 1978. Through a mixed methods approach, this study utilized quantitative data related to student teachers’ mathematics content knowledge, teacher efficacy, and anxiety. The qualitative data included student teachers’ journals, interviews, and the researcher-instructor’s journals. The five broad themes that emerged from the converged data were: 1) importance of the instructor’s role in mathematics teacher development; 2) problem solving to support conceptual understanding; 3) building confidence as a mathematics teacher; 4) working towards constructivist pedagogy; and 5) classroom management. Two models were developed from the findings in this study. Model one highlights the differentiating mathematics needs of preservice teachers and ways to support their needs prior to the start of their teacher education program; and model two addresses conceptualizations of coherence and how this can be achieved across the dimensions of mathematics preservice education. These models and this study’s significant findings will be of interest to those seeking to enhance preservice elementary mathematics teacher education through building coherence and implementing strategies to meet the varying backgrounds of student teachers.
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    Plasticity of Reproductive Traits in Response to Pollen-Limited Fruit Initiation in an Annual Plant
    (2023-09-26) Mount, Nathaniel James Hamnett; Harder, Lawrence; Rogers, Sean; Reid, Mary; Samuel, Marcus
    Pollination is a highly uncertain and variable process, and insufficient pollination commonly limits seed production and siring success by flowering plants. Due to this unpredictability, plants, particularly those with annual or otherwise semelparous life-histories, could benefit from phenotypic plasticity in their reproductive growth and function that enhances the overall likelihood of pollination and provides some compensation for pollen limitation. To test this hypothesis, three hand-pollination experiments were conducted using a rapid-cycling variety of Brassica rapa to determine whether limited pollination stimulated plastic responses that could increase seed production relative to the fecundity that would be realized in the absence of plasticity. Plants on which a limited fraction of flowers had been pollinated exhibited many differences from well-pollinated plants. Compared to well-pollinated plants, pollination of 25% of a plant’s flowers reduced fruit production, indicating pollen limitation. In contrast, fruit number did not vary with pollination if at least 50% of flowers were pollinated, indicating resource limitation. In response to pollen limitation, poorly pollinated plants produced more flowers than well-pollinated plants, which should increase their overall pollination success. Neither pollen number per flower on terminal racemes nor its siring ability varied with pollination success. However, plants with few developing fruits produced more ovules in distal flowers of their axillary racemes and more seeds per distal fruit on all racemes compared to plants with many developing fruits. Pollen-limited plants with relatively few seeds overall produced larger seeds, which should enhance seed germination and seedling establishment. Overall, pollen-limited plants also opened fewer flowers per day, extending their total flowering period and exposure to pollinators. Nevertheless, pollen-limited plants opened more flowers per day during late flowering, which increased the number of flowers displayed simultaneously and should enhance pollinator attraction. These results indicate that, rather than being helpless against pollen limitation, plasticity of reproductive characteristics allows annual plants to compensate, at least partially, for low per-flower pollination probability.
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    Roosting Behaviour and Thermoregulation of the Northern Long-Eared Bat (Myotis septentrionalis) Near the Northern Extent of its Range
    (2016) Kaupas, Laura; Barclay, Robert; Reid, Mary; Vamosi, Steven; Melin, Amanda
    Reproductive female mammals have high energetic demands. This may be particularly true for small, nocturnal mammals at high latitudes, where temperatures are relatively low and summer nights are short. Tree roosts are colder than building roosts, likely resulting in greater energetic constraints for tree-roosting bats. My research goal was to determine how reproductive, tree-roosting Myotis septentrionalis reduce the costs of roosting in relatively cool roosts near the northern extent of their range. I investigated the roosting behaviour of M. septentrionalis, and the thermoregulatory patterns and reproductive timing of M. septentrionalis and building-roosting M. lucifugus in the Northwest Territories, Canada. Myotis septentrionalis exhibited roosting behaviours that should reduce energetic costs. Despite lower tree-roost temperatures, the two species used similar thermoregulatory patterns, suggesting higher energetic costs for M. septentrionalis. However, M. septentrionalis foraged for longer, perhaps compensating for these higher costs, resulting in similar reproductive timing and rates between species.
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    Spatial Synchrony of Predator-Prey Dynamics in Response to Cyclic Temperature Fluctuations
    (2021-09-21) Osterlund, Kaitlin Breanne; Fox, Jeremy; Reid, Mary; Galpern, Paul
    Spatial synchrony in populations occurs for many species, but is most apparent for species with populations that experience cyclic fluctuations. Population cycles can enhance the strength of synchrony-producing mechanisms by phase-locking cycles through dispersal events, or by entraining cycles to local cyclic environmental perturbations. Comparative evidence shows that density-dependent population regulation can differ spatially based on local environmental fluctuations that drive synchrony, but there is a lack of empirical evidence to further support this mechanism. This study looked to determine whether population cycles and cyclic environmental fluctuations impact the occurrence and persistence of spatial synchrony. A literature review was conducted that supported the relation between spatial synchrony and population cycles. A Rosenzweig-MacArthur model with oscillating density dependence was produced to establish expected results for empirical tests. Patches of microcosm jars were then cycled between different temperatures to create environmental perturbations on model protist species Tetrahymena pyriformis and Euplotes patella which generate predator-prey cycles. The population cycles were manipulated by varying media enrichment and temperature cycle period length to establish a threshold synchrony range. Model results show that spatial synchrony occurs at high amplitude cyclic environmental fluctuations with cycle periods that closely match to the cycle period of the populations that are being synchronized. Due to COVID-19 restrictions, the experiment could not be carried out as initially intended, and results reflect the limitations imposed. Results suggested by the model could not be replicated experimentally. Future directions are suggested for studies with no pandemic-related restrictions.
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    Thermal remote sensing of mountain pine beetle green attack
    (2022-03) Mckeeman, Taylor; McDermid, Greg; Castilla, Guillermo; Reid, Mary
    Mountain pine beetle (Dendroctonus ponderosae Hopkins, MPB) has caused extensive damage in the forests of western North America. There has been little success in identifying affected trees at the green-attack stage via remote sensing: a goal that would greatly support targeted management efforts to reduce the spread during times of epidemic populations. High-resolution thermal remote sensing has yet to be tested for this application. In this thesis I describe the theoretical foundations that explain why the measurement of thermal radiance is a justified approach to green-attack detection. I then develop experiments in a greenhouse and in forest stands of lodgepole pine to simulate MPB attack and to test my two proposed hypotheses: the warm-tree effect and the cool-tree effect. In the greenhouse, completely green and healthy-looking geraniums showed statistically significant warming trends after 10 hours of droughting compared to watered subjects, revealing an estimated difference of 1.5 degrees Celsius in minimum canopy temperature and support for the warm-tree effect. The cool-tree effect (not observed in the greenhouse) was detected in one of my field sites, but a review of the data revealed suspicious patterns which led to an indeterminate conclusion regarding its validity. Patterns of the warm tree effect were visible in my second field site early on, but then seemed to vanish as the experiment progressed. I speculated that the 10- to 20-year drought that began during my study period explains my observations most appropriately, though explorative modelling of its impacts showed low relative predictive power. I subsequently concluded that the validity of the warm-tree effect, though promising, was also indeterminant and that it requires further investigation. This work should be applied in further research to validate the warm-tree effect in actual MPB green-attack trees. These efforts should consider using the minimum or 5th percentile canopy measurements (found to be the strongest metric) and controlling for the potential impacts from incoming solar radiation and the distance from tree to sensor.
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    Transitions in Boreal Wetland Macroinvertebrate Community Composition Across a Natural Salinity Gradient
    (2022-06) Vercruysse, Brenten; Ciborowski, Jan; Jackson, Leland; Reid, Mary; Wytrykush, Carla
    Nearly 65% of Alberta’s northern boreal landscape is comprised of wetlands (primarily peatlands), which are lost in the process of open pit mining for oil sands. Demonstration wetlands recently created in reclaimed postmining watersheds are productive and support diverse biota. However, their water tends to be sodic due to the presence of salts in the soils used in their construction and residual sodium from the bitumen extraction process. Saline wetland systems occur in northern Alberta in areas where deep aquifer upwellings contribute significantly to a wetland’s water budget. I sampled the water chemistry and aquatic invertebrates in a suite of 52 pools ranging in specific conductance from 3,757 to 20,170 S/cm in a patterned fen southeast of Fort McMurray, Alberta, to identify patterns of community composition along the salinity gradient. Sodium, chloride, magnesium, and calcium were the dominant ions present in the saline fen. Pools with relatively low salinity supported abundant densities of gastropods and odonates whereas the most saline pools were dominated by Diptera larvae, especially genera of mosquitos. Threshold Indicator Taxon Analysis (TITAN) identified a set of 11 sensitive and 9 tolerant taxa diagnostic of specific conductivity. Community composition changed markedly at a threshold of 6,335-9,385 S/cm, equivalent to chloride concentrations of 1,579- 2,535mg/L. These findings may provide a useful frame of reference for anticipating community composition in wetlands forming in sodic areas of the reclaimed postmining landscape of the AOS.
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    White spruce (Picea glauca) traits affecting the success of spruce beetles (Dendroctonus rufipennis) in the southwest Yukon
    (2017) Goulding, Megan; Reid, Mary; Barclay, Robert; Johnson, Edward; Goldblum, David
    A major outbreak of spruce beetle (Dendroctonus rufipennis) occurred in the southwest Yukon between 1990 and 2007. I determined how white spruce (Picea glauca) allocation to growth, defence and reproduction affected spruce beetle population growth, and how climate mediated these interactions. Spruce beetle population growth was greatest in years when spruce grew more slowly and had fewer cones, with no detectable effect of mean summer or winter temperature. For individual spruce trees, the probability of being attacked by spruce beetles increased with decreasing relative growth rates, increasing tree diameter, and increasing number of resin ducts produced in the previous five years; cone production did not affect attack probability. Once attacked, the probability of tree death increased with both decreasing relative growth rate and number of induced resin ducts produced in the attack year. These results show that tree growth and defence but not reproduction determined spruce beetle susceptibility.