By: Abwage W. D.; Ogana F. N.;
Abstract:
The main aim of this study was to assess the effect of plot dimension on Weibull parameters estimation in describing
diameter distribution of Eucalyptus camaldulensis Dehn plantation, Afaka Forest Reserve, Kaduna State, Nigeria.
Information on diameter distribution should be obtained from the rightful data analytical tool which will not mislead
the manager in decision making. As such, plot dimension should be varied to accommodate a minimum of 60 trees
which proves to have a better fit and prediction with Weibull parameters estimated through Maximum Likelihood.
The parameters of Weibull were estimated from three dimensions (20 x 20m, 30 x 30m and 40 x 40m) using
Maximum likelihood (MLEW), Traditional method of moment (MMW), Moment incorporating skewness (MISW)
and percentile. (PW). The data used for this study came from temporary sample plots (TSP). The Weibull parameters
were estimated from the three plots dimensions independently through the above parameters estimation method. The
three plots dimensions were compared vis-a-vis the parameter estimation method. The comparison was based on
Kolmogorov-Sminov (K-S), mean square error (MSE), mean absolute error (MAE) and bias. Based on plots
dimension and parameter estimation method, plot size 40 x 40m and MLE proves to have better fitting and prediction.
Hence, a larger sample size with MLE appears to be the most suitable for Weibull parameters fitting and diameter
prediction study.
Keywords: Diameter distribution prediction; Weibull distribution function; parameter estimation methods; plot dimension;
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