Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6131. Advisers: Gary L. Rolfe; Jeffrey O. Dawson. Includes bibliographical references (leaves 233-242) Available on microfilm from Pro Quest Information and Learning.

This study examines the importance of short-term climate variability when simulating forest succession using ecological process models. A version of the FORSKA2 forest gap model was modified for use with daily climate data and applied along a transect of sites crossing the boreal region in central Canada, including the aspen-parkland and forest-tundra ecotones where impacts of climatic change on forest ecosystems could be particularly significant. The model's sensitivity to forcing with daily climate observations compared to monthly mean and long term averages of monthly mean climate data was investigated. Inclusion of daily climate (minimum and maximum temperature and total precipitation) improved the simulations of key characteristics of present-day forest along the transect, and was particularly important at the ecotones. The results demonstrate that changes in variability associated with future change in mean climate are likely to be important when trying to predict boreal forest responses to projected future climate change. Ideally, the use of projected daily climate data or data based on the statistical characteristics of daily climate is highly recommended for future impact studies. A number of approaches to further improve the functioning of the model are also presented.

Abstract not available.

Selection-cutting is the preferred method of logging in northern hardwood forests, because it is thought to favor the regeneration of valuable, shade-tolerant trees, maximize long-term productivity, and increase the health, quality and economic value of residual trees. Claims have also been made for the ecological sustainability of selection cutting, in particular that it: (a) preserves soil fertility; (b) maintains natural canopy composition; (c) protects plant and animal habitat. I evaluated these claims by studying the effects of selection-cutting on several measures of soil fertility (Ca, Al, Ca/Al molar ratios, pH), canopy composition and tree regeneration, herbaceous layer composition, and structural features related to habitat quality (cavity trees, snags, coarse woody debris) in 55 stands ranging from newly cut to old-growth (not all data overlaps). I found that forest growth after selection-cutting depletes soil solution calcium and lowers soil solution Ca/Al molar ratios, posing a threat to long-term forest health and productivity, particularly at higher elevations and in sites on siliceous bedrock. I found that selection-cut stands dominated by red oak (Quercus rubra) are converting to sugar maple (Acer saccharum) stands, posing a threat to both canopy and herbaceous layer diversity. I found no lasting effects of selection-cutting on herbaceous layer composition, diversity or quality, but I found indirect threats from the conversion of red oak stands to sugar maple and from depletion of soil solution calcium. Finally, I found that current selection-cutting practices generally do not meet published targets for large trees, cavity trees, snags and coarse woody debris, but that they probably could meet those targets with minor changes to cutting practices. I conclude by discussing the implications of these results for the management of northern hardwood forests.

The introduction of Sitka black-tailed deer, Odocoileus hemionus sitkensis Merriam, to Haida Gwaii (Queen Charlotte Islands, B.C., Canada) in the late 19th century provides a valuable opportunity to understand the long-term effects of deer populations on the vegetation of the North American temperate rain forest. We conducted two island-based experiments to investigate the effect of Sitka black-tailed deer on the forest understorey vegetation of this archipelago. In the first experiment we used a set of seven small islands (<15 ha) with different browsing histories (more than 50 years of deer presence, less than 20 years of deer presence, and no evidence of any deer presence) to test the effects of deer on plant cover, species richness and community composition. Browsing history was inversely proportional to both vegetation cover and plant species richness. Modification of the forest understorey plant communities followed a series of steps towards a greatly simplified community of plants possessing mechanisms to keep developing plant tissue inaccessible to deer. In the second experiment we utilized the cull of Sitka black-tailed deer from two large islands (295 ha and 170 ha) to investigate the release of forest plant communities from deer browsing. Using a paired-island approach, deer were culled on two experimental islands but remained on three adjacent control islands. Clear increases in species richness and cover as well as changes in the community composition of the forest understorey of experimental islands in the five years following the initiation of culls suggested a quick return to the forest understorey communities thought to exist before deer modification. However, failure of key shrub species to establish, coupled with the development of closed canopy stands of Sitka spruce, Picea sitchensis, suggests possible alternate stable-states for some communities.

No description available.

No description available.

Perenniporia phloiophila (Aphyllophorales: Polyporaceae) colonizes the bark of live oak (Quercus virginiana Mill.) and is known only in the southeastern United States in this host. Cultural characteristics and mating systems of P. phloiophila and P. medulla-panis, vegetative incompatibility of P. phloiophila and temperature relationships and decay capacities of vegetative isolates of P. phloiophila, P. ohiensis and P. fraxinophila were investigated. Cultural studies indicate macroscopic and microscopic differences between the four species. Antagonistic hyphal interactions developed between different vegetative isolates. Self crosses were compatible. Optimum temperature ranges and maximum growth temperature differed for all species. Mating test results of both species indicate their heterothallic tetrapolar nature. Woods differed significantly in percent weight loss (PWL) caused by each Perenniporia species. No significant difference occurred between different isolates of the same species tested on the same wood. PWL was greatest on oak wood for all fungal species tested.

Data were collected on woody vegetation for 10 years in 6 undisturbed plant communities including slash pine forest, wet prairie, hardwood hammock, edge and interior old-growth cypress forests, and freshwater marsh at National Audubon Society's Corkscrew Swamp Sancturary in South Florida. Forested communities all showed a trend toward greater successional maturity. Numbers and total basal areas generally decreased over the 10 year period for early successional species and tropical species affected by the 1982 freeze in hammock and edge cypress communities. Otherwise, total basal areas steadily increased for all species in the forested communities. Initially the slash pine forest contained only canopy pine, but hardwoods entered the sites 3-4 years after fire and continued to increase in number throughout the study. Woody vegetation in the two marsh communities were less stable, partially due to fire. Fire and hydrologic conditions had measureable impacts on community structure and growth patterns.

Fire-scarred cross-sections from coast redwood (Sequoia sempervirens) at two sites were dendrochronologically dated and used to develop a fire history. Redwood offers a challenge for dendrochronological study due to ring wedging and complacency. Crossdating was successful in 12 of 24 trees. The fire history was developed by comparison of fire scars and fire-associated ring characteristics (resin ducts, double latewood, growth releases, and ring separations) recorded in ring series. Using only dates of fire scars from the first fire in 1714 to the last in 1962, the mean fire interval (MFI) was 9.9 years. MFI for the best represented presettlement segment 1714-1881 was 8.0 years. Using all fire-associated ring features, MFI 1714-1962 was 7.0 years and 1714-1881, 6.0 years. Use of all fire-associated ring characteristics is argued to be a more accurate representation of past fire frequency. MFIs determined are less than others reported for coast redwood and suggest fire frequency in redwood may have been underestimated in past studies.