Thesis (Ph. D.)--University of British Columbia, 1999. / Includes bibliographical references (leaves 172-180).

No description available.

Araucaria angustifolia é a única conífera nativa com importância econômica no Brasil. A espécie está incluída na lista oficial de espécies de plantas ameaçadas de extinção. A embriogênese somática é considerada como uma das ferramentas biotecnológicas mais promissoras na área de biotecnologia de plantas. A identificação de marcadores, que possam ser utilizados, para a seleção de genótipos aptos ao desenvolvimento do embrião somático é altamente desejável, uma vez que o desenvolvimento apropriado do embrião somático é extremamente dependente do genótipo. O presente trabalho teve como objetivo estudar e identificar marcadores bioquímicos e moleculares associados à competência para embriogênese somática em A. angustifolia. Culturas embriogênicas de genótipos com diferentes potenciais embriogênicos apresentaram diferenças nos parâmetros bioquímicos e moleculares avaliados (Poliaminas, expressão dos genes AaSERK1 e AaPP2C, proteoma). O presente trabalho propõe a utilização destes parâmetros como possíveis marcadores do potencial embriogênico no sistema A. angustifolia. / The Araucaria angustifolia is the only native conifer species with economical importance in Brazil. Recently, the species was included in the official list of endangered plant species. Somatic embryogenesis, i.e., in vitro asexual production of embryos is considered one of the most promising biotechnological tools in the area of plant biotechnology. Since the development of somatic embryos is dependent of the genotype, the identification of markers that could be used in the selection of genotypes which can develop somatic embryos is highly desirable. The main objective of the present work is to study and identify biochemical and molecular markers associated with competence for somatic embryogenesis in A. angustifolia. The evaluation of biochemical and molecular aspects (Polyamines, AaSERK1 and AaPP2C gene expression and proteome) indicated differences between embryogenic cultures of genotypes with different embryogenic potential. This work proposes the utilization of these parameters as possible markers of embryogenic potential in the system A. angustifolia.

Nutritional stress has been reported in planted and naturally-regenerated conifers growing in association with an ericaceous species, salal (Gaultheria shallon Pursh), in cutovers previously occupied by old-growth western redcedar (Thuja plicata Donn) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) (CH sites) on northern Vancouver Island. No such stress was apparent in cutovers previously occupied by natural, second growth western hemlock and amabilis fir (Abies amabilis (Dougl.) Forbes) stands (HA sites) that developed following windthrow in 1907. The CH ecosystem type occupies as much as 100,000 ha in coastal British Columbia. In the spring of 1987, a series of field and pot experiments was initiated to investigate some of the ecological processes affecting the early growth of conifers on recently logged and burned 2- to 10-year-old CH and 2- to 4-year-old HA sites. The overall objective of the research was to quantify some of the possible factors limiting early conifer growth on northern Vancouver Island. The research encompassed studies of: (1) below- and above-ground non-crop vegetation recovery, forest floor nutrient availability and soil microenvironmental modification following clear-cutting and burning; (2) competition for nutrients by the non-crop vegetation; (3) interference by salal of the mycorrhizal development on conifer seedling roots; (4) conifer seedling growth under several different experimental conditions, and; (5) relationship between microsite factors and western redcedar seedling growth within clear-cut and burned CH sites. Salal was the main non-crop species found on the CH sites. It reestablished itself rapidly, both above- and below-ground, following clear-cutting and burning on this type of site. The total above-ground vegetation biomass quadrupled from 1372 kg ha ̄¹on the 2-year-old CH sites to 5574 kg ha ̄¹on the 8-year-old CH sites, whereas the total below-ground biomass increased six times from 1908 kg ha ̄¹ on the 2-year-old CH sites to 11415 kg ha ̄¹ on the 8-year-old CH sites. Similar amounts of total above-ground non-crop biomass were found on HA cutovers for the first 4 years, but the non-crop vegetation was composed of half salal half fireweed (Epilobium angustifolium L.). The regrowth of the non-crop vegetation immobilized annually 9 and 0.9 kg ha ̄¹of N and P, respectively, on the CH sites during the first eight years. This was estimated to represent potentially between 30 and 45% of the available N on these sites. A model of the development of live fine-root, leaf, stem and rhizome biomass of salal over a 60 year period is proposed based on the result of this study and of other studies. This model suggests that the net immobilization of nutrients in salal biomass will cease between 10 and 20 years after clear-cutting and burning as salal stops expanding its biomass. This model implies that the nutritional stress caused by salal should decline after 10 to 20 years at which time conifer nutrition and growth should slowly improve, especially as salal is eliminated by light competition as the conifer canopy begins to close. Several biotic and abiotic factors were studied in relation to their possible effects on the early growth of western hemlock, Sitka spruce and western redcedar. The growth of these three conifer species was compared between 2- to 4-year-old CH cutovers (2+B CH), 8- to 10-year-old CH cutovers (8+B CH), and 2- to 4-year-old HA cutovers (2+B HA) with and without the influence of the non-crop vegetation. No moisture deficit was measured in the field throughout the year on all sites. Both the growth of the conifers and the availability of N (+36%) and P (+25%) were increased by the removal of the non-crop vegetation; however, no difference in cellulose decomposition and soil moisture, and only very small difference in soil temperature was measured. The better conifer growth on 2+B HA > 2+B CH > 8+B CH without the influence of the non-crop vegetation was associated with an overall better forest floor nutrient status; however, no difference in soil moisture and pH, and only small difference in soil temperature were measured. Western redcedar and western hemlock were the best growing species on CH and HA sites, respectively. Both western hemlock and Sitka spruce (Picea sitchensis) were very responsive to the different site conditions (CH vs HA sites) and to planting treatments that increased or decreased conventional measures of nutrient availability caused by the different treatments, whereas western redcedar was not. The presence of salal was found to have no effect on the total percent mycorrhizae found on the roots of the three conifer species studied three years after planting. Both field and pot experiments yielded comparable results. Slow-release fertilizer, at the time of planting, increased growth only for the first two years after application. Western redcedar growth was significantly greater in depressions than on flats and mounds, but this difference was not related to any major differences in the forest floor variables measured between the three microtopographic positions. These results indicate that the nutritional stress and poor growth reported in conifers, especially in Sitka spruce, on CH cutovers on northern Vancouver Island can be explained by a combination of (1) inherently low forest floor fertility in cutovers originating from the old-growth CH forests, (2) salal competition for scarce nutrients and their immobilization in salal biomass, and (3) declining site fertility caused by the termination of the flush of nutrients that occurs in the immediate post-logging and burning period on CH sites. / Forestry, Faculty of / Graduate

No description available.

The object of this study was to determine whether or not Lodgepole pine is successfully invading meadows near ponds in the western Uinta Mountains as a preliminary step to the invasion of the Spruce-Fir climax forest. Line transects were established at three sites near Trial Lake extending from forest to wet meadow. Along these transects the soil was studied to determine percent organic matter, pH, depth to mineral soil, and texture. Also the depth of the water table was measured and the topography plotted. The age and size of the trees along the transect was determined, and the extent of some root systems was noted. Conifers found growing in the dry meadow were stunted and no conifers were found growing on peat deposits over 17 inches. The water table was found within about 8 inches of the surface and the soil conditions suggested poor aeration. The combination of peat and high water level accounted for the stunting of the trees. The trees were apparently unable to convert the dry meadow to forest and thus, the climax for hydrarch succession in this area is a meadow vegetation of grasses and sedges instead of the conifer forest.

Six forest areas destroyed by fire representing different seral stages of aspen development and conifer invasion were studied to determine successional dynamics and the related livestock and big game use. Factors measured were: (a) age, basal area, density and frequency of aspen and conifer trees; (b) density and frequency of under-story species; (c) forage production for forbs, grasses, and browse, and (d) animal-days use for deer, cattle and sheep. Aspen appeared in the community the spring following the fire and conifers appeared fifteen to twenty years later. Conifers had begun to dominate aspen on an eighty-two year old stand. The density and frequency of understory species was influenced by grazing pressure, age of the cormnunity and conifer basal area. Maximum densities were reached twenty years after the fire. Forage production was influenced by the age of the community and conifer basal area. Maximum forage production was reached on the twenty-one year old burn. Animal use was influenced by the amount of forage production, conifer basal area and competitive use by other animals.

Procerum root disease of eastern white pine (Pinus strobus L.), caused by Leptographium procerum (Kendr.) Wingf., has been epidemic in Virginia Christmas tree plantations since 1990. Symptoms of chlorosis, wilt, and decreased apical growth resemble those of water stress. Resin infiltration of the xylem at the stem base may be responsible for vascular occlusion leading to severe water deficits and mortality. The pathogen has been isolated from the roots of ozone-sensitive eastern white pines in the field, although not from nearby tolerant trees, and it may be that ozone sensitivity predisposes the trees to infection. The objectives of my Studies were to investigate the physiology of diseased white pines, and to determine the effects of ozone fumigation on disease development. Impacts of vascular occlusion upon host water relations and gas exchange were investigated in 8-yr-old, plantation-grown, white pine Christmas trees. Disease severity was estimated as the proportion of resin-soaked cross-sectional area at the base of the stem. The linear response of a suite of six physiological variables to disease severity was highly significant. Individually, the variables pre-dawn water potential, daily change in pre-dawn to mid-day water potential, stomatal conductance, and photosynthetic and transpiration rates all decreased significantly with increasing disease severity. Fumigation studies were conducted on white and loblolly (P. taeda L.) pine seedlings to determine if ozone exposure increased the incidence of root disease or the amount of stem tissue colonized by L. procerum. Roots were inoculated by soil drenching with conidial suspension, and stems were wounded at the base and inoculated with mycelium. Beginning 24 h post-inoculation, and for 14 consecutive days, seedlings were fumigated in closed chambers with charcoal-filtered air or 200 ppb ozone for 5 h/day, then removed to a charcoal-filtered greenhouse. Six weeks post-inoculation, root and stem tissue were plated on a medium selective for L. procerum. Ozone treatment did not significantly affect the proportion of diseased roots per seedling or the vertical colonization of stem tissue in seedlings of either species. / Ph. D.

Southern Appalachian spruce-fir sky islands are globally threatened, boreal relict forests where red spruce (Picea rubens) and Fraser fir (Abies fraseri) are dominant. Fraser fir dominates at the highest elevations with spruce-fir and spruce-dominated stands at middle elevations and hardwoods associating at lower elevations. A primary concern is encroachment of hardwoods upslope as climate change-driven milder temperatures and high precipitation confine spruce-fir forests to even higher elevations. We performed a dendrochronological analysis of growth rates in red spruce, Fraser fir, and competing hardwoods between cover types and slope aspects at six sky islands. We created linear models to test effects of aspect, cover type, and year on basal area growth measurements of red spruce, Fraser fir, and hardwoods to assess effects of competition. Growth rates were significantly affected by species, aspect, cover type, and year, and generally increased over time. Red spruce growth rates varied by combination of aspect and cover type but were greater than those of hardwoods on northern and southern aspects. Fraser fir growth rates were negative on southern-facing fir-dominated stands but increased in all other stands with the highest growth rates found in fir-dominated stands. The differences we report by cover type and aspect could help conservation practitioners prioritize treatment locations to improve climate resiliency. / Master of Science / Southern Appalachian spruce-fir sky islands are globally threatened, boreal relict forests where red spruce (Picea rubens) and Fraser fir (Abies fraseri) are dominant. Fraser fir dominates at the highest elevations with spruce-fir and spruce-dominated stands at middle elevations and hardwoods associating at lower elevations. A primary concern is encroachment of hardwoods upslope as climate change-driven milder temperatures and high precipitation confine spruce-fir forests to even higher elevations. We performed a dendrochronological analysis of growth rates in red spruce, Fraser fir, and competing hardwoods between cover types and slope aspects at six sky islands. We created linear models to test effects of aspect, cover type, and year on basal area growth measurements of red spruce, Fraser fir, and hardwoods to assess effects of competition. Growth rates were significantly affected by species, aspect, cover type, and year, and generally increased over time. Red spruce growth rates varied by combination of aspect and cover type but were greater than those of hardwoods on northern and southern aspects. Fraser fir growth rates were negative on southern-facing fir-dominated stands but increased in all other stands with the highest growth rates found in fir-dominated stands. The differences we report by cover type and aspect could help conservation practitioners prioritize treatment locations to improve climate resiliency.

Land use practices and exposure to low impact disturbances associated with an urban environment can alter forest structure and function. Past and ongoing research in Forest Park, a large urban forest in Portland, Oregon, suggests that mature mixed Douglas-fir (Psuedotsuga meziesii)-hardwood stands in the more urban end of the park lack a shade-tolerant conifer understory composed of the late successional conifer tree species, such western hemlock (Tsuga heterophylla) and western red-cedar (Thuja plicata). 5-year plot remeasurement data that characterizes productivity and mortality patterns did not show a strong relationship to urban proximity. Plot productivity was generally consistent with values taken from studies of other similarly aged (~100 years old) Douglas-fir /Western Hemlock stands. Mortality was highest in rural plots, and was driven by large windthrow events to canopy trees. Soil organic matter, soil pH, and depth of organic horizon indicated a legacy of soil impact in urban areas most impacted by past intensive logging. The urban mature plot had higher mean soil pH at site (5.87, se: ±0.06) compared to a rural mature, and old growth reference sites located within the park. Although surface organic and A layer soil horizon depth was thinnest at the urban mature site, soil organic matter was not found to be significantly different across sites. Light detection and ranging (LiDAR) data showed that old-growth plots and plots in the middle section of the park had the highest degree of canopy structure as measured by Rumple and standard deviation of point elevation. Measures of stand height showed OG plots and urban plots to have the tallest trees. Rural plots showed a high degree of variability in all LiDAR metrics, showing a wider range of stand height and complexity than urban and middle plots. These results suggest that past land-use and urban proximity affect plot level productivity, soil quality, and above-ground canopy structure in Forest Park. These results clarify how the lack of late-successional tree species might be most linked to differing histories of intensive logging activity within the park. Reduced old-growth legacy features (remnant seed trees, coarse woody debris) in plots with a clear history of aggressive clear-cuts has led to a reduction in regeneration of western hemlock and western red-cedar in the understory.