Thesis (M.F.)--Michigan. / eContent provider-neutral record in process. Description based on print version record.

Thesis (M.S.) in Ecology and Environmental Science--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 69-73).

Thesis (M.S.) in Forestry--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 53-58).

Thesis (Ph. D.)--University of Chicago, 1915. / "Reprinted from the Botanical gazette, vol. LX, no. 6, 1915." "Contributions from the Hull botanical laboratory 210." "Literature cited": p. 470-471. Also available on the Internet.

A greenhouse study was undertaken to investigate some relationships between nutrition of the host tree, Abies amabilis, as influenced by soil fertility and nitrogen fertilizers, and biology of the balsam woolly aphid, Adelges piceae (Ratz.). Seedlings were reared in two soil regimes - nutrient-deficient mineral soil and enriched humic soil. All trees were infested with aphid larvae, and observations made to determine the influence of soil fertility on the establishment rate of larvae on host trees. Subsequently, groups of 10 trees were treated with foliar nutrients, using ammonium nitrate and urea in various concentrations. The establishment rate of larvae on humic soil host trees was 2.5 times greater than on mineral soil trees. In addition, growth rate of the aphid population on humic soil trees was 37% greater than on mineral soil trees over a four week period. Soil fertility also influenced the life history of the insect. One foliar nutrient adversely affected the aphid population. Over a 10 week period, the aphid population on trees treated with 1% ammonium nitrate decreased by 23%, whereas the control population Increased 30.9%. It is postulated that this foliar treatment manifests its adverse effect primarily by inhibiting initial settling of larvae on the host trees. This inhibition may be related to fertilizer-induced alterations in the amino acid composition of feeding tissue. / Science, Faculty of / Zoology, Department of / Graduate

As management of forests and parks intensifies, pruning of conifers becomes more common. Thus understanding the role of wounds as possible entry courts for decay fungi is vital. In order to study some aspects of this, three natural stands, one in New Brunswick and two in Nova Scotia, which had been pruned 4 to 7 years earlier by industrial or displaced workers, were examined. Five pruned and two unpruned balsam fir (Abies balsamea (L.) Mill.) trees from each stand were dissected; cultural isolations were taken from 207 knots where pruning had caused little or no apparent damage to the bole, and from 169 blazes resulting from less careful prunings. All 15 pruned trees, ranging in age from 23 to 42 years, had decay attributable to pruning which averaged 1.7% of the stem volume. This incidence and volume of decay exceeds that recorded in unpruned trees 40 to 60 years old in New Brunswick. Axe blazes were the major entry court for decay-causing fungis basidiomycetes were associated with 12% of the blazes and with 5% of the more carefully pruned knots. Neither stem nor butt decay was found in the unpruned trees. In a further study, 7 branches on each of 30 balsam fir trees near Fredericton, N. B. were experimentally axe pruned; some carefully, some carelessly; both during tree dormancy and during wet and dry periods of active growth. Thirty additional branches were saw pruned. At periods of 2 to 3 weeks, 5 to 7 months and 17 to 19 months after pruning, cultures were made in the field from 70 of the pruning wounds. Within 2 weeks of the latter period, the trees were dissected, measured and further cultures were made in the laboratory from the same 70 wounds. Eighteen months after pruning, 28 of 30 trees had decay averaging 3.9% of stem volume and basidiomycetes were isolated from 22 (31%) of 70 wounds. In the controls butt decay only occurred in 4 of 10 trees. These studies show: (l) that blazes into sapwood (careless pruning) were more frequently infected than those where little or no sapwood was exposed; (2) the incidence of infection was least in branches pruned during the dry period and about equal for those pruned in the wet-active and dormant periods; and (3) the successional pattern began with imperfect fungi and bacteria, and terminated with decay fungi. / Forestry, Faculty of / Graduate

No description available.

This thesis investigates the impact of two invasive ecosystem engineers on the river banks. Invasive species generate significant global environmental and economic costs and represent a particularly potent threat to freshwater ecosystems. Ecosystem engineers are organisms that modify their physical habitat. Therefore this thesis will explore the interaction of these two types of species and their impacts on the example of the impact of signal crayfish and Himalayan balsam The obtained results indicate that there are few avenues through which invasive ecosystem engineers can influence river bank processes. While many uncertainties remain, due to the intrinsic complexity of river ecosystems, a multitude of anthropogenic stressors that they are increasingly subjected to and a wide array of ecosystem services that rivers provide to people, it is important to consider the role of invasive ecosystem engineers in river management practices. on river banks. The work included analyses and development of conceptual models for the understanding of invasive ecosystem engineers, followed by four research chapters aimed at answering specific questions. A study of signal crayfish impact is primarily focused on the impact of burrows that crayfish dig as shelter and their influence on riverbank erosion. The interaction between habitat characteristics, the occurrence of burrows and erosion is analysed on three different levels of spatial scale: bank section in reach, reach in the catchment and bank section in the catchment. Bank section in reach survey (Chapter 4) focused on a reach heavily impacted by crayfish burrowing on the River Windrush, UK, in order to study the maximum effect of burrowing. Also, smaller spatial extent enabled detailed study of three sets of variables as well as an assessment of the impact that signal crayfish population density has on burrowing. Reach in catchment spatial scale expanded the survey to cover 103 river reaches in the Thames catchment and was based on a combination of habitat information from publicly available online data sets, primarily the River Habitat Survey database and rapid field surveys that recorded burrows and erosion. Bank section in catchment-scale was based on the same 103 sites, but the main focus of field observations were ten metres long bank sections for which habitat, burrows and erosion information were collected. Overall, burrowed banks were more likely to be characterised by cohesive bank material, steeper bank profiles with large areas of bare bank face, often on outer bend locations and were associated with bank profiles with signs of erosion. There were indications that signal crayfish burrowing is contributing to the river bank erosion, but no conclusive results have been made. Study of the impact of the Himalayan balsam was undertaken on eight sites at the River Brenta in Italy and it was focused on three main aspects. Firstly it was established that extent of Himalayan balsam domination over native vegetation varies widely depending on the habitat conditions and native plants encountered. Secondly, it was established that there are no conclusive differences in the extent of erosion and deposition on transects covered by native vegetation and Himalayan balsam. Thirdly, measurement of traits of individual plants showed significant differences in traits of individual plants that are known to have consequences for river bank erosion and deposition.

Thesis (M.Sc.), Memorial University of Newfoundland, 2000. / Restricted until June 2001. Bibliography: leaves 69-74.

Thesis (Ph. D.) in Forest Resources--University of Maine, 2000. / Includes vita. Includes bibliographical references (leaves 134-143).