The Ontario of Ministry Natural Resources spends considerable effort each year managing white-tailed deer (Odocoileus virginianus ). A selective harvest system, which regulates kill by issuing a restricted number of either-sex harvest permits (called tags), has been the main tool employed to manage populations. Using harvest and biological data from 1980 to 1997, we reviewed the historical ability to regulate both harvest and population size in Ontario, and assessed our ability to predict future population size. Under the selective harvest system, when more than 40% of hunters hold tags, kill can only be significantly increased by increasing hunter numbers and even below 40% tags, the most effective regulation of kill involves regulating both the number of tags and the number of hunters. The ability to regulate harvest may also be limited by hunter behaviour. Deer population size, as indicated by deer seen controlling for effort, was mainly regulated by density-dependence, with limited effects from summer and winter weather conditions. Harvest exhibited no effect on population size, except in a few, select areas where relatively large kills produced limited down-regulation. The best model created to predict changes in population, for management purposes, had poor predictive ability and barely outperformed randomly choosing a number. These results indicate an inability to regulate deer populations through a sport harvest. Kill, at historical levels, does not appear to regulate population density. Further, based on currently collected data, we are unable to make accurate predictions of future population size on which to base management decisions. We suggest a new management system, in recognition of the limited predictive and management ability, in which management actions are untaken only when estimated populations exceed broad limits.

This thesis examines the accumulation of persistent organochlorine compounds in Canadian mountain environments through the sampling of air and coniferous vegetation along a 1430-meter elevation gradient in the Canadian Rocky Mountains. Results showed that lower temperatures encountered in high altitudes favor the accumulation of chemicals with higher volatility in vegetation. Air concentrations further suggest that the reason for this accumulation in elevated areas is increased atmospheric deposition from distant sources and not from temperature-induced revolatilization from local terrestrial surfaces. Seasonal decreases in plant concentrations indicate evaporative processes, and volatilization from vegetation was confirmed by calculated fugacity gradients. However, volatilization contributes very little to air concentrations and the subsequent fractionation upslope, which appears to be dominated by long-range transport. Multivariate analysis revealed that, in addition to cooler temperatures, other environmental conditions common to mountain ecosystems, such as elevated precipitation and lower pressure, promote chemical deposition onto vegetation.

Dendrochronological techniques were used to study white spruce ( Picea glauca [Moech] Voss) dynamics in the altitudinal forest-tundra ecotone in the southwest Yukon Territory. At two sampling sites, all Picea glauca individuals within 9 delineated quadrats in the forest-tundra and forest were sampled to estimate dates of establishment and growth variations using tree-ring chronologies. Regeneration in the forest-tundra ecotone was low from the late 1800s to the mid-1900s, however has increased since the 1920s. Recent peak periods of establishment parallel increased radial growth trends, which may have resulted from the long-term warming trend of the 20 th century. Seedling proximity to pre-established individuals in the forest-tundra ecotone suggests regeneration from a local seed source. Growth in height of pre-established krummholz individuals accelerated around the 1950s. Tree establishment in the forest-tundra and forest appear to be influenced by summer temperatures of the current growing season, and a high degree of similarity in tree growth at different sites in the southwest Yukon suggests a regional response to a large-climate signal. An increase in krummholz height and improved seedling establishment in the forest-tundra ecotone could result in a shift from krummholz to symmetrical trees and/or from patch forest to continuous forest.

In 1999 and 2000 reproductive success and chemical biomarkers were measured in 16 day old tree swallows (Tachycineta bicolor) collected from nine sites along the St. Lawrence River in Canada and USA. Chicks were collected for analysis of organochlorine pesticides, polychlorinated biphenyls (PCBs), total mercury, polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), and measures of corticosterone response, and vitamin A concentrations. Study sites were located in the vicinity of landfill sites and industrial outfalls in the St. Lawrence River area of concern (AOC). Altered vitamin A metabolism and corticosterone homeostasis in wildlife exposed to contaminants may lead to numerous effects on reproduction, growth, and immune function. Overall these data suggest that current levels of organochlorine contamination may be affecting the hypothalamo-pituitary-adrenal axis and vitamin A levels in environmentally exposed tree swallow nestlings along the St. Lawrence River. (Abstract shortened by UMI.)

Patterns of foraging behaviour of Thick-billed Murres (Uria lomvia ) feeding nestlings at Coats Island, Nunavut in northern Hudson Bay were studied. Small, electronic data recorders attached to adult birds were used to quantify dive behaviour and flight activity while provisioning for nestlings. Observations of individuals returning to the colony were conducted to identify the types and sizes of prey items birds were delivering to chicks. Trends in species composition of nestling diets were examined from 1994 to 2000. Information obtained on foraging behaviour are discussed in relation to general predictions of central place foraging theory, as well as in relation to the ecology of prey species in the vicinity of the colony. The implications of my results for the value of information gathered from seabirds, as indicators of their local marine environments, is addressed. (Abstract shortened by UMI.)

Picocyanobacteria (PC) are microscopic blue green algae responsible for a tenth of the total primary production of marine and freshwater systems. In this research, the ecology of temperate lake PC populations and their flow cytometry signatures were studied. In the first chapter, I examined the relative importance of growth versus losses of picocyanobacteria (PC) and the influence of physical and chemical variables on their in situ abundance in 48 temperate freshwater lakes. Growth and loss rates of PC were estimated from in situ incubations using a selective metabolic inhibitor technique and abundance of PC was determined by epifluorescence microscopy. In the second chapter, I examined the use of flow cytometry to identify PC and determine their abundance in lake water samples. The background noise appears higher in lake samples than marine ones. The source of this noise needs to be identified and corrected in future studies. However, flow cytometry is a promising tool for examining pigment distributions and for rapid assessments of the phytoplanktonic community. Epifluorescence remains the most reliable technique to determine PC abundance and pigment composition in freshwater lakes. (Abstract shortened by UMI.)

Like many rivers around the world, the Rideau River is under pressure from a number of human induced activities resulting in a loss of species and habitat. In order to prioritise conservation efforts, it is necessary to understand what type of habitats will support the widest range of species. This study examines which physical and chemical factors exert the strongest influence on the diversity and community composition of aquatic macrophytes in the Rideau River. Macrophyte species were surveyed at 33 sites on the Rideau River, Ontario, in six 1 m2 quadrats aligned in a belt transect perpendicular to shore along a depth gradient of 0.5 m to 2.0 m. Regression analysis showed species richness and Shannon diversity were significantly related to water velocity, transect length, slope, and organic content. Multiple regression provided a model whereby 70% of species richness was explained by organic content, transect length, water velocity and chlorophyll a, and 77% of Shannon diversity was explained by organic content and water velocity. Mantel tests showed only chlorophyll a was weakly correlated with species composition. Canonical correlation analysis showed floating and floating-leaved species to favour habitats with low water velocity. No other significant patterns were found. It appears that while species diversity can be predicted from physical environmental variables, species composition cannot.

This study investigates the succession following fire in a relatively dry area of the boreal forest, the Shakwak Trench, southwest Yukon. The postfire successional regime is determined by an analysis of age structure and composition of tree populations in stands of different ages. The dendroecological approach used in this study is based on the sampling of one plot in each of 11 fires ranging from A.D. 1844--1998. Picea glauca established 0--4 years after fire and reached a period of maximum establishment after 20--40 years. Populus tremuloides was generally recruited immediately after fire and was no longer present after approximately 20 years, at which point, the Picea glauca began to dominate. Salix spp. were found in all stages of succession, but decreased in abundance through time. Five chronologies that were developed from ring-width measurements of the older Picea glauca trees depict similar growth-ring patterns, suggesting a large-scale climate influence on all sites in the region. There is a weak relation between the variability of the tree-ring chronology and the establishment of Picea glauca seedlings. Regeneration of tree species after fire is primarily driven by biological influences rather than climatological ones.

The present study aimed to determine the effect of arbuscular mycorrhizal (AM) symbiosis on plant nitrogen (N) nutrition. Previous studies had shown, mainly from soil experiments, the ability of AM fungi in their N uptake and transfer to host plants. These results led us to postulate that AM fungi contribute to enhance the activity of N-assimilating enzymes in host roots, and possess their own N-metabolic system. To investigate this, N key-enzyme activities were examined in Ri T-DNA carrot (Daucus carota L.) roots, grown into an in vitro system, with or without the AM fungus, Glomus intraradices Schenck & Smith. Such a system allowed us to grow and maintain an experimental model of intact roots-AM fungus, in a controlled and pathogen-free environment. Total carbon (C) and N contents had been quantified by Elemental Analysis in AM and non-AM roots and in the mycelium. By Mass Spectrometry, the uptake and transfer of labelled nitrogen (15N) from the fungal mycelium to AM roots, as well as in the non-AM roots, were also determined. Finally, some of the N-assimilating enzymes were characterized by immunodetection (Western blot). (Abstract shortened by UMI.)

Over the last 150 years the 'natural' landscape in southeastern Ontario (as in much of the world) has undergone a dramatic transformation due, in large part, to widespread deforestation, wetland destruction and degradation, and increased agricultural activity. The negative impacts of such land-use modifications may include declines in wetland water quality and biodiversity. Here, I develop models to predict the effects of adjacent land-use on wetland water quality, and amphibian and plant diversity using indices of land-use intensity such as, forest cover, road density, building density, fertiliser application, livestock density etc. I find negative relationships between land-use intensity and wetland water quality, and amphibian and plant species richness. The strongest relationships tend to be with forest cover, however, other important variables include wetland size, road density, and the proportion of adjacent lands that is wetland. Moreover, there are complex interactions among variables. For instance, part of the effect of forest cover on plant and amphibian species richness may be indirect, through effects on wetland water quality but there are also effects of forest cover on both plants and amphibians that are independent of wetland water quality. In a conservation context, one important question is 'what is the scale of adjacent land-use effects?' I find that landscape modifications up to 2000--4000 meters from a wetland edge have the strongest correlations with wetland water quality and amphibian species richness while, land-uses 250--400 meters from the wetland edge are most strongly correlated with plant species richness. The conservation implication is that the current Ontario Wetland Policy which (1) evaluates and protects wetlands on a site-by-site basis and, (2) regulates adjacent land-use out to 120 meters from the wetland edge, is not likely to ensure long-term protection of wetland water quality and biodiversity in Ontario.