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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Prescribed Fire Effects on Tree Grades and Wounds on the Monongahela National Forest, WV

Sharpe, Caroline Marie 01 July 2022 (has links)
Species traits, including but not exclusive to bark thickness and texture, sprouting ability, and litter bulk density and chemistry, may be related to a stem's potential to withstand potential heating from wildland fire. Trees exhibiting similarities for these properties and others may be classified into two broad functional groups: pyrophytes and pyrophobes. To our knowledge, few research studies have been conducted to determine how prescribed fires may affect wood quality of merchantable tree species in the Appalachian Mountains. Understanding potential relationships between wounding and fire tolerance may assist prescribed fire managers as they seek to promote and expand the use of prescribed fire for management purposes. To investigate this issue, six locations on the Monongahela National Forest, West Virginia, that had been subjected to one or two mixed intensity and severity prescribed fires since 2012 were selected for stand inventory in 2021. Overstory trees within these burned locations and adjacent, unburned locations were measured and graded using variable radius sampling, and additional landscape features and physiographic factors, such as aspect, elevation, and slope percentage, were also recorded at each variable radius sampling location. The most common, commercially valuable deciduous species encountered were red maple (Acer rubrum) (17.5%), white oak (Quercus alba) (9.8%), chestnut oak (Quercus montana) (32.8%), and northern red oak (Quercus rubra) (39.9%). Using field measurements and tree grades, the total number and types of wounds, potential volume loss, charring, basal area, and diameters at breast height (DBH) were compared by species, burn status (burn or control), and the number of burns. Overall, A. rubrum and Q. rubra comprised 93% of the total trees exhibiting volume loss from wounds in the burned locations. However, total volume loss only constituted about 3% of the bottommost 4.9 m log. Trees in the burned locations experiencing volume loss differed significantly between species (p=0.0294) with Q. rubra constituting 60% of volume loss trees. In burned and control plots, A. rubrum was the most commonly wounded tree with 43.5% of trees having at least one wound. Cat face and oval wounds were the only wound types resulting in volume loss. Felling and milling stems identified in this study as having potential volume loss from any fire-influenced wounds would be valuable. Furthermore, assessing the potential impact of outer bark char resulting from prescribed fires would be desired to better understand if charring constitutes any potential internal damage to stems. Deploying a similar, field-scale experiment on areas with varying fire frequencies and intensities would be useful to determine how wood quality may be affected after several prescribed burns. / Master of Science / Prescribed fire is a cultural land management practice used historically and currently in many locations around the world. These burns have been and are currently conducted for many reasons, including wildlife habitat management, hazardous fuel reduction, and vegetation control. Trees have innate characteristics that increase potential resistance and resilience to fire damage, however, these characteristics can vary depending on tree species and tree age. These characteristics may include, but are not limited to, bark thickness and texture, litter chemistry, leaf shape, and a species' resprouting strategy. Prescribed fire is often used in conjunction with other forest management techniques (i.e. herbicides, thinning) in locations where timber value is a management priority, therefore it is important to understand how prescribed fire may affect the growth and quality of merchantable timber species. Few studies have focused on potential wood quality issues posed by the use of prescribed fire in the Appalachian Mountains. Determining if prescribed fires affect wood quality may provide land managers, in many locations, with information that may aid their selection of desired management practices and priorities. To help address this knowledge gap, a research study was designed and conducted to investigate these issues for the following merchantable timber species in six burned and adjacent, unburned locations of the Monongahela National Forest, West Virginia: red maple (Acer rubrum), white oak (Quercus alba), chestnut oak (Q. montana), and northern red oak (Q. rubra). The results show that one or two mixed intensity and severity prescribed fires, implemented since 2012, resulted in an overall volume loss of 3% from the bottommost 4.9 m log, therefore prescribed fire did not cause a significant reduction in total volume. Two main species, A. rubrum and Q. rubra, comprised 93% of the trees with wounds resulting in volume loss. However, Q. rubra alone constituted 60% of trees with volume loss wounds. The results also show that A. rubrum was the most commonly wounded tree with 43.5% having at least one wound. Additional research is warranted to more fully understand these dynamics, including sampling locations that have experienced more prescribed fires and fires with different intensities and milling wounded trees and charred trees located in burned locations.
22

A TIME SERIES ANALYSIS APPROACH TO TREE RING STANDARDIZATION (DENDROCHRONOLOGY, FORESTRY, DENDROCLIMATOLOGY, AUTOREGRESSIVE PROCESS).

COOK, EDWARD ROGER. January 1985 (has links)
The problem of standardizing closed-canopy forest ringwidth series is investigated. A biological model for the tree-ring standardization problem indicated that one class of non-climatic variance frequently responsible for standardization problems could be objectively minimized in theory. This is the variance caused by endogenous stand disturbances which create fluctuations in ringwidth series that are non-synchronous or out-of-phase when viewed across trees in a stand. A time series method based on the autoregressive process is developed which minimizes the timewise influence of endogenous disturbances in detrended ringwidth series. Signal-to-noise ratio (SNR) properties of this method are derived which indicate that autoregressive modelling and prewhitening of detrended ringwidth indices will result in a higher SNR when endogenous disturbances are present in the series. This enables the verification of the SNR theory and the error variance reduction property of the standardization method.
23

A taxonomic study of Dombeya Cav. (Sterculiaceae) in Africa with special reference to species delimitation

Seyani, J. H. January 1982 (has links)
No description available.
24

Stochastic tree models and probabilistic modelling of gene trees of given species networks

Zhu, Sha (Joe) January 2013 (has links)
In the pre-genomic era, the relationships among species and their evolutionary histories were often determined by examining the fossil records. In the genomic era, these relationships are identified by analysing the genetic data, which also enables us to take a close-up view of the differences between the individual samples. Nevertheless, these relationships are often described by a tree-like structure or a network. In this thesis, we investigate some of the models that are used to describe these relationships. This thesis can be divided into two main parts. The first part focuses on investigating the theoretical properties of several neutral tree models that are often considered in phylogenetics and population genetics studies, such as the Yule–Harding model, the proportional to distinguishable arrangements and the Kingman coalescent models. In comparison to the first part, the other half of the thesis is more computationally oriented: we focus on developing and implementing methods of calculating gene tree probabilities of given species networks, and simulating genealogies within species networks.
25

A comparative study of four Armillaria species

Davidson, A. J. January 1986 (has links)
No description available.
26

Environmental stress and the response of pinus caribaea Morelet cultured in vitro

Bedi, Seema January 1990 (has links)
No description available.
27

Chronic pollution injury to some tree species in response to SOsub(2) and NOsub(2) mixtures

Freer-Smith, P. H. January 1983 (has links)
No description available.
28

How to Hire A Tree Expert

Bradley, Lucy 10 1900 (has links)
3 pp. / Tree experts, known as arborists, provide a variety of services to help you care for the valuable investment you have made in your trees. This publication provides information about the type of services the arborists and tree workers provide, as well as the type of tree workers, the cost of hiring a tree worker and how to select a qualified tree worker.
29

Cooley Spruce Gall Adelgid in Northern Arizona above 6000 Foot Elevations

DeGomez, Tom 03 1900 (has links)
2 pp. / This publication provides information and describes Cooley spruce galls in Northern Arizona. Douglas-fir and spruce are alternate hosts for these galls. The life cycle of galls and their management/control methods are described in detail here.
30

Editorial

Swetnam, Thomas W. January 2001 (has links)
No description available.

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