Stem taper functions for Betula platyphylla in the Daxing’an Mountains, northeast China

• Published in: Journal of forestry research 2021-04, Vol.32 (2), p.529-541
• Main Authors: Shahzad, Muhammad Khurram, Hussain, Amna, Burkhart, Harold E., Li, Fengri, Jiang, Lichun
• Format: Article
• Language: English
• Subjects: Analysis; Betula platyphylla; Biomedical and Life Sciences; Diameters; Environmental protection; Forest management; Forestry; Life Sciences; Mountains; Original Paper; Stems; Sustainable forestry; Tapering
• ISSN: 1007-662X; 1993-0607
• DOI: 10.1007/s11676-020-01152-4

Accurate prediction of stem diameter is an important prerequisite of forest management. In this study, an appropriate stem taper function was developed for upper stem diameter estimation of white birch ( Betula platyphylla Sukaczev) in ten sub-regions of the Daxing’an Mountains, northeast China. Three commonly used taper functions were assessed using a diameter and height dataset comprising 1344 trees. A first-order continuous-time error structure accounted for the inherent autocorrelation. The segmented model of Max and Burkhart (For Sci 22:283–289, 1976. https://doi.org/10.1093/forestscience/22.3.283 ) and the variable exponent taper function of Kozak (For Chron 80:507–515, 2004. https://doi.org/10.5558/tfc80507-4 ) described the data accurately. Owing to its lower multicollinearity, the Max and Burkhart (1976) model is recommended for diameter estimation at specific heights along the stem for the ten sub-regions. After comparison, the Max and Burkhart (1976) model was refitted using nonlinear mixed-effects techniques. Mixed-effects models would be used only when additional upper stem diameter measurements are available for calibration. Differences in region-specific taper functions were indicated by the method of the non-linear extra sum of squares. Therefore, the particular taper function should be adjusted accordingly for each sub-region in the Daxing’an Mountains.