Forest encroachment has been documented across North America, from British Columbia to New Mexico, and is a growing concern due to loss of essential grassland habitat. Climate change, fire suppression, changes in grazing regimes, and differences in microclimate between topographic gradients are the main factors associated with forest encroachment into grasslands. Small-scale factors, such as competition and facilitation also play an important role in forest-grassland dynamics. I examined forest-grassland dynamics in southwest Yukon through dendroecological techniques and repeat image analysis. Dendroecological techniques were used to identify periods of tree encroachment, changes in age structure, pulses of tree establishment and possible correlations with climatic variables. Dendroecological results indicated that over the last 60-80 years, trees have invaded an average of 30 meters into grasslands on south-facing slopes and flat terrain in southwest Yukon. Ecotones on north-facing slopes appear stable with little advance into grasslands over the last 60 years. Results indicate forest encroachment varies across topography and between tree species. Repeat image analysis was also used to examine landscape changes over a 60-year time period near Kluane Lake. Forest encroachment was investigated using landscape metrics which characterized changes in grassland configuration across three time periods (1947, 1979, 2007) in a 10km2 area. Total grassland area decreased from 214.4 hectares in 1947 to 137 hectares in 2007 and coincided with extensive grassland fragmentation. One hundred and seventy grassland patches were identified in 1947 which increased to 270 patches in 2007. Although tree invasion was found across all topographic gradients, results complement dendroecological analyses with flat terrain and south-facing slopes experiencing the greatest loss of grassland. It is possible that the increase in trembling aspen (Populus tremuloides) on south-facing slopes and flat terrain is due to warmer temperatures in the area. Aspen establishment coincided with warmer temperatures however further work is needed to identify the influence of changes in fire and grazing regimes. Although southwest Yukon grasslands are limited in distribution they are ecologically significant and provide habitat for unique assemblages of flora and fauna. / Thesis (Master, Geography) -- Queen's University, 2012-09-18 01:03:21.524

No description available.

The Peel Watershed Planning Process began in the Yukon and Northwest Territories in 2004. This thesis describes the Peel Watershed Planning Commission and the main interests influencing the planning process. I explore the explanatory potential of several theories draw from urban political economy -- John Logan and Harvey Molotch’s growth machine thesis, Clarence Stone’s regime theory, and Bob Jessop and Neil Brenner’s account of rescaling the state – and suggest that each of these theories can be used to explain certain aspects of Peel Watershed politics. Then I turn to the assimilationist literature on First Nations in Canada – represented by the 1969 White Paper, Tom Flanagan’s First Nations?, Second Thoughts and Frances Widdowson and Albert Howard’s Disrobing the Aboriginal Industry – and contrast it with an alternative literature, represented especially by Paul Nadasdy’s Hunters and Bureaucrats. I argue that these literatures draw attention to aspects of the politics of planning that are neglected in the urban political economy literature, but are of obvious importance in the context of the Peel Watershed. Although questions of community preservation and wealth accumulation are central to the Peel Watershed planning process, worldviews and ways of life are also at stake. This suggests that we have to look at the politics of planning in very broad terms. / Graduate

Thesis (Ph. D.)--University of Toronto, 1988. / Includes bibliographical references (p. 272-287).

Thesis (M.A.)--Simon Fraser University, 1988. / Includes bibliographical references (p. 140-157).

Thesis (M.A.)--Simon Fraser University, 1988. / Includes bibliographical references (p. 140-157).

Thesis (Ph. D.)--University of Toronto, 1988. / Includes bibliographical references (p. 272-287).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. A.)--Oklahoma State University, 2007. / Includes bibliographical references. Also available in electronic format via Internet..

In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The first of these was a 10-speciesexperimental community established from seed and grown in sandboxes at 6 densities with 2 watering levels and 2 fertilizer levels in a factorial design. At the community level, density dependence was observed at all life stages, but was not consistently competitive or facilitative - both emergence and final per plant shoot mass were density dependent, while survival to the end of the season was inversely density dependent. The effect of water was positive at seed emergence whereas fertilizer negatively affected survival. Species specific responses were also dependent on life stage. The final study was a 4-year CDS in the field using 9 common understory species at 6 densities and 3 fertilizer levels. Density negatively affected the community every year except for the first with competition being important at all densities above x1/8th the average community density. Constant final yield was reached in plots above the naturalx1 density for the last two years of the study. Responses to density were species-specific and 7 species declined with increasing density. No facilitative effects were observed. These studies demonstrate that density dependence is important in structuring this unproductive boreal understory habitat. The CDS approach allows us to quantify both the intensity and importance of plant competition at the community and species levels and to determine whether the importance of these biotic interactions depend on abiotic factors. The results clearly show that species-specific responses to biotic interactions are not necessarily the same as community level responses and if we are to understand community structure, it is necessary to use appropriate methodologies. / Science, Faculty of / Botany, Department of / Graduate