Abstract
Background: Effective forest management and planning often requires information about the distribution of volume by size and product classes. Size-class models describe the diameter distribution and provide information by diameter class, such as the number of trees, basal area, and volume per unit of area. A successful diameter-distribution model requires high flexibility yet robust prediction of its parameters. To our knowledge, there are no studies regarding diameter distribution models for Eucalyptus hybrids in Indonesia. Therefore, the aim of this study was to compare different recovery methods for predicting parameters of the 3-parameter Weibull distribution for characterising diameter distributions of Eucalyptus hybrid clone plantations, on Sumatera Island of Indonesia. Methods: The parameter recovery approach was proposed to be compatible with stand-average growth and yield models developed based on the same data. Three approaches where compared: moment-based recovery, percentile-based prediction and hybrid methods. The ultimate goal was to recover Weibull parameters from future stand attributes, which were predicted from current stand attributes using regression models. Results: In this study, the moment method was found to give the overall lowest mean error-index and Kolmogorov– Smirnov (KS) statistic, followed by the hybrid and percentile methods. The moment-based method better fit long tails on both sides of the distribution and exhibited slightly greater flexibility in describing plots with larger variance than the other methods. Conclusions: The Weibull approach appeared relatively robust in determining diameter distributions of Eucalyptus hybrid clone plantation in Indonesia, yet some refinements may be necessary to characterize more complex distributions.
Highlights
Effective forest management and planning often requires information about the distribution of volume by size and product classes (Burkhart & Tomé 2012)
Based on the likelihood ratio test, the best random-effects models included all coefficients as random effects of clone and site class within the clone (Table 2)
Moments are the preferred method in growth and yield models because they ensure numeric compatibility and generally require fewer equations (Weiskittel et al 2011)
Summary
Effective forest management and planning often requires information about the distribution of volume by size and product classes (Burkhart & Tomé 2012). Size-class and individual-tree models are required for predicting distributions of multiple products (Weiskittel et al 2011), since they provide detailed yield estimates by size (De Miguel et al 2010). Size-class models predict diameter distributions and provide estimates of forest attributes (such as the number of trees, basal area, and volume per unit area) by diameter class (Poudel & Cao 2013). Effective forest management and planning often requires information about the distribution of volume by size and product classes. Size-class models describe the diameter distribution and provide information by diameter class, such as the number of trees, basal area, and volume per unit of area. The aim of this study was to compare different recovery methods for predicting parameters of the 3-parameter Weibull distribution for characterising diameter distributions of Eucalyptus hybrid clone plantations, on Sumatera Island of Indonesia
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