Red spruce (Picea rubens Sarg.) is a commercially and ecologically important conifer species that primarily exists at northern latitudes of eastern North America. During the last glaciation, its range extended down the Appalachian Mountain chain into North Carolina and Tennessee. Since the planet warmed over the subsequent millennia, only small, sky-island populations remain at the highest peaks of the southern Appalachians where their habitat continues to be threatened by a warming climate. While they have been recognized for the rare wildlife habitat they provide in the region, these populations remain understudied. This thesis aimed to provide additional quantitative methods for managing red spruce stands through regionally fitted stem taper equations and to examine differences in stem form between the northern and southern populations of red spruce.
In Chapter 1, five stem taper equations were evaluated for their ability to predict upper stem diameters and total volume in southern Appalachian red spruce: a simple linear, a quadratic polynomial, a segmented, a variable exponent, and a geometric model. Based on past studies and our results, we found that the best equations to use were the variable exponent and segmented polynomial models. Users should consider their own objectives and practical limitations in choosing which equation to use. In Chapter 2, we examined differences in stem form using three methods: a sectional rate of change in diameter, a sectional form class ratio, and a region variable added to two taper equations. The results were mixed, with the rates of change showing significant differences (p<0.05), but the form class ratios showing a mix of significant and insignificant differences. The two equations also had contrasting significance results. This made it unclear whether there were significant differences in stem form between the two populations but supported the idea that localized taper equations would provide the best results. / Master of Science / Red spruce (Picea rubens Sarg.) is a conifer native to eastern North America. It primarily exists in cold, moist climates found in the northeastern US and eastern Canada. Additionally, remnant populations of red spruce exist along the highest peaks of the Appalachian Mountains southward into North Carolina and Tennessee. These trees have been separated from northern red spruce populations for thousands of years and subjected to different growing conditions at high elevations that may have affected their stem characteristics.
Stem taper is the rate at which the diameter of a tree's stem changes from the ground to the tip. Many equations have been developed to estimate diameters throughout the stem using simple measurements like total height and diameter at breast height (1.37 m or 4.5 ft). These equations can be used to estimate diameters, heights, and volumes of trees which is helpful for valuing trees for wood production, carbon accounting, or wildlife habitat. Stem taper can vary among species and within a species, so tailoring equations to local populations is important for obtaining the most accurate estimates.
Currently, there are no known taper equations fitted specifically for these red spruce trees in the southern Appalachians. This thesis aimed to develop stem taper equations specific to this population of trees and to analyze whether the stem forms of southern red spruce trees differed from their northern counterparts. The results showed that there is evidence both for and against the hypothesis that these populations have different stem forms, and further research is necessary to confirm differences. We also showed that a variable exponent equation and a segmented polynomial equation provided the most accurate estimates of diameter and volume for the southern spruce populations.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115876 |
| Date | 24 May 2023 |
| Creators | Morrone, Steven |
| Contributors | Forest Resources and Environmental Conservation, Green, Patrick Corey, Carter, David Robert James, Radtke, Philip J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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