Stem taper functions for white birch (<i>Betula platyphylla</i>) and costata birch (<i>Betula costata</i>) in the Xiaoxing’an Mountains, northeast China

Abstract White birch (Betula platyphylla Sukaczev) and costata Trautv.) are valuable hardwood tree species growing in northeast China. Several taper studies have analysed the countries harbouring boreal forests. However, this study presents an initial attempt to develop stem models using fixed- mixed-effects modelling for white Xiaoxing’an Mountains, Ten commonly used were evaluated by 228 destructively sampled trees of both comprising 4582 diameter height measurements. The performance these was tested predicting at any height, total volume merchantable (10 20 cm top diameters). We incorporated a second-order continuous-time error structure adjust inherent autocorrelation data. segmented model Clark best predicted or when upper 5.3 m available. When measurements not available, Kozak Max Burkhart superior other birch, respectively. After comparison, refitted as NLME model.