采伐迹地上经整地营造的火炬松的材积方程

利用在南部广泛区域的采伐迹地上经整地营造的火炬松树干解析数据,建立了总材积和商品用材部分的材积方程。这里提出了用以预测注意高度式小头直径处的总材积和商品材部分的材积方程。树干的尖削度与商品材材积方程之间的关系使得对小头直径和树高的预测成为可能。     

吉林省蒙古栎削度方程与材种出材率表研究

利用在吉林省各县(市、区)所采集3 157株蒙古栎编表、验表样木数据,运用削度方程计算立木材积和材种出材率表,结果表明:运用削度方程可以灵活地反映树干上任意部位直径、既定直径处材长、材积、出材率、树干上任意分段材积和全树干材积;同时根据林分树高差异调整树高式参数,编制的材种出材率表精度高、适用性强,更符合林分中林木生长实际状况     

理论造材:削度方程和出材率表的编制

本文提出了计算机理论造材仅根据削度方程和单株带,去皮胸径的转换关系式两个模型,可不必由削度方程推导材长方程和材积比方程。比相关指数,均方程为指标,结合残差图分析,选择了杉木、落叶松的削度方程;结合标准树高曲线,是可仅根据优势高为任一具体林分编制（一元）单株出材率表（特称之为自动调整出材率表）。     

一个简单的可变干形材积估算系统

以一种单的可变干形树干尖削度曲线为基础,建立了一个给出树干纵剖面(树干上部带皮直径),总林木材积、商品材材积(从地面到某树高限或直径限)的材积估算系统。这一树干尖削度曲线由指示圆锥干形和抛物线干形的系数值所确定。对于给定的树高,小径木确定为抛物线干形,大径木确定为圆锥干形。林木在这一干形系列中的位置由其总树高与胸径的比值来确定。利用大湖区北部美国赤松、斑克松、白云杉的树干解析资料,对本材积估算系统的性能进行了评价。     

根据以大头直径为变量的商用材与总材积的比率模型推导总材积公式

人们常用预报商用材与总材积之比的模型来推导出标准总材积公式。这是根据Clutter(1980)以梢端直径为变量的商用材公式导出尖削度公式的方法扩展而来的。利用导出的材积公式展开的尖削度曲线必须通过伐根高的直径。推导出的材积公式连同Clutter(1980)的结果都是总材积与由商用材比总材积的比率模型这个特定形式导出的尖削度公式兼容系统的一部分。     

苍梧县杉木削度方程与材积比方程研究

在苍梧县共青林场等集体林场的伐区,随机量测样木548株,年龄为20～21年,直径分布6～26cm,树高6～16m,按2m区分段,量测各段中央处的带皮直径、去皮直径,并现场造材,记录不同材种的出材率。并选择模型7为最适宜削度方程,方程11为最适宜材积方程,确定了不同材种不同材长的出材率,编制了苍梧县杉木出材率表。     

全站仪测树中材积模型选择

随着新型测树方法的出现,可直接获取的测树因子种类也越来越多.为研究不同树高处直径因子代替胸径因子建立材积模型的可能性,使用全站仪分别测量263株木棉树地径、胸径、树高1/3高处直径、树高1/2处直径,以回归分析的方式建立一元和二元材积模型.结果表明,对于同变量构建的模型,二次曲线、复合曲线、幂函数、指数函数模型的拟合结...     

红松人工林树干削度方程的研究

指出了削度方程不仅可用于推算单木及各材种的材积,更可用于林木生长过程的三维可视化重建,是林业生产实践中一种重要工具。以黑龙江省佳木斯市孟家岗林场60株红松人工林单木干形数据为例,以当前国内外林业中常用的简单削度方程、可变指数削度方程和分段削度方程为基础,采用SAS软件中的PROC NLIN模块对各模型参数进行求解,并采用确定系数(R2)、平均绝对误差(MAE)和均方根误差(RMSE)对各模型的拟合效果和预测能力进行了评价。结果表明:6种模型的整体拟合效果均相对较高,平均确定系数R2均在0.80以上;相同高度处的直径随着胸径的增加而呈增大趋势,但对树高的变化不够敏感;综合各项指标,该地区红松人工林的最优削度方程为可变指数削度模型(模型6),其模拟和预测R2均可达0.95以上,平均绝对误差均小于0.9cm,均方根误差也小于1.2cm。显然,筛选出的最优削度方程对精确红松人工林单木蓄积及指导合理造材具有重要作用。     

苍梧县杉木削度方程与材积比方程研究

在苍梧县并青林场等集体林场的伐区，随机量测样木５４８株，年龄为２０～２１年，直径分布６～２６ｃｍ，树高６～１６ｍ按２ｍ区分段，量测各段中央处的带皮直径，去皮直径，并现场造材，记录不同材种的出材率，并选择模型７为最适宜削度方程，方程１１为最适宜材积方程，确定了不同材种不同材长的出材率，编制了苍梧县杉木出材率表。     

湿地松材积出材率表的研究

根据５３２株湿地松伐倒木测径数据，通过１４组削度方程的比选，选定了符合湿地松树种的削度方程。此削度方程对任意直径限处的材长、任意高度处的直径及树干全材积等可获得高精度的估计。通过计算机理论造材，编制出湿地松一元和二元材种出材率表，各技术程序全部采用数学模型进行模拟，改变了过去用图解法传统编制材种数表的技术方法，提高了材种数表的精度     

Stem taper function for sweet chestnut (Castanea sativa Mill.) coppice stands in northwest Spain

? Context

Despite the economic importance of Castanea sativa Mill. in northwest Spain, studies of its growth and yield are practically non-existent.

? Aims

A compatible system formed by a taper function, a total volume equation, and a merchantable volume equation was developed for chestnut (C. sativa Mill.) coppice stands in northwest Spain.

? Methods

Data from 203 destructively sampled trees were used for the adjustment. Outliers were removed with a non-parametric local adjustment, providing a final data set of measurements taken from 3,188 sections which was used to test five taper models (compatible and non-compatible). A second-order continuous autoregressive error structure was used to model the error term and account for autocorrelation. Presence of multicollinearity was evaluated with the condition number. Comparison of the models was carried out using overall goodness-of-fit statistics and graphical analysis.

? Results

Results show that the models developed by Fang et al. in For Sci 46: 1–12, 2000 and Kozak in For Chron 80, N 4: 507–515, 2004 were superior to other equations in predicting diameter for chestnut coppice stands.

? Conclusion

The compatible volume system developed by Fang et al. in For Sci 46: 1–12, 2000 was finally selected as it provided the best compromise between describing stem profile and also estimating merchantable height, merchantable volume, and total volume and therefore provides the first specific tool for more effective management of chestnut coppice stands.     

A merchantable volume system for Pinus sylvestris L. in the major mountain ranges of Spain

? Accurate estimation of stem volume makes it possible to estimate the monetary value of one of the many commodities and services that forests provide to society, i.e. timber.

? In the present study a compatible volume system for Scots pine in the major mountain ranges of Spain (the Pyrenees, Southern Iberian Range, Northern Iberian Range, Soria and Burgos Mountains, Central Range and Galician Mountains) was developed with data from 2 682 destructively sampled trees. Several well-known taper functions were evaluated. A second-order continuous-time autoregressive error structure was used to correct the inherent autocorrelation in the hierarchical data, allowing the model to be applied to irregularly spaced and unbalanced data.

? The compatible segmented model of Fang et al. (2000) best described the experimental data. It is therefore recommended for estimating diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for the six mountain ranges analyzed.

? The non-linear extra sum of squares method indicated differences in mountain range-specific taper functions. A different taper function should therefore be used for each mountain range in Spain.

     

Merchantable volume system for pedunculate oak in northwestern Spain

A model is required for accurate estimation of the merchantable volume of pedunculate oak (Quercus robur L.) trees in Galicia, northwestern Spain. Accordingly, the purpose of the present study was to obtain equations for predicting merchantable volumes and stem profiles of individual trees. For this reason, two compatible and four non-compatible volume systems were initially evaluated and fitted to data from 251 destructively sampled trees which were collected in stands located throughout the area of distribution of the species in Galicia. The outliers were removed to provide a data set of measurements from 3 090 sections, which was then available for fitting. A second-order continuous autoregressive error structure was used to account for autocorrelation. Comparison of the models was carried out using overall goodness-of-fit statistics and box plots of residuals against relative height or diameter class. The compatible volume system of Fang et al. [22] provided the best compromise in describing the stem profile and estimating merchantable height, merchantable volume and total volume and is therefore recommended for pedunculate oak stands in Galicia.     

A merchantable volume system for major pine species in El Salto,Durango (Mexico)

A compatible volume system for the major pine species in El Salto, Durango (Mexico) was developed from data corresponding to 1930 destructively sampled trees. Several well-known taper functions were evaluated and compared against the model selected in a previous study of these pine species in the same area. Appropriate statistical procedures were used in model fitting to account for the problems of autocorrelation and multicollinearity that are associated with the construction of taper functions. A compatible segmented model best described the experimental data and was found to be better than the previously selected model. It is therefore recommended for estimating diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for the five species analyzed. The non-linear extra sum of squares method indicated differences in species-specific taper functions. A different taper function should therefore be used for each pine species.     

Total and Merchantable Volume Equations for Tectona grandis Linn. f. Plantations in Karnataka,India

Tectona grandis (teak) is one of the most important timber species worldwide and India is one of the major teak growing countries. Though some volume equations were developed in the past in India, merchantable volume equations (any top diameter or bole length) are not available. Moreover, the models developed were neither quantitatively and qualitatively evaluated nor validated with independent data sets. Hence, the objective of this study was to develop appropriate volume equations to predict total tree volume and merchantable volume for teak in Karnataka.

Linear and non-linear equations were used to model the relationship of the volume with respect to diameter at breast height (dbh) and total height. Merchantable volume equations for estimating merchantable volume to any minimum top diameter or bole length have also been constructed. The equations tested mostly fitted well to the data. Other models developed elsewhere tended to underestimate the volume, especially at dbh ≥ 23 cm. The geometric cylinder volume equation, in combination with a stem form factor of .40, is widely used for teak in Karnataka but they were found to be less precise compared to regression equations when applied to the present data set. Model validation indicated that models should be calibrated with local data for greater accuracy in the prediction.     

西江林业局尾巨桉人工林一元材种出材率表编制

在广东省西江林业局尾巨桉无性系人工林中选择并设置70个标准地,分别进行林分因子调查,同时选择163株样木以2.0 m或2.6 m段材长分径阶进行样木伐倒造材,以实际经济材造材出材率为基础拟合并选择较优的单株木一元材积比方程,然后根据材积比方程进行理论造材并编制尾巨桉单株木一元经济材出材率表;接着利用单株木一元经济材出材率表对所调查的标准地进行理论造材,以林分理论造材出材率为基础拟合并选择较优的林分一元材积比方程,最后根据材积比方程研制尾巨桉林分一元经济材出材率表。所编制的数表均符合国家精度检验标准,可为本地区桉树生产经营提供参考。     

Comparison of model forms for estimating stem taper and volume in the primary conifer species of the North American Acadian Region

? The performance of ten commonly used taper equations for predicting both stem form and volume in balsam fir [Abies balsamea (L.) Mill], red spruce[Picea rubens (Sarg.)], and white pine[Pinus strobus (L.)] in the Acadian Region of North America was investigated.

? Results show that the Kozak (2004) and Bi (2000) equations were superior to the other equations in predicting diameter inside bark for red spruce and white pine, while the Valentine and Gregoire (2001) equation performed slightly better for balsam fir.

? For stem volume, the Clark et al. (1991) equation provided the best predictions across all species when upper stem diameter measurements were available, while the Kozak (2004) and compatible taper equation of Fang et al. (2000) performed well when those measurements were unavailable.

? The incorporation of crown variables substantially improved stem volume predictions (mean absolute bias reduction of 7–15%; root mean square error reduction of 10–15%) for all three species, but had little impact on stem form predictions.

? The best taper equation reduced the predicted root mean square error by 16, 39, and 45% compared to estimates from the widely used Honer (1965) regional stem volume equations for balsam fir, red spruce, and white pine, respectively.

? When multiple taper equations exist for a certain species, the use of the geometric mean of all predictions is an attractive alternative to selecting the “best” equation.

     

Models for estimation of tree volume in the miombo woodlands of Tanzania

Volume of trees is an important parameter in forest management, but only volume models with limited geographical and tree size coverage have previously been developed for Tanzanian miombo woodlands. This study developed models for estimating total, merchantable stem and branches volume applicable for the entire miombo woodlands of Tanzania. We used data from 158 destructively sampled trees, including 55 tree species collected from wide geographical and biophysical ranges. We developed general and site-specific models with diameter at breast height only as the independent variable, together with models with both diameter at breast height and tree height. Leave-one-out cross-validation was used to evaluate the models. The total tree volume models that included diameter at breast height and tree height had appropriate predictive capabilities with relative root mean square errors (RMSE_r) ranging from 30.5% to 47.6%. The RMSE_r for total tree volume models with diameter at breast height only ranged from 39.9% to 48.0%. The site-specific models had slightly lower RMSEr values relative to the general models. The relative mean prediction error of the general total tree volume model with diameter at breast height and tree height was lower (0.6%) than those of the previously developed models (?30.7% to 31.2%). Based on the evaluations, we recommend the general total tree models to be applied over a wide range of geographical and biophysical conditions in Tanzania.     

Effect of utilization standard on wood supply and lumber yield

ABSTRACT

Although sustainable forest management is accepted worldwide in concept, challenges in the methods of implementation remain. Using local data sets from Alberta, Canada, we show that a simulation approach can assist the implementation of sustainable forest management by improved understanding of product potential and other forest ecosystem goods and services that forests can provide for a given forest inventory. This will assist facilitating trade-offs among them for an optimal wood utilization strategy to achieve sustainable forest management. In this example, effects of wood utilization standard on merchantable volume, lumber volume, and number of trees that can produce at least one piece of lumber are quantified, and a conversion method for wood volumes under different wood utilization standards is presented. Wood utilization standard is the combination of stump height and diameter inside bark at merchantable height, which considerably influences available volume quantity of forest resource. However, such influences have not been quantified for sustainable forest management implementation. Our results not only confirmed that merchantable and lumber volumes increased with decreasing stump height and diameter inside bark at merchantable height, but also revealed that this trend will not hold when diameter inside bark at merchantable height is less than 7 cm.