Variable-Exponent Taper Equation Based on Multilevel Nonlinear Mixed Effect for Chinese Fir in China
Open Access
- 23 January 2021
- Vol. 12 (2), 126
- https://doi.org/10.3390/f12020126
Abstract
A variable-exponent taper equation was developed for Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) trees grown in southern China. Thirty taper equations from different groups of models (single, segmented, or variable-exponent taper equation) were compared to find the excellent basic model with S-plus software. The lowest Akaike information criteria (AIC), Bayesian information criteria (BIC), and -2loglikelihood (-2LL) was chosen to determine the best combination of random parameters. Single taper models were found having the lowest precision, and the variable-exponent taper equations had higher precision than the segmented taper equations. Four variable-exponent taper models that developed by Zeng and Liao, Bi, Kozak, Sharma, and Zhang respectively, were selected as basic model and had no difference in fit statistics between them. Compared with the model without seldom parameter, the nonlinear mixed-effects (NLME) model improves the fitting performance. The plot-level NLME model was found not to remove the residual autocorrelation. The tree-level and two-level NLME model had better simulation accuracy than the plot-level NLME model, and there were no significant differences between the tree-level and two-level NLME model. Variable-exponent taper model developed by Kozak showed the best performance while considering two-level or tree-level NLME model, and produced better predictions for medium stems compared to lower and upper stems.Keywords
This publication has 32 references indexed in Scilit:
- Variable-exponent taper equations for jack pine, black spruce, and balsam fir in eastern CanadaForest Ecology and Management, 2004
- My last words on taper equationsThe Forestry Chronicle, 2004
- Dimensionally compatible volume and taper equationsCanadian Journal of Forest Research, 2001
- Taper equations for Eucalyptus pilularis and Eucalyptus grandis for the north coast in New South Wales, AustraliaForest Ecology and Management, 1999
- Variable-form taper functions for four Alberta tree speciesCanadian Journal of Forest Research, 1992
- A variable-exponent taper equationCanadian Journal of Forest Research, 1988
- A Simple, Variable Form Volume Estimation SystemThe Forestry Chronicle, 1985
- The whole-bole system: a conditioned dual-equation system for precise prediction of tree profilesCanadian Journal of Forest Research, 1977
- A simple bole modelThe Forestry Chronicle, 1973
- Taper Functions and their Application in Forest InventoryThe Forestry Chronicle, 1969