In-situ net community production (NCP) was measured on nine cruises along Line P in the subarctic Northeast Pacific during 2007-2009 and incubation based new, regenerated and carbon production on four cruises starting in August 2008. In-situ NCP, determined using the O2/Ar gas ratio in the mixed layer, averaged 18.4±5.1 mmol O2 m-2 d-1 for stations west of 130°W in June and August. In-situ NCP was nearly equivalent to 24-h 15NO3 - based euphotic zone integrated new production (New-P) with an average NCP: New-P ratio of 1.3±0.4 that was consistent over a range of environmental conditions. The relationship between NCP and 24-h 13C integrated production (C-PP) was variable, but with a consistent mean NCP:C-PP ratio of 0.42±0.27 even when historical measurements were included in the comparison. Two offshore high productivity events were observed in the HNLC region of Line P, one centered between 134°W and 139°W and the other west of 130°W. Only one high productivity event shows conclusive evidence of being caused by iron deposition. / Graduate / 0416

<p> Energy balance components were measured over a coastal subarctic wetland in northwestern James Bay during the growing season. The Penman-Monteith combination model was used to determine surface and atmospheric controls on evaporation. The Priestley-Taylor combination model was used to calculate an evaporability parameter, a. Combining these two models resulted in determining the sensitivity of a to surface and atmospheric controls. </p> <p> Canopy, aerodynamic, and climatological resistances were influenced by onshore or offshore wind directions. Canopy resistance was dominant and showed a strong seasonal trend a averaged 0.78 and was influenced by wind direction a is most sensitive to canopy resistance, followed by vapour pressure deficit, net available energy, and aerodynamic resistance. </p> / Thesis / Bachelor of Arts (BA)

Climate change is expected to have a strong impact on subarctic ecosystems. Increased temperatures as well as altered precipitation and snow cover patterns are predicted to change species distribution and affect biogeochemical processes in the subarctic tundra. Bryophytes are an essential vegetational component in northern ecosystems, due to their high abundance and importance in many ecological processes. In this study the effects of elevation and altered snow cover on the temporal dynamics of freezing damage in three subarctic bryophyte species (Hylocomium splendens, Ptilidium ciliare, and Sphagnum fuscum) were studied in a snow manipulation field experiment in Abisko, during early spring. Soil temperature and field moisture of moss shoots were collected. A freeze-thaw incubation experiment was conducted to investigate the freeze-thaw cycle resistance of H. splendens and P. ciliare originating from habitats with two differing snow-cover thicknesses. Freezing damage differed significantly between the bryophytes species with P. ciliare experiencing the least and S. fuscum the highest damage. Damage was higher at the low elevation, possibly attributable to acclimation effects. Snow removal led to higher damage in moss shoots, but no interactions of the different snow cover treatments with elevation, species or time were found. Freezing damage increased over time and no recovery occurred, likely due to temporal patterns in soil freeze-thaw cycles during early spring. Soil freeze-thaw cycles were the main factor influencing damage in bryophytes after snow melt. Measured environmental parameters could not explain the entire variation in damage. Damage might additionally be attributable to increased UV radiation or disturbances by herbivores.

The intra-basin variability of snowmelt and meltwater runoff hydrology in an 8 km2 subarctic alpine tundra catchment was examined for the 2003 melt period. The catchment, Granger Creek, is within the Wolf Creek Research Basin, Yukon which is typical of mountain subarctic landscapes in north-western Canada. The study catchment was segmented into nine internally uniform zones termed Landscape Units (LUs) based on their similar hydrological, physiographic, vegetation and soil properties. Snow accumulation exhibited significant variability among the LUs, with greatest snow water equivalent in areas of tall shrub vegetation. Melt began first on southerly exposures and at lower elevations, yet average melt rates for the study period varied little among LUs with the exception of those with strong aspects. In LUs with capping organic soils, meltwater first infiltrated this surface horizon, satisfying its storage capacity and then percolated into the frozen mineral substrate. Infiltration and percolation into frozen mineral soils was restricted where melt occurred rapidly and organic soils were thin; in this case meltwater delivery rates exceeded the frozen mineral soil infiltration rate, resulting in high runoff rates. In contrast, where there were slower meltrates and thick organic soils, infiltration was unlimited and runoff was suppressed. The snow water equivalent had a large impact on runoff generation as soil storage capacity was quickly surpassed in areas of deep snow, diverting the bulk of meltwater laterally to the drainage network. A spatially distributed water balance indicated that snowmelt freshet was primarily controlled by areas with tall shrub vegetation that accumulate large quantities of snow and by alpine areas with no capping organic soils. The intra-basin water balance variability has important implications for modeling freshet in hydrological models.

The arctic and subarctic regions of Canada are increasingly developing as integral, participating parts of the total Canadian and world scene. Basic to this development in the North are the human, natural physical, and designed or man- made environments. This study is concerned with one aspect of the designed environment: human settlements. On the basis of an evaluation of the existing settlement planning situation, an attempt is made to develop a skeletal, yet consistent, theory and methodology for settlement planning in the Mackenzie River Delta, Northwest Territories. The approach is from a comprehensive point of view, and includes social, economic and physical criteria directly in the planning process. A combined systems-factor analysis technique is experimentally developed as an aid to creativity in the planning process. Preliminary results indicate both an immediate practical use and a good potential for the further development of the approach as a panning tool.

The arctic and subarctic regions of Canada are increasingly developing as integral, participating parts of the total Canadian and world scene. Basic to this development in the North are the human, natural physical, and designed or man- made environments. This study is concerned with one aspect of the designed environment: human settlements. On the basis of an evaluation of the existing settlement planning situation, an attempt is made to develop a skeletal, yet consistent, theory and methodology for settlement planning in the Mackenzie River Delta, Northwest Territories. The approach is from a comprehensive point of view, and includes social, economic and physical criteria directly in the planning process. A combined systems-factor analysis technique is experimentally developed as an aid to creativity in the planning process. Preliminary results indicate both an immediate practical use and a good potential for the further development of the approach as a panning tool.

The intra-basin variability of snowmelt and meltwater runoff hydrology in an 8 km2 subarctic alpine tundra catchment was examined for the 2003 melt period. The catchment, Granger Creek, is within the Wolf Creek Research Basin, Yukon which is typical of mountain subarctic landscapes in north-western Canada. The study catchment was segmented into nine internally uniform zones termed Landscape Units (LUs) based on their similar hydrological, physiographic, vegetation and soil properties. Snow accumulation exhibited significant variability among the LUs, with greatest snow water equivalent in areas of tall shrub vegetation. Melt began first on southerly exposures and at lower elevations, yet average melt rates for the study period varied little among LUs with the exception of those with strong aspects. In LUs with capping organic soils, meltwater first infiltrated this surface horizon, satisfying its storage capacity and then percolated into the frozen mineral substrate. Infiltration and percolation into frozen mineral soils was restricted where melt occurred rapidly and organic soils were thin; in this case meltwater delivery rates exceeded the frozen mineral soil infiltration rate, resulting in high runoff rates. In contrast, where there were slower meltrates and thick organic soils, infiltration was unlimited and runoff was suppressed. The snow water equivalent had a large impact on runoff generation as soil storage capacity was quickly surpassed in areas of deep snow, diverting the bulk of meltwater laterally to the drainage network. A spatially distributed water balance indicated that snowmelt freshet was primarily controlled by areas with tall shrub vegetation that accumulate large quantities of snow and by alpine areas with no capping organic soils. The intra-basin water balance variability has important implications for modeling freshet in hydrological models.

Despite their difference in body size and morphology, the moose (Alces alces) andthe mountain hare (Lepus timidus) sustain themselves during winter on similar plantspecies and plant parts in in subarctic environments, namely apical twigs ofmountain birch (Betula pubescens ssp. czerepanovii). Herbivores must select areas anditems of food that provide sufficient intake rates and food nutritional quality whilebalancing this against their intake of dietary fiber and potentially detrimental plantsecondary metabolites. This selection takes place simultaneously at multiple spatialscales, from individual plants and plant parts to patches of food and parts of the wider landscape. While the herbivores must consider their need for food to sustaindaily activities, for body growth and reproduction it is also necessary to avoid predators and harsh environmental conditions. For managers, an understanding of key factors for animal foraging distributions is pivotal to reach intended goals ofmanagement and conservation plans. Knowledge in this area is also important formodels to make accurate predictions of foraging responses of herbivores to resource distributions. The mountain birch forest displays a naturally heterogeneous distribution of trees and shrubs which presents herbivores with a challenge to findgood feeding areas. In an investigation of the spatial distribution of moose browsing on birch and willows (Salix spp.) in two winter seasons separated in time by 14 years,it was found that moose browsing patterns in 1996 were correlated to those observed in 2010. It was also found that moose browsing was spatially clustered within the same distances (1000-2500 m) as densities of willow and birch, but at other spatial scales, browsing was mostly randomly distributed. It was concluded that foragedensity is a cue for moose but only at certain spatial scales. Similarly, a comparison of foraging distribution by hare and moose showed that high birch density was a key factor for both species. In spite of this, hares and moose used different parts ofthe same environment because they respond to food resource distribution at different spatial scales. Hares fed from smaller plants, and focused their foraging activity on smaller spatial scales than moose. These results emphasize the importance of taking into account the distribution of food resources at spatial scales relevant for each species in plans for conservation and management. In an experimental study it was found that intensified browsing on natural forage by mountain hares can be induced locally through placement of food. The induced browsing varied with the amount and quality of the added food, but also with thedensity of natural food plants and natural foraging distribution by hares. Finally, ina last experiment habitat preference of mountain hares across edges between open and forested areas was studied. The results were not consistent; hares utilized baitto a greater extent within forested areas than bait placed on a nearby lake ice, butbait on mires and heaths was either preferred over bait in nearby forest, or utilizedto a similar extent. A possible explanation is that hares have knowledge of their environment such that both forested areas and subarctic mires and heaths are partof its natural home range, whilst the extreme environment on the lake ice is not. During recent decades arctic areas have had an increase in vegetation density andwill be affected by future climate warming and therefore, factors that determineforaging ecology of key herbivores need to be identified. This thesis sheds some light on these factors in relation to spatial scale and forage distribution for two high profile herbivores in the subarctic.

Human demographic changes in association to environmental fluctuations were studied for the North American Arctic and boreal region. Using the frequency of archaeological radiocarbon dates from the Canadian Archaeological Radiocarbon Database as a proxy for population size, past changes in population density were estimated and quantitatively examined in relation to reconstructions of temperature and sea ice conditions. This was conducted across three spatial scales: the entire area, the four major cultural-environmental regions and sixteen subregions in order to identify both broad-scale and local phenomena. There was a high correspondence between millennial and centennial-scale climate variability and paleodemographic changes across the region, with increasing population density during warmer periods and lower density during cooling episodes. An abrupt Late Holocene cooling (neoglaciation) beginning at 3.9 ka triggered a nearly-synchronous population decline across the region. Cooling temperatures and increased sea ice coverage also influenced large-scale migration patterns of Paleo-Inuit peoples as well as their cultural evolution.

Unprecedented rates of anthropogenic environmental change have resulted in dramatic decreases in biodiversity worldwide. In order to persist during changes in both the abiotic and biotic environment resulting from anthropogenic stressors such as climate change and habitat degradation, populations must be able to respond or face extirpation. Predicted population-level responses to environmental change include i) range shifts as individuals disperse into more suitable regions, ii) phenotypic plasticity allowing for shifts in the mean phenotype of the population or iii) microevolution resulting from a genetic change within the population. The goal of this thesis is to assess how species within a community respond to a dramatic change in the environment. This study used the sediment record of a Subarctic pond to investigate the impacts of a rapid increase in salinity on two species of the crustacean zooplankton Daphnia. One species, Daphnia tenebrosa, was unable to persist in the high salinity conditions and is believed to have been extirpated from the system. The other species, Daphnia magna, was tolerant of the new environmental conditions and was present throughout the sediment record. To investigate the changes in life history of D. magna, resting eggs from the sediment were hatched to compare iso-female lines from pre- and post-disturbance time periods. No differences were observed between the clone lines, suggesting that phenotypic plasticity allowed D. magna to persist despite the rapidly changing environmental conditions, and that microevolution in salinity tolerance may not have occurred in this population. This study suggests that, in environments with moderate levels of post environmental change, pre-existing phenotypic plasticity may play a greater role than microevolution in species response to environmental changes. However, not all species from a community display the same response to environmental changes, as seen in this study with the extirpation of D. tenebrosa. To better understand how communities will be affected by future environmental change, further investigations need to be made on what factors influence species response. Identifying species response may allow conservation efforts to focus on species that are unlikely to adapt to environmental change, and are most at risk. / Thesis (Master, Biology) -- Queen's University, 2013-09-29 21:54:34.881