ABSTRACT

Estimation of stem volume is needed to determine timber yield and forest carbon, but equations to estimate volume from easily assessed inventory measures are lacking for hardwood plantation species in the subtropics. We assessed the merits of three volume equations that combine measurements of tree diameter at breast height (DBH) and total tree height for five hardwood plantation taxa (Corymbia citriodora subsp. variegata, Corymbia hybrids, Eucalyptus cloeziana, E. longirostrata and E. dunnii). Goodness-of-fit statistics indicated that model 1 (comprehensive combined variable equation) and model 2 (the Schumacher and Hall equation) fitted the data well (e.g. adjusted R² > 98). Analysis of bias in different diameter classes indicated that these models did not show any systematic bias patterns with tree size. Model 3 (combined variable volume equation) is the least desirable as it showed evidence of overestimation of volume for larger trees in some taxa. Models 1 and 2 provide a useful initial set of volume equations for five potentially important hardwood plantation species in subtropical Queensland. These equations are based on stems with a DBH range of 5−30 cm and hence there is a need to collect data for larger stems (>30 cm DBH) as existing plantations mature.

摘要

需要估计茎的体积来确定木材产量和森林碳，但是对于亚热带地区的硬木人工林物种，缺乏根据易于评估的清单措施估计体积的方程。我们评估了三个体积方程的优点，这些方程结合了五种硬木人工林分类群（Corymbia citriodora subsp. variegata、Corymbia hybrids、Eucalyptus cloeziana、E. longirostrata和E. dunnii）的胸高树径 (DBH) 和总树高测量值的优点. 拟合优度统计表明模型 1（综合组合变量方程）和模型 2（舒马赫和霍尔方程）与数据拟合良好（例如调整后的R ² > 98）。对不同直径等级的偏差分析表明，这些模型没有显示任何与树木大小有关的系统偏差模式。模型 3（组合可变体积方程）是最不理想的，因为它表明某些分类群中较大树木的体积被高估了。模型 1 和 2 为昆士兰亚热带地区的五种可能重要的硬木人工林树种提供了一组有用的初始体积方程。这些方程基于 DBH 范围为 5-30 cm 的茎，因此随着现有种植园的成熟，需要收集更大茎 (>30 cm DBH) 的数据。