Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1997. / Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2003. / Bibliogr.: f. 116-131. Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Min.) -- Université du Québec à Chicoutimi, 2005. / Bibliogr.: f. [85]-95. Document électronique également accessible en format PDF. CaQCU

Thesis (M.Sc.), Memorial University of Newfoundland, 1999. / Bibliography: p. 208-219.

Competition from non-crop vegetation decreases the productivity of conifer plantations across Canada. The objectives of this research were: (1) to develop reliable indices of perennial, interspecific competition; (2) to compare the responses of black spruce and jack pine seedlings to tree and brush competition in northern Ontario; and (3) to identify the silvicultural implications of the responses. An examination of potential components of a competition index considered measures based on hemispherical photographs, fractal geometry, stand maps, and mensurational data from 360 seedling-centred plots for each of the two crop species. Reliable competition indices should be simple formulations which include horizontal and vertical dimensions and which express the amount of competition relative to the size of the seedling. The optimum index was found to be the area of competing canopy on hemispherical photographs, relative to the seedling leaf area. An alternate index, requiring no elaborate equipment, was the sum of the competing stem volumes (relative to the seedling stem volume) of the largest competitor in each quadrant surrounding the seedling. Comparisons of crop tree responses were made using functional growth analysis, replacing the conventional time axis with a competition axis. The relationship between growth and competition was adequately modelled with a power exponential composite function. Jack pine and bare root stock of both species maintained superior growth despite greater sensitivities to competition, compared to black spruce and container stock, respectively. Thus, jack pine or bare root stock of black spruce would outperform the alternatives if tending were delayed, but competition should be removed in all cases to capture the maximum growth potential. The rate of growth decline in response to competition was consistently greatest at the lowest competition levels, indicating that no beneficial effect on growth was provided by a light cover of non-crop vegetation. Allometric analyses indicated that black spruce had a greater morphological plasticity than jack pine. At high competition levels black spruce allocated more biomass to branches and foliage, at the expense of stem and roots. Jack pine demonstrated no such adjustment in allocation pattern, but followed a strategy of stress avoidance through sustained high growth rates. / Forestry, Faculty of / Graduate

The annual earlywood, latewood and total radial growth in black spruce from organic and mineral soils of varying depths, composition, ad moisture regimes of three locations in Ontario were investigated. Growth in relation to site, temperature, and precipitation was assessed. Statistical analyses of the radial width increments expressed as percentages of trend over thirty years' growth, showed significant crossdating. Total annual and earlywood increments are correlated with mean March-April and March temperature; latewood increments are not. There is no relationship between growth and precipitation. These findings hold for trees from organic and mineral soil sites up to approximately five hundred miles apart. It is concluded that spring mean temperature is independent of site or other climatic factors, and results suggest that spring temperature indirectly controls radial growth. Primary direct controls are presumably internal, i.e. physiologic and genetic. / Thesis / Doctor of Philosophy (PhD)

Changes in forest ecosystem vegetation also bring about changes to the associated soil. In order to maintain forest productivity, it is important to know the effects of tree species upon the soil, especially the influence of deciduous versus coniferous tree species. Many deciduous species increase pH, nitrogen, base saturation and/or accumulation of organic matter in the forest floor. The chemical properties of the forest floor may, in turn, influence the chemical properties of the underlying mineral soil. If a tree species significantly alters the soil, then silviculturists may consider crop rotation between deciduous and coniferous trees or growing mixed-species stands to maintain greater nutrient availability and maintain site productivity. Trembling aspen (Populus tremuloides) and black spruce (Picea mariana) may occupy similar sites in the North American boreal forest. Shade-intolerant aspen is generally a seral species while shade-tolerant black spruce can be a seral species but also forms a major component in late successional stages. This study investigated differences in nitrogen-related soil properties between trembling aspen and black spruce stands on upland sites in the BWBS zone of northeastern BC. We asked two questions: (1) are the differences in soil nutrient properties manifested in both forest floor and mineral soil? (2) To what extent are these differences reflected in the floristic composition of understory vegetation?

Accurate and reliable predictions of site index (height of dominant trees at a reference age, usually 50 years at breast-height) for timber crop species is essential for silvicultural site-specific decision making. Site index can be predicted from site quality once the relationship between site index and site quality has been quantified. Site quality is defined as the sum of all environmental factors affecting the biotic community, such as the factors directly influencing the growth of vascular plants (light, heat, soil moisture, soil nutrients, and soil aeration). Since these factors vary greatly in time, indirect estimates of site quality have widely been used as predictors for site index in various multiple regression models. Trembling aspen (Populus tremuloides Michx.) is the most widely distributed broadleaf species in British Columbia, especially in the Boreal White and Black Spruce (BWBS) biogeoclimatic zone. Growing this species for sustainable timber production requires a good understanding of its productivity attributes and accurate predictions of its growth. This extension note presents (1) relationships between trembling aspen site index and some indirect measures of site quality, and (2) site index prediction models using the indirect measures of site quality as predictors.

The boreal forest is confined to the Northern Hemisphere and is the most continuous and extensive forest in the world. In North America boreal forest extends from the Pacific to Atlantic coast spanning over 10° latitude. White spruce (Picea glauca (Moench) Voss), black spruce (P. mariana (Mill.) B.S.P.), and trembling aspen (Populus tremuloides Michx.) are among the dominant tree species. Black spruce and trembling aspen may form pure stands and occupy similar sites as their edaphic amplitudes overlap; however, spruce is rare on water-deficient sites and aspen does not tolerate excess water. Despite many studies conducted in the North American boreal forest, little is known about relationships between the boreal understory vegetation and softwood or hardwood canopy species in different climate regions. Furthermore, the variation in species diversity and succession between the stands dominated by coniferous trees and those dominated by broadleaved trees within the same region is unknown. The objectives of this study are to determine (1) the difference in the species diversity and floristic composition of understory vegetation between black spruce and trembling aspen stands within the same climatic region, and (2) how the species diversity and floristic composition of understory vegetation in each stand type vary with climate, and soil moisture and soil nutrient conditions.