Journal
IFOREST-BIOGEOSCIENCES AND FORESTRY
Volume 10, Issue -, Pages 567-575Publisher
SISEF-SOC ITALIANA SELVICOLTURA ECOL FORESTALE
DOI: 10.3832/ifor2114-010
Keywords
Quercus variabilis Blume; Dummy Variable; Box-Cox Transformation; Linear Mixed Effects Models; Compatible Taper-Volume Model
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Funding
- scientific and research base construction projects of Beijing Municipal Education Commission [SYSBL2009]
- forestry science promotion project of the State Forestry Bureau [2011-44]
- open fund project of Beijing Forestry University 985 advantage subject innovation platform [000-1108003]
- special fund project for forestry public service industry and research [201004021]
- China Scholarship Council
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Compatible taper and volume models were created for Quercus variabilis Blume (cork oak) forests in North China. 174 trees were felled to obtain stem analysis data. Linear mixed effects analyses were used in modelling. Firstly, a bark thickness model was built. Then diameter at breast height over bark (DBHob) for the inner layers of the 174 trees could be calculated, based on which a total volume model was built. The estimated volume and a specific parameter restriction were then substituted into a polynomial taper model, finally the taper model was fitted and compatible taper and volume models were obtained. Four sets of models based on different data sets were separately built and compared through coefficients of determination (R-2), root mean square error (RMSE), value of Akaike's information criterion (AIC), residuals plots and histograms of residuals. Models based on data of the analyzed stems without ramicorns and simultaneously with relative diameter under 1.5 were chosen as the most precise. Further testing of the chosen models using the jackknife method for the bark thickness and total volume models and a validation data set for the taper model verified that those models can be used to predict bark thickness, diameter at a specific point along the stem, merchantable volume and total stem volume of cork oak forests in North China within specific tree diameter at breast height and height ranges.
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