Volume equations of Pinus brutia Ten. in Zawita Forest, Duhok Province, Iraq
Planning for forest management depends upon the forest dynamics, which includes integration of all forest disciplines and understanding of forest resource characteristics including its growth dynamics. The forest growth and yield modeling can provide valuable information about forestry, which...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/66825/1/FH%202016%2033%20IR.pdf |
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| Summary: | Planning for forest management depends upon the forest dynamics, which includes
integration of all forest disciplines and understanding of forest resource characteristics
including its growth dynamics. The forest growth and yield modeling can provide
valuable information about forestry, which can be used to determine harvest levels or
allowable cut and to analyze alternative stand treatments. The lack of technical
information on forests in the Zawita region is one of the main obstacles to the
development of growth and yield, environmental policy and forest evaluation
indicators. The Zawita plantation forest needs more information on yield models using
volume equations for P. brutia growing under the conditions of the Kurdistan Region
of Iraq which will contribute to providing valuable information in the planning and
sustainable management of the forest plantations in the region. Hence, this work has
been carried out to apply volume equations for P. brutia that can explicitly state the
relationship between tree volume and diameter and provide more information for the
development of more systematic forest management prescriptions at the Zawita region
in future. This study consists of four parts. For the first part, a large number of
mathematical models, which have been used by various authors in the development of
volume-tables and volume equation construction, were analyzed in searching for
suitable volume equations for P. brutia plantations. Overall, we have used eight
unweighted volume equations including two logarithmic transformed equations and
seven weighted forms of volume equations for volume data of a 25 – 30 year old P.
brutia plantation. In the second part, the study used the method of least squares for the
construction of volume equations, because the most common problem in volume table
construction has been the variation in tree forms or commonly referred to as
heteroscedasticity of residuals. This is because the larger tree volumes tend to deviate
from the regression line more than the smaller ones, and therefore the weighted least
squares was used to correct the heteroscedasticity in volume table construction. The
least squares method was used to fit the construction of volume equations for both
over bark and under bark volumes. The third part discussed the statistical method to
find the best-fit equation. A more suitable index for comparing regression equations has been devised by Furnival, which is based on the concept of maximum likelihood.
The index was used to determine the best-fit equation, in choosing the final equations
for both over and under bark equations. Finally, the study conducted validation to
compare the true volume calculated using Newton’s formula with the predicated
volume derived from the equation. The actual and estimated volume per hectare was
compared and tested using the t-test.
In conclusion, the study developed the following equations for estimating under bark
(VI) and over bark (VO) volume, equations:
VI = 0.0003378 * D1.21342 * H1.18863 , VO =0.0002722 * D 1.40425 * H1.06470, where VI
and VO are (merchantable tree volumes m3 up to 10 cm) breast height diameter (cm),
and H is the total log length (m). The equations were found to estimate merchantable
tree volumes. As usual, a test of applicability of these equations is needed if they are
to be applied elsewhere. |
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