Thesis (M.S.) in Forestry--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 113-118).

Four general post-fire successional pathways leading to a climax Engelmann spruce (Picea engelmannii Parry)/subalpine fir (Abies lasiocarpa [Hook] Nutt.) forest were identified operating on the T.W. Daniel Experimental Forest in northern Utah. These included initial colonization by seral quaking aspen (Populus tremuloides Michx.), seral lodgepole pine (Pinus contorta Dougl. ex Loud.), colonization by lodgepole pine followed by a low intensity surface fire, and immediate colonization by late successional Engelmann spruce and subalpine fir. Post-fire establishment of the late successional species occurred earliest in the Engelmann spruce/subalpine fir pathway followed by the lodgepole pine and lodgepole pine ground fire pathways, and the quaking aspen pathway . The late successional species 11 grew fastest in the Engelmann spruce/subalpine fir pathway followed by the quaking aspen, lodgepole pine, and lodgepole pine ground-fire pathways. Conceptual models were presented showing how perturbations by fire, insect epidemics, and disease could interact to influence succession and shape the subalpine landscape. The subalpine forest changes through time to facilitate different types of disturbance that have varying effects on succession. In the continued suppression of fire, species and age class diversity will be reduced and disturbances may occur that are larger and more intense than those that have occurred historically.

Northeastern forests are being impacted by unprecedented environmental stressors, including acid deposition, invasive pests, and climate change. Forest health monitoring at a landscape scale is necessary to evaluate the changing condition of forest resources and to inform management of forest stressors. Traditional forest health monitoring is often limited to specific sites experiencing catastrophic decline or widespread mortality. Satellite remote sensing can complement these efforts by providing comprehensive forest health assessments over broad regions. Subtle changes in canopy health can be monitored over time by applying spectral vegetation indices to multitemporal satellite imagery. This project used historical archives of Landsat-5 TM imagery and geographic information systems to examine forest health trends in the northern Green Mountains of Vermont from 1984 to 2009. Results indicate that canopy health has remained relatively stable across most of the landscape, although decline was present in localized areas. Significant but weak relationships were discovered between declining forest health and spruce-fir-paper birch forests at high elevations. Possible causes of decline include the interacting effects of acid deposition, windthrow, and stressful growing environments typical of montane forests.

In order to fully understand the magnitude of the benefits that forests provide, it is crucial to understand the full suite of ecosystem services that they offer. A southern Appalachian red spruce-Fraser fir forest was intensively analyzed using a variety of methodologies to determine the nature and quantity of some of these services. Many hypotheses exist regarding the future of these spruce-fir forests, which were heavily disturbed by the non-native balsam wooly adelgid during the 1980s. Direct measurements over the course of a decade assessed these hypotheses and indicate that this forest is recovering structure and function. The forest is accruing overstory biomass, with vegetation composition on a trajectory towards historic conditions. By using a total forest inventory of all vegetation from overstory trees to understory mosses, rates of productivity and nutrient cycling were determined. Productivity of this forest at low elevations has returned to pre-adelgid levels, while at high elevations productivity is approaching these levels. In the absence of an intact overstory, forest understory vegetation can compensate by disproportionately cycling and retaining nutrients such as nitrogen that would otherwise leach offsite. The understory of this forest provides an important service in nutrient cycling. Our ability to actively manage forests in order to manipulate levels and rates of carbon sequestration was assessed using stand data and the Forest Vegetation Simulator Growth and Yield Model. Silvicultural intervention proved effective at sequestering additional carbon over a no action alternative by the end of our simulation period. This forest provides a variety of ecosystem services and has retained its ability to recover their function after catastrophic disturbance.

In order to fully understand the magnitude of the benefits that forests provide, it is crucial to understand the full suite of ecosystem services that they offer. A southern Appalachian red spruce-Fraser fir forest was intensively analyzed using a variety of methodologies to determine the nature and quantity of some of these services. Many hypotheses exist regarding the future of these spruce-fir forests, which were heavily disturbed by the non-native balsam wooly adelgid during the 1980s. Direct measurements over the course of a decade assessed these hypotheses and indicate that this forest is recovering structure and function. The forest is accruing overstory biomass, with vegetation composition on a trajectory towards historic conditions. By using a total forest inventory of all vegetation from overstory trees to understory mosses, rates of productivity and nutrient cycling were determined. Productivity of this forest at low elevations has returned to pre-adelgid levels, while at high elevations productivity is approaching these levels. In the absence of an intact overstory, forest understory vegetation can compensate by disproportionately cycling and retaining nutrients such as nitrogen that would otherwise leach offsite. The understory of this forest provides an important service in nutrient cycling. Our ability to actively manage forests in order to manipulate levels and rates of carbon sequestration was assessed using stand data and the Forest Vegetation Simulator Growth and Yield Model. Silvicultural intervention proved effective at sequestering additional carbon over a no action alternative by the end of our simulation period. This forest provides a variety of ecosystem services and has retained its ability to recover their function after catastrophic disturbance.

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU

Guilds of species that share ecological similarities or recent ancestors are often the basis of studies concerning habitat partitioning. An interesting result of many of these studies is that means of partitioning in one area of sympatry may be different from those in disjunct areas of overlap. Here, we quantified the differences in habitat preference of two forest thrushes in the southern Appalachian Mountains. The Hermit Thrush (Catharus guttatus) has recently expanded its breeding range south along the spine of the Appalachians into the spruce-fir forests of Virginia, North Carolina, and Tennessee. There, it shares breeding habitat with the congeneric Veery (C. fuscescens), previously the only forest thrush breeding in this area. We used several multivariate analyses of habitat variables within both species' territories to understand how these species partition the available habitat and to test if these means of partitioning are similar to those found by other studies. We calculated the niche overlap to be 0.248, indicating that the habitat structures preferred by these two species are highly distinct. Hermit Thrushes generally preferred forest with a high degree of canopy closure, high percent coverage of leaf litter, and low percent cover below 3.0 m. Veery territories generally had a high percent of cover between 0.5 and 3.0 m (i.e., the shrub layer) and less canopy closure than the Hermit Thrush plots. Our data suggest that the Hermit Thrush is expanding south because it is attracted to the maturing of the spruce forests in this region.

Guilds of species that share ecological similarities or recent ancestors are often the basis of studies concerning habitat partitioning. An interesting result of many of these studies is that means of partitioning in one area of sympatry may be different from those in disjunct areas of overlap. Here, we quantified the differences in habitat preference of two forest thrushes in the southern Appalachian Mountains. The Hermit Thrush (Catharus guttatus) has recently expanded its breeding range south along the spine of the Appalachians into the spruce-fir forests of Virginia, North Carolina, and Tennessee. There, it shares breeding habitat with the congeneric Veery (C. fuscescens), previously the only forest thrush breeding in this area. We used several multivariate analyses of habitat variables within both species' territories to understand how these species partition the available habitat and to test if these means of partitioning are similar to those found by other studies. We calculated the niche overlap to be 0.248, indicating that the habitat structures preferred by these two species are highly distinct. Hermit Thrushes generally preferred forest with a high degree of canopy closure, high percent coverage of leaf litter, and low percent cover below 3.0 m. Veery territories generally had a high percent of cover between 0.5 and 3.0 m (i.e., the shrub layer) and less canopy closure than the Hermit Thrush plots. Our data suggest that the Hermit Thrush is expanding south because it is attracted to the maturing of the spruce forests in this region.

Sixteen stands representing a range of structural variation in aspen, mixed aspen-conifer, and spruce-fir communities of the Wasatch Plateau, Utah, were censused by the sample count method. The stands were classified as eleven community types based on the understory dominants or indicator species and the cover types. Fifty bird species were recorded during the two seasons; thirty-two occurred in aspen cover, forty-four in mixed aspen-conifer cover, and twenty-two in spruce-fir. Comparisons of the composition and density of bird populations were made between uniform stands of a single life form and more structurally complex stands of either single or mixed life forms. Limiting factors in the structural characteristics of the stands were identified for birds restricted to particular stands. Low avian similarities between some aspen stands were attributed to the differences in structure between the stands. Bird species which favored the deciduous life form tended to decrease in abundance in the mixed stands as the canopy coverage of conifers increased, and they were absent in the spruce-fir stand. Coniferous forest bird species were more abundant in mixed stands with high coniferous coverage than in the aspen-dominated stands. Low individual bird numbers were found in the conifer stand of uniform small trees. Several vegetational characteristics of the stands were evaluated to determine if any was an index of forest heterogeneity predictive of bird species diversity. The habitat features of ecological relevance to most of the bird species were the size, spacing, and life form of the trees. The diversity of the distribution of diameter measurements at breast height for the tree species was predictive of bird species diversity. High diversity in the distribution of tree measurements at breast height was correlated with variation in tree height, tree canopy diameter, and the spacing of the life forms. It was therefore an index of three dimensional environmental patchiness, easily visualized by the variation in life forms and the number of stories within the stand.

The Hermit Thrush is a new breeding bird in the Southern Appalachian high-elevation mountains, having expanded its range southward over the last few decades. Here it is sympatric with the Veery, a congeneric breeding resident. In order to more fully understand why the range expansion took place and to understand more about the local ecology of the newly arrived bird, I measured several habitat variables in 30 Hermit Thrush and 24 Veery territories. Principal Components Analysis and Cluster Analysis brought to light several patterns of habitat preferences for these 2 species. Hermit Thrushes prefer territories with more leaf litter on the ground and less shrub density than Veery territories. Competition between these species should remain low, as their niche differences brought to light in this study should enable them to breed in close proximity to each other in these high-elevation mountains.