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

Amna Hussain,Muhammad Khurram Shahzad,Harold E Burkhart,Lichun Jiang

doi:10.1093/forestry/cpab014

Amna Hussain, Muhammad Khurram Shahzad + Show 2 more

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https://doi.org/10.1093/forestry/cpab014

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Journal: Forestry	Publication Date: Mar 27, 2021
Citations: 8	License type: CC BY 4.0

Affiliation: Northeast Forestry University, Virginia Tech

Abstract

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

Highlights

Forest area in China accounts for 220 million ha with a standing volume of 17.56 billion m3, as per the latest National Forest Inventory (NFI–9)
White birch (Betula platyphylla Sukaczev) and costata birch (Betula costata Trautv.) are valuable hardwood tree species growing in northeast China
The specific objectives of this study were to: (1) evaluate well-known segmented and variable form taper models using fixed-effects and select the best model for diameter and volume prediction of white birch and costata birch and (2) develop treespecific mixed-effects models based on the best taper model

Summary

Introduction

Forest area in China accounts for 220 million ha with a standing volume of 17.56 billion m3, as per the latest National Forest Inventory (NFI–9). State Forestry Administration aims to maintain the forest cover at over 26 per cent by the year 2050 to bridge the supply and demand gap and achieve a sound cycle of ecological conditions (Xu et al, 2019). White birch (Betula platyphylla Sukaczev) and Korean/costata birch (Betula costata Trautv.) are major valuable tree species of China covering an area of 10.38 million ha, with a total volume of 923 million m3 (Xu et al, 2019). Costata birch provides the raw material for pulp and fibre-based products. They play an important role in maintaining the ecological balance of the natural broad-leaved secondary forest in Northeast China (Wang et al, 2018a; Zhao et al, 2019)

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