伐倒木区分求积的Excel VBA算法与程序实现

为了快速完成区分求积计算过程,本文在总结中央断面区分求积式和平均断面区分求积式的基础上,提出了区分求积的Excel VBA算法:第一,根据倒木全长和区分段长度,确定区分段段数,并建立区分段序号与区分段中央直径(或底端直径)的位置序号之间的数学关系式;第二,采用中央断面近似求积式(或平均断面近似求积式)计算每个区分段的材积并求和;第三,各区分段材积之和加上梢头材积就得到伐倒木材积。根据算法,最终编写了伐倒木区分求积Excel VBA程序代码。     

用图解法直接确定树干立方材积

对于树干材积的测定,传统的比较精确的方法是中央断面积区分求积法。此法是将树干区为一米或二米长的等长区分段,分别测定各段的中央直径,梢底直径和梢头长度,做详细记录。然后以计算或查表的方法求算各段和梢头材积进行合计,即为树干材积。该法测算手续比较烦杂,而对业务不够熟习者一但搞错一个区分段中央直径位置,材积计算就会出现大错。笔者参考国外有关资料,研制了一种适合于我国木材度量单位,     

吉尼(Gini)系数在评定立木干形的应用

论述用立木树干按树高相对区分求得各相对区分段材积及其占总材积比重 ,然后作一次累加生成数列 ,用幂函数拟合 Lorenz曲线 ,通过积分求积 ,导出 Gini系数 ,以此作为评定干形饱满度的指标     

关于同株树干中央断面区分求积精度计算公式的商榷

中央断面区分求积精度计算公式P_n=(P_1/n~2)有值得商榷的地方。按照本文的观点,公式应为P_n=(P_1/n),并认为材积误差率是随区分段数的增加而减少,且随树干削度的增加而增加。     

关于区分求积精度计算公式的商榷

北京林学院主编的《测树学》教材中,在第一章第四节就区分求积的误差问题,周沛村同志导出了如下表达式:P_n=P_1/n~2(式中n为区分段数)。安徽农学院章平澜同志对此式提出了异议。我想发表一点看法,与上述两同志商榷。首先,我认为区分求积与不区分求积相比,其前提是在对同株树干,用同样公式进行求积,主要讨论随着区分段数的增加其精度的变化。由于树干形状多变,不是也不可能把     

谈《立木树干材积与材种出材率表》的修订

用分段取函数、建立回归方程的方法,将原省森工局颁发的《立木树干材积与材种出材率表》中的以8cm为始测径阶、4cm为一进阶的立木树干材积修订为6cm为始测径阶、2cm为一进阶的树干材积,同时以样条函数和数值逼近法解决2cm为进阶的各材种出材率。     

用树干平均直径计算去皮材积的方法

本文提出只要在树干上测量其区分段求得其平均直径处的去皮直径,就能用圆柱体求积式计算出树干去皮材积。该法不但能够减少外业工作量,而且计算简便,精度高。同时也可用平均直径直接计算出树皮率和胸高形数。     

一种新的干形表示方法—相对干率的研究

在前人研究的基础上,笔者提出用相对干率来表示干形,通过相对干率可以把各种各样的现实树干转化为统一标准的圆柱体,并能够排列在一张平面图上实现直观图示。本文应用相对干率分析了长白山8个主要阔叶树种和同一树种不同树高阶段的干形差异及树干材积结构的变化。一、相对干率按照Hohenadl的5区分段等相对长区分求积法,令树干长L=1,从梢头开始取相对等间隔0.2L,在树干的0.1L,0.3L,0.5L,0.7L和0.9L处测定直径d_(0.1),d_(0.3),d_(0.5),d_(0.7)和d_(0.9)。若将各区分段材积V_i与树干总材积V之比定义为相对干率,则相对干率序列X_i即为:     

CASIO fx-4500P/4800P计算器在伐倒木区分求积中的应用

对CASIO fx-4500P/4800P 型计算器在伐倒木区分求积中的应用进行了阐述.给出了按不同的区分方法和求积算法计算树干材积的方法、程序及相应的材积误差率.列出了程序流程及清单,并对其使用作了说明.     

拟赤杨树干材积及鲜重按相对区分段分布格局

全文对不同起源不同树龄瓜赤杨将其树干按高划分１０个相对区分段，探索材积与鲜重按相对区分段的分布格局。     

四川柏木材种出材率表的编制

在总结国外编制材种出材率表、商品材积表的基础上,应用三次样条函数建立相对干曲线模型。并对干形进行分类,进而转化为绝对干曲线模型,结合二元材积表进行造材和编表,该方法克服了削度方程和材积比方程以平均干形建模造成的误差,同时,和材积表很好地结合起来,使数表配套。     

A flexible stem taper and volume prediction method based on mixed-effects B-spline regression

Modelling stem taper and volume is crucial in many forest management and planning systems. Taper models are used for diameter prediction at any location along the stem of a sample tree. Furthermore, taper models are flexible means to provide information on the stem volume and assortment structure of a forest stand or other management units. Usually, taper functions are mean functions of multiple linear or nonlinear regression models with diameter at breast height and tree height as predictor variables. In large-scale inventories, an upper diameter is often considered as an additional predictor variable to improve the reliability of taper and volume predictions. Most studies on stem taper focus on accurately modelling the mean function; the error structure of the regression model is neglected or treated as secondary. We present a semi-parametric linear mixed model where the population mean diameter at an arbitrary stem location is a smooth function of relative height. Observed tree-individual diameter deviations from the population mean are assumed to be realizations of a smooth Gaussian process with the covariance depending on the sampled diameter locations. In addition to the smooth random deviation from the population average, we consider independent zero mean residual errors in order to describe the deviations of the observed diameter measurements from the tree-individual smooth stem taper. The smooth model components are approximated by cubic spline functions with a B-spline basis and a small number of knots. The B-spline coefficients of the population mean function are treated as fixed effects, whereas coefficients of the smooth tree-individual deviation are modelled as random effects with zero mean and a symmetric positive definite covariance matrix. The taper of a tree is predicted using an arbitrary number of diameter and corresponding height measurements at arbitrary positions along the stem to calibrate the tree-individual random deviation from the population mean estimated by the fixed effects. This allows a flexible application of the method in practice. Volume predictions are calculated as the integral over cross-sectional areas estimated from the calibrated taper curve. Approximate estimators for the mean squared errors of volume estimates are provided. If the tree height is estimated or measured with error, we use the “law of total expectation and variance” to derive approximate diameter and volume predictions with associated confidence and prediction intervals. All methods presented in this study are implemented in the R-package TapeR.     

Efficiency of alternative forest inventory methods in partially harvested stands

Forest inventory is vital to all aspects of forest management and inventory methods can vary greatly in their accuracy, precision, efficiency and cost. In Maine, much of the forestland base has been managed using partial harvesting methods over the past two decades. These partial harvesting methods generally produce highly heterogeneous stand structures and composition. Consequently, it is currently unclear which inventory methods are best given the distinct spatial and structural heterogeneity that is created. We compared efficiency and stand-level inventory estimates using horizontal point, fixed area and horizontal line sampling measurement methods in 16 partially harvested stands across northern and central Maine. Some stand-level variables were sensitive to measurement method (e.g., volume, quadratic mean diameter and small stem density and basal area), while others were less sensitive (e.g., overall basal area and stem density). Efficiency, defined as a combination of precision of volume estimates and measurement time, varied among measurement methods at lower stand basal area values but was similar at higher basal area, with the exception of the fixed area method. Overall, horizontal line sampling proved to be a viable method in post-partial harvest stand conditions. Our results illustrate the trade-offs between precision and time costs involved in several measurement methods under a range of heterogeneous stand conditions.     

利用三维激光扫描系统测量立木材积的方法

介绍三维激光扫描系统的组成及工作原理,并采用该方法对立木进行扫描,测量立木材积。与伐倒木实测数据进行对比,可以看出扫描数据完全能满足林业测量的精度要求,其扫描获得的立木材积数据完全可以替代传统方法测算的立木材积数据,使用立木模型建立材积表不再需要实地大量伐木,节省大量人力、物力及财力。应用三维激光扫描技术进行立木材积测定能较好的避免传统测定方法的不足,在未来的林业数字化测量中有广阔的应用前景。     

三次平滑样条函数在冷杉干曲线预测上的应用

基于吉林省汪清林业局金沟岭林场95株冷杉天然林解析木(Abies nephrolepis)的胸径、树高及从地面起至树梢的11个高度处的直径数据,利用三次平滑样条函数结合线性预测理论得出冷杉的干曲线。最后分析模型的算术误差和相对误差的均值、标准差和均方误差。分析结果表明:预测得出的干曲线能够很好地反映冷杉干形的生长变化,预测材积与实际材积非常接近。     

样木解析法及其在材积表编制中的应用研究

提出了一种材积表编制样本资料收集的新方法———样木解析法。即在标准地中采用随机或机械抽样方法选取样木,进行树干解析,获得样木生长过程;通过建立树皮系数与树皮率回归模型,将样木解析后的各龄阶去皮直径和去皮材积转化为带皮直径和带皮材积,一株样木可获得龄阶数个编表样本。经四川农业大学实习林场楠木一元材积表、二元材积表编制实践,有减少编表样本收集工作量、消耗林木少的优点,且能达到精度要求,同时,也为珍稀树种材积表编制样本资料收集提供了新的方法。     

Stem Volume Equations for Valuable Timber Species in Mozambique

Development of stem volume for umbrella-shaped crown trees remains a big challenge for efficient use of forest resources in Mozambique. In this study, species-specific stem volume equations were developed for the first time for three of the most important timber species in Mozambique: Afzelia quanzensis Welw. (Chanfuta), Millettia stuhlmannii Taub. (Jambire), and Pterocarpus angolensis D.C. (Umbila). The study was carried out at three locations in Mozambique: Inhaminga, Mavume, and Tome covering 58 trees from which, 24 of Chanfuta, 15 of Jambire, and 19 of Umbila. The volume of the sampled stem sections (logs) was calculated using Smalian’s formula, where stem volume total was obtained through the sum of the respective defined sections. Using a nonlinear procedure, different volume models were tested for each tree species independently. The coefficient of the determination of the tested equations in the tree species ranged from .90 to .95, making the equations potential candidate models for the stem volume equations object of the study. Based on statistical parameters analysis, the best fit nonliner power equation was Equation 2 with the lowest AICc and lowest average absolute bias. The stem volume for the studied species is better explained by models including both diameter and height as explanatory variables.     

An improved technique for non-destructive measurement of the stem volume of standing wood

An improved technique, cheaper and less time-consuming, to measure standing wood volume by using an electronic theodolite was tested, by which greater information from the forest could be acquired accurately and non-destructively. This was achieved by recording the diameter at breast height and ground-level diameter of a tree as well as the included angle between the electronic theodolite and the left and right tangents of the stem at any point. The standing wood volume then was computed precisely by section. In addition, the factors that influence the precision of the method (observable distance and number of segments) were also analysed. In the study, 175 Larix gmelinii (Rupr.) Kuzen. trees and 190 Populus tomentosa Carrière trees chosen randomly for sampling were measured with the electronic theodolite, and then were cut down for measurement of the average cross-section volume. Based on the data acquired from 100 sample trees, a standard volume table was compiled, and then the data for the remaining random 10 sample trees in each group were selected for a comparison test. The results indicated that the optimal distance for indirect observation should be as high as the sample tree, and the optimal visual distinguished section was about 2?m. The correlation coefficient between the value measured non-destructively and the value of the felled trees of L. gmelinii was 0.97, with an average relative error of 1.62%. With regard to P. tomentosa, the correlation coefficient between the two values obtained by the two methods was 0.905 with an average relative error of 8.40%. It was concluded that the standard volume model based on the non-destructive measurement technique meets the requirements for precision in forest surveys. The precision of the standard volume model for L. gmelinii (a coniferous tree) was superior to that of the model for P. tomentosa (a broad-leaved tree). The electronic theodolite method provides an alternative technique for measuring trees without destructive sampling and is widely applicable for forest surveys.     

Modelling the economically viable wood in the crown of European beech trees

Long-term forest development programs in Germany aim on an increase of close-to-nature broadleaf forest stands. This means that the economic importance of European beech is expected to increase. The economic potential of a tree basically consists of the stem as well as the economically viable wood volume in the crown. Due to the high morphological variability of European beech crowns, taper models are often not satisfactory for predicting the economically viable wood volume arising from crowns. Prediction models with a higher precision are recently still lacking. Aim of this study is thus the development of prediction model for the economically viable crown wood volume of European beech trees.We determined the distribution of the wood volume in the crown over the branch diameters using the multistage ‘randomized branch sampling’ method (RBS). The tree-specific wood volume distribution on the branch diameters were used to cluster all sampled trees into 3 groups. Additionally, we developed a method able to distinguish between economically viable and unviable crown branches. Basing on the RBS measurements as well as revenues and processing costs, we modeled the economically viable wood volume from the crown for each tree. To calculate the wood volume under bark, we parameterized a bark thickness function from disk samples of the trees.We showed that the European beech crowns could be clustered into 3 groups differing in their wood volume distribution. The economically viable wood volume in the crown significantly depended on this grouping parameter as well as diameter at breast height (DBH). By contrast, the total amount of wood in the crown only depended on DBH. The differing viable wood volumes in the crowns were thus explained by different wood distributions and not by differing total crown wood volume. To make the results applicable in practice forestry, the modelling results were used to develop a regression formula able to predict the economically viable wood volume in the crown depending on the DBH and the crown type. As the crown type can also be predicted via measurable tree covariates, the regression model of the viable wood volume in the crown can be used as a support tool for the management of European beech stands. Sensitivity analysis quantifies how harvest revenues and costs translate into different viable tree volume.     

云南省云杉立木生物量模型研建

以云南云杉为研究对象,对云杉地上生物量和地下生物量模型进行研建。建立云杉地上总生物量、树干、树冠、干材、干皮、树枝、树叶独立模型与材积相容模型,采用分级联合控制和度量误差模型方法,建立地上总生物量和所有分量相容的立木生物量模型,建立根茎比模型对云杉地下生物量进行估计。结果表明：建立的云杉地上总生物量、树干、干材生物量二元模型预估精度均达95％以上,干皮生物量模型预估精度达94％以上,树冠、树叶、树枝生物量的预估精度均在92％以上,地下生物量模型预估精度在88％以上;所建立的模型可以用于云杉生物量的估计。