Development and validation of stem volume models for Pinus kesiya in Benguet province,Philippines

Stem volume equations (overbark) were developed, using established volume equation forms, and validated using a subset of the data collected for Pinus kesiya in Benguet province, Philippines. A total of 481 trees from Pinus kesiya stands in Benguet were measured through non-destructive sampling. The data set was randomly split into two subsets for initial model development (80% of the data set) and validation (20% of the data set). The performance of the different models was evaluated using evaluation statistics: fit index (FI), root mean square error (RMSE), bias (ē), absolute mean difference (AMD) and coefficient of variation (CV%). The best model forms were selected for final model development using the combined data set (100%). Overall, volume models with two independent variables (DBH and total height) performed better than models with only one (DBH). In the validation of the models, it was observed that AMD of the models converged in the DBH classes with higher sample size. Furthermore, one of the best models in this study, Model 2, also performed better when compared to the general single volume equation developed for the non-dipterocarp species in regions 1, 2, 3 and the Cordillera Administrative Region (CAR) of the Philippines. The models developed in this study may assist forest managers acquire improved stem volume predictions of Pinus kesiya in the forests of Benguet, Philippines.     

兴安落叶松树干去皮直径预测模型

利用兴安落叶松解析木数据,比较了树干去皮直径预测的3种类型模型:Grosenbaugh的比率方程式、回归模型和削度方程。Grosenbaugh的比率方程式有很大的灵活性,没有参数不需要模型拟合。总体评价和模型分段比较表明,回归模型有较小的预测误差,尤其是Cao and Pepper提出的含有带皮直径、树高、相对树高、胸径处的带皮直径和去皮直径变量的模型。由于削度模型不含有带皮直径变量,因此产生较大的去皮直径预测误差。不同类型的模型在森林经营过程中都有一定的适应性。     

Estimating and predicting bark thickness for seven conifer species in the Acadian Region of North America using a mixed-effects modeling approach: comparison of model forms and subsampling strategies

In many situations, information on stem diameters inside bark (dib) are more desirable than on diameters outside bark (dob). However, obtaining dib measurements is usually expensive, time-consuming, and prone to significant measurement errors when done on standing trees. Many bark thickness equations have been proposed to estimate the dibs of standing trees. In this study, we compared several commonly used bark thickness equations for seven conifer species in the Acadian Region of North America. Mixed-effects modeling techniques were employed to fit linear and non-linear bark thickness equations. We found the equation proposed by Cao and Pepper (South J Appl Forestry 10:220?C224, 1986; Eq. 5) performed significantly better than other equations for most of our study species. The Cao and Pepper (South J Appl Forestry 10:220?C224, 1986) equation is a function of dob, relative height in the stem, tree height, and the ratio of dib to dob at breast height. The mean absolute bias was found to be reduced up to 74% compared with using a fixed ratio approach employed in the widely used Northeastern variant of the Forest Vegetation Simulator (FVS-NE) growth and yield model. Leave-one-out cross validation was further performed to determine the location of suitable prior measurements in the prediction process for three of the most well-behaved equations. Results show that no unified prior measurement can provide best predictive abilities across all species as the choice of prior dib measurements depends on both species and bark thickness equations.     

A set of models for individual tree merchantable volume prediction for <Emphasis Type="Italic">Pinus pinaster</Emphasis> Aiton in central inland of Portugal

The study purpose selected among several candidate models for best individual tree, over bark, total volume model, volume ratio model to any top height limit and taper model for maritime pine (Pinus pinaster Aiton) in the regions of Pinhal Interior Sul and Beira Interior Sul, Portugal. The data used in the study were collected from 144 felled trees, corresponding to 995 diameter/height measurements. To select among the best models, several statistics were computed during model fitting, and the independent validation procedure was used to evaluate model fitting, collinearity and prediction performance. A ranking index was used to support the final decision. The analysis of models studentized residuals distribution showed that some regression model assumptions, such as normality and homogeneity, were not met. To overcome this unideal situation, the models selected were then fitted again using robust regression and weighted regression techniques. The set of adjusted models will allow the prediction of individual tree, over bark, total volume and merchantable volume to any merchantable limit, for both species and region to support management decisions.     

Modeling stem profile of Lebanon cedar,Brutian pine,and Cilicica fir in Southern Turkey using nonlinear mixed-effects models

The Max and Burkhart segmented taper model was fitted using nonlinear mixed-effects modeling techniques to account for within- and between-individual stem profile variation for Lebanon cedar (Cedrus libani A. Rich.), brutian pine (Pinus brutia Ten.), and cilicica fir (Abies cilicica Carr.) in Turkey. About 75% of the trees were randomly selected for model development, with the remainder used for model validation. Diameter measurements from various heights were evaluated for tree-specific calibrations by predicting random-effects parameters using an approximate Bayesian estimator. The procedure was tested with a validation dataset. Predictive accuracy of the model was improved by including random-effects parameters for a new tree based on upper stem diameter measurements. Prediction in stem diameter was less biased and more precise across the all sections of bole when compared to predictions based only on fixed-effects parameters. In the future, the proposed mixed models can be applied to region wide three species stands by fitting the model to a larger data set that more closely represents regional variation.     

落叶松种间及其杂种生长与形质性状评价研究

[目的]通过对落叶松种间及其杂种生长与形质性状评价来定向选育优良落叶松建筑材。[方法]以辽宁省大孤家林场32年生的落叶松试验林为实验材料,对落叶松属日本、兴安、长白及华北4个落叶松种,及以日本落叶松为母本的日本×兴安、日本×华北、日本×长白、日本×日本杂种的生长和形质性状进行变异规律分析,并采用模糊数学隶属函数对其差异显著指标进行综合评价。[结果]表明:落叶松种和杂种间生长差异显著(p<0.01),杂种胸径、树高和材积总生长量与母本差异不显著,却显著高于相应父本;杂种之间的生长差异体现在林分的前10年,随着林龄的增大优势逐渐减退;树冠特征因子中的枝下高、冠长、枝条直径、长度、角度和干形特征因子中的高径比、树干圆满度、节子直径、长度、角度在落叶松种和杂种间差异显著。基于上述指标进行了生长和形质性状综合评价,排名前三位的分别为日本×兴安、日本×长白和日本落叶松。32年生时日本×兴安的胸径、树高和材积分别为18.69 cm、21.62 m和0.339 2 m³;日本×长白的为18.44 cm、23.85 m和0.339 6 m³;日本落叶松的为19.36 cm、21.31 m和0.335 7 m³;而且它们在适应性上也具有明显优势。[结论]日本×兴安、日本×长白和日本落叶松适合作为定向培育建筑材的优良品种在东北地区重点推广。     

Segmented taper equations with crown ratio and stand density for Dahurian Larch (<Emphasis Type="Italic">Larix gmelinii</Emphasis>) in Northeastern China

Segmented taper equation was selected to model stem profile of Dahurian larch (Larix gmelinii Rupr.). The data were based on stem analysis of 74 trees from Dailing Forest Bureau in Heilongjiang Province, Northeastern China. Two taper equations with crown ratio and stand basal area were derived from the Max and Burkhart’s (1976) taper equation. Three taper equations were evaluated: (1) the original equation, (2) the original equation with crown ratio, and (3) the original equation with basal area. SAS NLIN a...     

Development of height curves for Japanese larch in relation to GIS-derived site index

The objectives of this study were: (1) to relate the height growth pattern to the GIS-derived site index, (2) to construct various types of polymorphic height curves, and (3) to select the most accurate height curve for Japanese larch (Larix kaempferi). A total of 14 dominant trees were felled for stem analysis. Richards' function was first fitted to the height/age dataset recorded from stem analyses of 14 trees, and its parameters (i.e., A, k, and m) were then estimated for each sample tree. The relationship between parameter A and the GIS-derived site index was significant, while that of parameters k and m were not significant. The 12 height curve equation forms developed from the Richards' function were then fitted to the dataset consisting of 563 observations of height, age, and GIS-derived site index derived from 14 trees. All height curves were unbiased and provided an equally good fit. The shape of the height curves differed among sites of different site indices. These results indicated that Richards' function was sufficiently flexible to represent the polymorphic height growth pattern of Japanese larch. Finally, the best-fit height curve was selected so that accurate height growth predictions would be possible at any given age and site.     

基于分位数回归的华北落叶松干形曲线模拟

干形是反映树干外部形态的重要指标,也是评价干材价值的重要依据,而削度方程是描述树木干形好坏的一个重要定量指标,其对干形模拟的准确性直接决定着树干材积和森林蓄积的估算结果。以河北省塞罕坝机械林场华北落叶松人工林为研究对象,基于4个常见的简单削度方程,模拟了260株样木的干形曲线,采用调整后决定系数(Ra^2)、均方根误差(RMSE)、平均误差(ME)和平均误差绝对值(MAE)评价模型的拟合效果和检验效果,筛选最优的基础模型,并利用分位数回归技术,构建人工华北落叶松干形曲线模型。结果表明,4个简单削度方程中,Kozak方程对华北落叶松干形的拟合效果最好(Ra^2=0.934,RMSE=1.985cm),检验结果也是最优的(ME=0.125cm,MAE=1.212cm)。因此,基于Kozak方程,结合分位数回归技术建立了华北落叶松干形曲线,相较于基础模型,分位数回归模型的拟合优度进一步提高。当分位点设置为0.1时,模型对靠近下部和上部的树干干形拟合效果较好;当分位点设置为0.5时,模型对位于中部的树干干形拟合效果较好;当分位点设置为0.9时,模型对树干基部的拟合效果较好。可见,分位数回归技术使模型具有更强的灵活性。     

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）。     

滇西南巨尾桉人工林木根径、胸径与树高模型研究

为研究巨尾桉人工林林木根径、胸径与树高数学模型,在滇西南的双江县选取138株（其中建模样本103株,检验样本35株）树干健全、通直圆满、无分杈的巨尾桉人工林样木,采集其根径与树高、胸径与树高成对数据。利用SPSS 21.0回归分析,分别建立线性方程、对数曲线、指数曲线和Logistic曲线等11个数学模型,以决定系数（R²）、估计值的标准误（SEE）、均方差（RMSE）、平均绝对偏差(MAD)、相对误差（RS）、模型预估精度（P）、显著性(Sig)P值作为模型评价指标,对比11个模型的拟合效果。结果表明,11个根径—树高模型显著性（Sig）P<0.001,其中有9个模型的预估精度大于97%,回归方程达到极显著水平,拟合效果较好;11个胸径—树高模型显著性（Sig）P<0.001,其中9个模型的预估精度大于97%,回归方程达到极显著水平,拟合效果也较好。通过对各项评价指标进行比较分析,确定三次项曲线H=a₀+a₁DR+a₂DR²+a₃DR³是拟合效果最好的根径—树高数学模型,代入拟合参数后的根径—树高数学模型表达式为H=11.069901-0.729389DR+0.096782DR²-0.001984DR³;线性方程H=a₀+a₁D是拟合效果最好的胸径—树高数学模型,代入拟合参数的胸径—树高数学模型表达式为H=4.818702+0.891217D。     

Development and validation of a stem volume equation for Cupressus lusitanica in Gergeda Forest,Ethiopia

Stem volume equations were fitted for Cupressus lusitanica in Gergeda Forest, Ethiopia using six different established equation forms. A total of 260 trees were measured for their diameter at breast height (D), total height (H?)and stem volume using destructive sampling methods. The data set was randomly divided into equal size for equation development and equation validation. Five fit statistics comprising of the fit index, root mean square error, bias (ē?), absolute mean deviation and coefficient of variation were used to evaluate the performance of each equation. Among the different equations, the Schumacher and Hall function of the form V = b₁D^b2H^b3 (model 5), which estimates volume (V?) using diameter at breast height and total height as predicting variables, performed best and was then fitted to the combined data set for prediction of volume over-bark of C. lusitanica in Gergeda Forest. Overall, volume equations with two independent variables (D and H?) performed better than those with only one variable (D). The equations developed in this study can provide forest managers with accurate estimations of stem volumes for C. lusitanica in Gergeda Forest.     

Aboveground biomass equations for individual trees of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>, <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> and <Emphasis Type="Italic">Larix kaempferi</Emphasis> in Japan

Generic equations are proposed for stem, branch and foliage biomass of individual trees in even-aged pure stands of Cryptomeria japonica, Chamaecyparis obtusa and Larix kaempferi. Biomass data was collected from a total of 1,016 individual trees from 247 stands throughout Japan, and five regression models were assessed by root mean square error, mean bias, fit index (FI), and AIC. The results show that a power equation using diameter at breast height (dbh) and height is the most suitable for all species and components. This equation is more accurate than the familiar power equation that uses ‘dbh² height’, and it expresses the greater volume of branch and foliage mass of trees with a lower height/diameter ratio. A power equation using dbh is more reasonable for models with dbh as the only independent variable and more accurate than a power equation using ‘dbh² height’ for estimating branch and foliage mass. Estimating error for branch and foliage mass is larger than that for stem mass, but the entire aboveground biomass can be estimated with an error of less than 19%, except in the case of small trees with dbh less than 10 cm.     

广西马尾松经济材出材率表编制研究

以马尾松人工林作为研究对象,用伐倒木样木数据,经干形分析和多指标精度比较,选定最佳的削度方程;通过树皮率方程和树高曲线方程进行计算机理论造材,依据各经济材种规格,编制出马尾松胸径树高二元经济材出材率表。经检验,以该方法编制的出材率表达到林业数表模型编制的精度要求。     

Modelling diapause termination and phenology of the Japanese beetle,Popillia japonica

We deve?loped a mechanistic, stage-structured model simulating the phenology of Popillia japonica. The model simulates the influence of soil temperature on the larval diapause termination and on the development rate function of post-overwintering larvae and pupae. Model parameters are estimated based on literature evidence for pupae development and on a parameterisation process that allows estimating parameters for larval diapause termination and for the development rate function (and the related uncertainty) of post-overwintering larvae. Data used for model parameterisation and validation refer to time-series adult trap catches collected during the P. japonica monitoring programme performed by the Phytosanitary Service of Lombardy Region within the infested area in Lombardy (Italy) from 2015 to 2019. A total of 12 randomly selected locations are used to estimate biologically realistic model parameters (parameterisation dataset). We applied a Jackknife nonparametric resampling procedure on the parameterisation dataset to quantify uncertainty associated with parameters’ estimates. Parameterised model is then validated on time-series adult trap catches data referring to a different set of 12 randomly selected locations (validation dataset) surveyed in Lombardy. The model successfully predicted the beginning of adult emergence and the overall curve of adult emergence in the validation dataset. The model presented can support the definition of the best timing for the implementation of monitoring and control activities for the local and the area-wide management of P. japonica.

     

Stem taper equations for poplars growing on farmland in Sweden

We developed a simple polynomial taper equation for poplars growing on former farmland in Sweden and also evaluated the performance of some well-known taper equations. In Sweden there is an increasing interest in the use of poplar. Effective management of poplar plantations for high yield production would be facilitated by taper equations providing better predictions of stem volume than currently available equations. In the study a polynomial stem taper equation with five parameters was established for individual poplar trees growing on former farmland. The outputs of the polynomial taper equation were compared with five published equations. Data for fitting the equations were collected from 69 poplar trees growing at 37 stands in central and southern Sweden (lat. 55-60° N). The mean age of the stands was 21 years (range 14-43), the mean density 984 stems ha -1 (198 3,493), and the mean diameter at breast height (outside bark) 25 cm (range 12-40). To verify the tested equations, performance of accuracy and precision diameter predictions at seven points along the stem was closely analyzed. Statistics used for evaluation of the equations indicated that the variable exponent taper equation presented by Kozak (1988) performed best and can be recommended. The stem taper equation by Kozak (1988) recommended in the study is likely to be beneficial for optimising the efficiency and profitability of poplar plantation management. The constructed polynomial equation and the segmented equation presented by Max & Burkhart (1976) were second and third ranked. Due to the statistical complexity of Kozak’s equation, the constructed polynomial equation is alternatively recommended when a simple model is requested and larger bias is accepted.     

Stem form variations in the natural stands of major commercial softwoods in eastern Canada

Stem form is often used as a sawlog assortment criterion and has an important effect on lumber recovery and mechanical properties. Based on 7018 stems collected from the natural stands in 3 regions in eastern Canada, this study quantified the variations in stem form (taper, sweep and eccentricity) for five major commercial softwood species, viz., jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana), white spruce (Picea glauca), red spruce (Picea rubens) and balsam fir (Abies balsamea). The majority of the stems had a diameter at breast height (DBH) ranging from 10 to 32 cm and total tree height from 10 to 20 m. Stem taper and butt taper increased steadily from 0.38 to 1.75 cm/m and from 0.74 to 4.23 cm/m, respectively, with DBH increasing from 8 to 48 cm. Stem sweep and basal sweep ranged from 0.12 to 7.28 cm/m and from 0.12 to 9.85 cm/m, respectively, with mean values of 0.87 and 0.95 cm/m. There were no significant differences in stem sweep and basal sweep between DBH classes and both sweeps distributed over a wide range within DBH classes, species and regions. About 0.77% of the stems and 1.2% of the butt logs had seriously curved shapes (sweep >3.0 cm/m). Eccentricity (ratio of smaller diameter to larger diameter) at the breast height (0.96) was very close to 1. Balsam fir and jack pine had the best and worst stem forms, respectively, while stem forms in black spruce were in-between. Butt logs were most seriously curved in red spruce and most tapered in white spruce. Region C (mainly eastern Quebec and the Atlantic Provinces) produced stems with smaller butt taper, basal sweep and stem sweep and larger eccentricity compared with other regions in eastern Canada. Overall stems in eastern Canada have a good stem form in terms of taper, sweep and eccentricity. The evaluation of stem form provides valuable timber quality information for the wood industry to optimize wood processing as well as for forest managers to define appropriate silvicultural regimes to improve stem form and economic value.     

Developing a taper model for the Pinus elliottii × P. caribaea var. hondurensis hybrid in South Africa

A relatively new hybrid, Pinus elliottii × P. caribaea var. hondurensis (Pexc), for which a taper model does not exist, is being planted commercially in South Africa. This study primarily focused on developing a taper model for Pexc in South Africa. Taper data were collected from a total of 363 trees, in the Mpumalanga and Limpopo provinces, using a random sampling method. A subsample was selected to determine if altitude, rainfall, temperature or soil have a significant influence on the taper of Pexc. Only rainfall significantly influenced the overall taper. The Max and Burkhart segmented polynomial taper model, as well as the Kozak88, Kozak01 and Kozak02 variable exponent taper models, were fitted, compared and tested using the statistical analysis system (SAS). The predictive ability of the models was evaluated based on the results from the mean bias, standard deviation, the standard error of prediction and the average percentage deviation. The Kozak02 model had the best fit overall followed by the Max and Burkhart model (MB76). The MB76 model, however, predicted the volumes more accurately than the Kozak02 model.     

大老岭自然保护区日本落叶松林凋落物分解及养分释放研究

[目的]研究外来引进树种日本落叶松林凋落物对土壤养分的影响。[方法]采用分解袋法分别对18年生和24年生日本落叶松林以及周围针阔混交林凋落物的分解和养分释放规律进行了研究。[结果]凋落物分解和养分释放速率均表现为针阔混交林日本落叶松纯林;24年生日本落叶松林18年生日本落叶松林。其中不同林分的凋落物残留率与时间呈指数相关,凋落物年分解系数(K)也表现为针阔混交林(0.555 6)24年生日本落叶松林(0.445 0)18年生日本落叶松林(0.366 2)。凋落物分解速率与初始N元素含量呈极显著正相关,而与C/N比呈显著负相关,高的木质素含量对凋落物的分解有一定影响。C元素、K元素表现为直接释放模式,而研究中C/N比和C/P比相对较高,使N元素和P元素均表现为先富集后释放的模式。各养分元素的残留率总体呈现出18年生日本落叶松林24年生日本落叶松林针阔混交林的格局。[结论]不同林分凋落物分解和养分释放速率差异较大。凋落物年分解系数表现为针阔混交林24年生日本落叶松林18年生日本落叶松林。     

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.