Forest Sciences Commons^™

Reburns Of High Severity Patches: Effects On Ponderosa Pine Regeneration And Plant Community Composition, Nadav Mouallem

All Graduate Theses and Dissertations, Fall 2023 to Present

The area burned in high severity fire as well as the proportion of fires burning at high severity have been increasing in southwestern ponderosa pine (Pinus ponderosa) forests since the 1980s. These fires often contain large patches (>100 ha) of 100% tree mortality, which are a concern as they can lead to the establishment of nonnative species and conversion to non-forest vegetation. And, with an increasing amount of fire on the landscape, high severity patches are reburning. However, information on the ecological trajectory of reburns of high-severity patches as well as the utility of remotely sensed burn severity metrics …

Effect Of Foliage And Root Carbon Quantity, Quality, And Fluxes On Soil Organic Carbon Stabilization In Montane Aspen And Conifer Stands In Utah, Antra Boča

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Soil organic carbon (SOC) positively affects many soil properties (e.g., fertility and water holding capacity), and the amount of carbon (C) in soil exceeds the amount in the atmosphere by about three times. Forest soils store as much C as is found in trees. Tree species differ in their effect on SOC pools. Quaking aspen forests in the Western US often store more stable SOC in the mineral soil than nearby conifers. During the last decades a decline in aspen cover, often followed by conifer encroachment, has been documented. A shift from aspen to conifer overstories may negatively affect the …

Spatiotemporal Modeling Of Threats To Big Sagebrush Ecological Sites In Northern Utah, Alexander J. Hernandez

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This study tested the performance of classification, regression, and ordination techniques to evaluate the spatiotemporal dynamics of threats to big sagebrush ecological sites. The research was focused on invasion by annual exotic grasses and encroachment by woodlands.

We sought to identify those areas that have had a persistent coverage of cheatgrass (Bromus tectorum) in big sagebrush ecological sites. We took advantage of the contrast in greenness between multi-temporal (within one year) remotely sensed vegetation indices captured in the spring and summer to find a distinct phenological signature that allowed mapping cheatgrass. We utilized support vector machines (SVM) to classify three …

Comparison Of Water Dynamics In Aspen And Conifer: Implications For Ecology Water Yield Augmentation, Eric Martin Lamalfa

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Differences in water dynamics between deciduous aspen (Populus tremuloides) and co-occurring evergreen conifer species in the Northern Rocky Mountains result from complex physical and biological interactions. A comprehensive evaluation of individual water transfer mechanisms was used to elucidate the relative importance of several components of the hydro logic cycles of aspen and conifer, and determine which water transfer mechanisms have potential to cause differences in net water yield.

Adjacent aspen and conifer stands were monitored to determine snow accumulation and ablation (snow survey), soil moisture recharge (capacitance probes), snowpack sublimation (sublimation pan), transpiration period (thermal dissipation probes), and …

Quantifying Losses Of Understory Forage In Aspen Stands On The Dixie And Fishlake National Forests, Barton R. Stam

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The West has lost up to 60% of its historic aspen stands over the last century, probably as a result of the successional tendency of aspen to be replaced by coniferous species in the absence of periodic fires. One of several major impacts of this change is the loss of understory forage as conifer canopy cover increases. I measured understory biomass in aspen stands ranging from 0% to 81 % absolute conifer cover in the canopy and found that understory production declines exponentially as conifers replace aspen. I also did an economic analysis to determine the value of the forage …

Ecology Of Treeline Whitebark Pine (Pinus Albicaulis) Populations In Central Idaho: Successional Status, Recruitment, And Mortality, And A Spring Temperature Reconstruction From Whitebark Pine Tree Rings, Dana Lee Perkins

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research investigated the successional status of treeline whitebark pine (Pinus albicaulis) populations on 14 stands in central Idaho and used empirical statistical models to determine the principal factors affecting recruitment and mortality. The longest lived whitebark pines from four additional high-elevation sites were used to develop a tree-ring chronology to reconstruct over 1,000 years of average April-May temperature.

The assessment of stand structures using size-frequency distributions generally provides evidence that treeline whitebark pine populations are currently self-sustaining in areas of low to nonexistent incidence of white pine blister rust (Cronartium ribicola). However the presence of …

Forest Canopies: Form And Functional Relationships, Steven B. Jack

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Forest canopy structure is strongly influenced by stand density due to changing competitive interactions among the individual trees and in turn directly influences stemwood volume production. The structure and dynamics of forest canopies, particularly in relation to the production of stemwood, were examined in unmanaged, even-aged stands of two dissimilar tree species, Pinus contorta var. latifolia Engelm. and Abies lasiocarpa (Hook.) Nutt. The analysis of structure-production relationships was guided by a conceptual model which generated hypotheses and led to examination of assumptions incorporated in the model.

Mean crown dimensions were related to stand density through a negative exponential function for …

Modeling Forest Dynamics Based On Stand Level Resource Allocation, Geoffrey Candler Poole

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An ecologically based model of forest succession is presented. In the model, trees compete for a share of limited growth resources available from their environment. Competition is reflected by each tree's effect on the resource pool and is not explicitly modeled. Model parameters were fit to field data from subalpine forests of the Rocky Mountains. A technique for estimating model parameters from understory-tolerance rankings and silvical characteristics of each species is also presented. The model's output was consistent with our current understanding of forest dynamics. Emergent properties of the model also mimicked natural processes such as self-thinning, release, and maximum …

Using Computer Imaging To Assess Visual Impacts Of Forest Insect And Disease Pests, Daniel Rabin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Forest insect and disease pests alter the appearance of trees, thereby impacting visual resources. Because of the complexity of most forest landscapes, the degree of visual impact of pest-infested forest stands is difficult to quantify.

This paper describes a method of measuring visual impacts of pest-infested forest stands. Photographs of healthy Ponderosa pine trees were entered into a computer video-image-processing system. Using this system, images of trees were altered to simulate different degrees of infestation by limb rust, a forest pathogen.

The altered and unaltered images were shown to groups of observers who rated the scenes in terms of "scenic …

The Ecology Of Agropyron Inerme On Protected And Heavily Grazed Range Land In Cache Valley, Utah, Wallace R. Hanson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

During the past decade much attention has been attracted to the great range lands of the West. The inherently low productivity of these arid lands coupled with abnormal drought and constantly heavy use by livestock because of lack of grazing control, have caused these lands to become greatly depleted over most of the West. That the vegetation on most range land in the intermountain states is depleted appreciably is evident to the careful observer. Undoubtedly the vegetation of much of the range has decreased in quantity, but more serious in many cases is the decrease in quality. Valuable forage species …