A canker on the main stem of oppressed western hemlock (Tsuga hetero hylla (Rafn.) Sarg.), 1 to 3 inches in diameter at breast height, was found at Powell River and Tumour Island, British Columbia. The canker is irregularly elliptical, with a conspicuous resin exudation in the early stages. The canker appears to be annual. A species of Cephalosporium (Fungi Imperfecti, Moniliales) was consistently isolated from cankers collected at Powell River. The pathogenicity of the organism has not been proven to date. The growth and hyphal characters of the organism, and the temperature-growth relations of the organism in culture are described. The conidial apparatus of the organism was investigated. Attempts to produce the perfect stage in culture were unsuccessful. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

The vertical rate of spread of dwarf mistletoe was studied in two actively growing, young hemlock stands. This was done by determining the height and age of successive oldest and highest female infections. The rate of spread was calculated by dividing the sum of the heights of advances by the total number of years lapse between successive advances. The mean vertical spread rate was 2.1 ± 0.1 ft./yr. in a relatively open stand and 1.0 ± 0.1 ft./yr. in a relatively dense stand. The mean rate of tree growth during the maximum growth phase in the open stand was 2.5 ft./yr. and for the dense stand 1.5 ft./yr. However, over the past 25 years, the growth rate of the trees in the open stand was 1.9 ft./yr. and for the dense stand 1.1 ft./yr. The number of new infections per year increased geometrically, doubling every four years in both the dense and open stands. However, the geometric increase levelled off six years ago in the open stand and five years ago in the dense stand. During the maximum growth phase of hemlock in an open and dense stand, the most photosynthetically active upper portion of the crown remains free of mistletoe infection. Until the senescent phase is reached, the trees can be expected to outgrow the mistletoe and intensification will be restricted to the lower portions of the crowns. It is tentatively concluded that provided there is no overstory seed source and no disruption of the natural stand, such as thinning, dwarf mistletoe on hemlock will not become serious until the rate of height growth of the trees falls below the rate of vertical spread, i.e., not until after the presently accepted rotation age. / Forestry, Faculty of / Graduate

The number, height and age of western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones) infections were recorded in two western hemlock (Tsuga heterophylla (Raf.) Sarg.) stands (44 and 130 years old) located on similar sites on the University of British Columbia Research Forest at Maple Ridge, B.C.. The rapid decrease in numbers of infections with infection age was shown to be largely due to infection mortality. The rate of intensification of the disease expressed as "doubling time" was estimated to be 40 or more years in both stands. Also estimated was a rate of vertical spread of .15 metres per year. The results differed markedly from those of other studies in similar stands, which generally predict "doubling times" of 2 to 4 years and vertical spread rates of up to .5 metres per year. / Forestry, Faculty of / Graduate

Thesis (M.S.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 53-56). Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 94-102). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 42-48). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 108-115). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 93-98). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1980. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

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