Volume tables and taper equations for small diameter conifers

Graduation Date

2003

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Forestry, 2003

Committee Chair Name

Gerald Allen

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Forests and forestry--Tables, Conifers, Forests and forestry--Measurement, Humboldt State University -- Theses -- Forestry

Abstract

Although volume tables have been in existence for years and there are many available, there is very little empirically-based volume information for small diameter trees. For the current study, a total of 79 young ponderosa pine and 111 young white fir trees were selected from naturally regenerated stands and plantations in the McCloud Ranger District of the Shasta-Trinity National Forest. Tree diameters ranged from 1 to 13 inches (2.5 to 33 cm) at breast height and tree heights ranged from 7 to 81 feet (2.1 to 24.7 m). From field measurements, total cubic foot volume inside bark was calculated for each tree. Equations that estimate tree volume given height and diameter at breast height were constructed using weighted least squares regression techniques. In addition, crown ratio was examined for significance in predicting volume. Diameter and height were found to significantly influence volume while crown ratio was found to be insignificant. The model V = ß0 + ß1D2H was chosen and the results of weighted least squares regression showed that the data fit this model well. Statistical analysis showed that the simplest model was the most appropriate and was very precise, with R-squared values of 0.981 for the pines and 0.991 for the firs. From these equations, cubic foot volume tables were constructed. Kozak's variable-exponent taper function was analyzed with the same tree data using multiple regression and was found to fit the data closely. Upon analysis it was determined that this seven-factor equation could be simplified to a two-factor model with very little compromise in precision. Additionally, this shorter taper equation eliminated the problem of multicollinearity that was present in the seven-factor model, and was easier to interpret.

https://scholarworks.calstate.edu/concern/theses/1j92gb15f

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