角规三维点抽样估测林分蓄积的形点法冠下削度方程

在角规点上,用形点法测定林分蓄积时,需要直接测定林分的高H.然而在现实林分中,树冠重叠,通视较差,测定林分高H颇为困难.为此,该文运用形点法理论对林分冠下树干的形状结构进行解析,发现采用角规三维点抽样直接测定林分冠下的辅助高Hb及其断面积Gb、近似形点高Ha及其断面积Ga和胸高断面积G后,推导其间的相互关系,能自动生成林分形状指数R和林分高H,于是提出了形点法林分冠下削度方程,方程中不含任何经验参数.所以在测定林分蓄积M时,能避开测定林分高H的通视困难,具有较强的通用性、实用性和准确度,并对估计林分材种材积提供实用的理论依据,是对角规测树理论由二维空间向三维空间发展的重要突破.

Under-crown taper equation of form point method in combination with three dimensional point sampling with angle gauge for stand volume estimation.

Stand height(H) has to be directly measured to estimate stand volume with form point method,which,however,is not easily measured because of poor visibility.Theory of point sampling was applied to analyze stand under-crown stem form and structure.With parameters as G(basal area at DBH),H_a(height at the approximate form point),G_a(basal area at the approximate form point),H_b(height at the accessorial point) and G_b(basal area at the accessorial point) directly measured with the three dimensional point sampling with angle gauge,their interrelation was deduced.With automatic development of stand form exponent R and height H,under-crown taper equation of form point method was proposed without any experiential parameters included.This equation has strong applicability and accuracy for stand volume estimation,which marked the breakthrough from two-dimensional sampling to three dimensions in mensuration theory with angle gauge.