Abstract:
Eucalyptus camaldulensis tree species is one of the most important tree species which have
socio-economic and environmental values. With the increasing demand for timber production,
the correct and precise assessment of tree stand stock are essential for decision-making and for
ensuring sustainable forest management. However, in Mecha district, there is a limited scientific
information on site specific form factor, stem volume and height prediction regression model for
this species. Therefore, the objectives of this study were determination of species-specific form
factor, and development of tree height and stem volume models for six years old plantation of E.
camaldulensis, in Mecha district North West Ethiopia. For this study, first the sample plantation
site was purposively selected. Then, four transect lines were randomly laid out in the plantation,
and within each transect line, four circular plots having 5.64 meters radius
were systematically established. At each plot, all trees DBH were measured, and each tree
stratified based on DBH class. From each diameter class, sample trees were proportionally
selected. Therefore, a total of 80 sample trees were used for form factor determination and
model development. For the computation of stem real volume, stem of each tree was cross
sectioned with a section length of 0.5 meters intervals and its diameter and length were
measured. The collected data was analyzed by linear and nonlinear regression using MS-excel
and IBM SPSS 20 software. Then, descriptive and inferential statistical analysis were conducted.
The model fitness were assessed using Coefficient determination (R²), Root Mean Square Error
(RMSE), Mean Absolute Error (MAE) and Mean Absolute Percent Error (MAPE) and validation
assessed using paired t-test. The result indicates that the mean value of real form factor was
0.485. The trend of form factor across diameter classes decreased from lower diameter to higher
diameter classes. The finding of tree height prediction model showed that the best fit model for
predicting tree height was found to be H=a+bDBH+cDBH
2
. This model was found to be suitable
and recommended for predicting total tree height of a six-year-old plantation of E.
camaldulensis in the study area. The DBH and Height accurately explained the stem volume
with the form- V=a+bDBH+cDBH
2
*H and it was the best model and can be applied for
estimating stem volume of young E. camaldulensis plantation in the Mecha district, Amhara
region, Ethiopia.
