毛白杨生长的灰色动态模型

本文根据毛白杨树干解析木资料,应用灰色系统理论中的GM(1,1)模型和Vcrhulst模型,对毛白杨生长进行了预测分析。结果表明,GM(1,1)模型优于Verhulst模型;根据树木生长变化规律,分段建模,效果很好;提出了毛白杨树高、胸径及材积的总生长量、平均生长量、连年生长量的动态模型。     

毛白杨主要林分因子生长及相关关系研究

该文在河北省范围内调查片状和带状毛白杨林分标准地 14 9块 ,研究林分平均胸径、平均高、胸高断面积、蓄积等主要林分因子的生长情况 ,并建立了主要因子的生长模型和相关关系模型 ,可用于毛白杨林分生长预测和评估     

2个毛白杨无性系生长差异性分析

在对甘肃天水的毛白杨优良无性系试验点进行阶段性研究,通过样地调查,树木胸径、树高、材积的测定和计算及其解析木的测定与分析,建立了2个毛白杨无性系的生长过程总表和生长模型。然后,用t检验法,对2个毛白杨无性系的生长差异性进行分析,结果表明：河北1609号毛白杨优良无性系不论在胸径、树高、材积方面的总生长量都大于易县雌株毛白杨,而且,树干更显通直。因此认为,1609号毛白杨无性系在该地有更好的表现和培养前途,这对天水地区毛白杨资源的开发利用与保护有重要意义。     

天然阔叶林生长收获动态预估模型的研究

根据天然阔叶林固定样地材料,选择合适的生长方程构建生长收获动态预估模型,并用遗传算法求解参数.模型经检验适用,实际应用误差较小,精度较高.应用天然阔叶林生长收获动态预估模型,只要输入现实林分年龄、立地质量类型、每公顷断面积,即可输出现实林分和未来林分蓄积量,应用简便,满足生长和收获的一致性,在林业生产上有推广应用价值.     

林分生长和收获预估模型综述和分析

一、概述森林资源动态预测涉及到森林的生长和收获预估,常用的方法有二:一是以抽样调查为主的直接调查法;一是根据林分生长和收获预估模型的间接预估法。林分生长和收获预估模型,是根据各种立地、不同发育阶段的森林实况,经一定数学方     

林木直径分布收获模型综述

一、林分生长与收获模型概述林分生长与收获模型是客观地预测林分的生长、收获的重要手段,是森林经营工作者经营森林的指南。由于现实林分结构变化很大,经营目的以及生长和收获模型使用者的需要不同;特别是由于计算机在林业生产中的广泛应用,采用的林分生长与收获模型数目较多、形式多样。为了便于比较分析,许多学者曾根据模型的构造原理、建模方法和模型的特点,进行过不同的分类。如Murro(1974),Hamilton(1974),EK(1981),Atpoiiiehho(1981),     

湘南引种三倍体毛白杨生长模型研究

对三倍体毛白杨在湘南地区的早期生长过程进行了分析,并对胸径、树高、材积等生长模型进行了研究。     

山西省毛白杨杂交品种区域化试验的研究

在毛白杨的4个气候区设点观测试验,通过不同区试点无性系间的差异分析和基因型与环境交互作用的多重比较,以及抗逆性调查和生态因子与生长性状的多元回归分析,综合评定出各气候区今后发展的毛白杨杂交良种及其生长潜力模型。区域化试验结果表明毛白杨杂交品种96和73可以在晋南、晋东南、晋中一带大力推广;窄冠毛白杨中27、南毛新(T31)、L4可用于营造农田防护林网;92虽然生长快但抗风折和抗干水泡溃疡病能力差,应予控制。     

Fuzzy关系方程在毛白杨苗木生长性状相关分析中的应用

本文根据山东省省选12株毛白杨(Populus tomentosa Carr.)古树的38株无性系苗木资料,利用Fuzzy关系方程对苗高生长与7个形态性状进行模糊综合评判。结果表明,叶片长与苗高生长关系最密切。提出了应用形态性状估测苗高生长的GM(0,N)模型。     

毛白杨雌株生长优势与利用

毛白杨为雌、雄异株。根据我们几年来的观察,发现雌株比雄株具有较强的生长优势,因此充分利用雌株的生长优势,是较快地提高林木蓄积量的有效措施之一。一、毛白杨雌株生长优势1973年以来,我们通过对雌雄紧邻,8—10年生的300株毛白杨进行实测,结果见表1。     

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 reduced growth model based on stand basal area. A case for hybrid poplar plantations in northeast Spain

Whole-stand models normally require data on initial stand basal area and dominant height. Dominant height measurements are time-consuming and often imprecise, compromising subsequent predictions. Poplar plantations provide a special case where basal area correlates with site index; a whole-stand model could thus be based on stand basal area. We report a static model constructed by the generalized algebraic difference approach (GADA) for poplar plantations for three different hybrid poplars (Populus × euramericana (Dode) Guinier “I-214”, “MC”, and “Luisa Avanzo”) in northeast Spain. The transition function was based on current stand basal area and was fitted with data from 158 permanent plots ranging from 1- to 17-year-old plantations. Merchantable stand volume was estimated by a volume equation where height was predicted by a height–basal area relationship based on 458 temporary plots. The model differences between clones were compared using the nonlinear extra sum of squares method. Significant differences were detected, while Luisa Avanzo presented the highest merchantable volume at the end of the rotation. Errors in basal area predictions were below 20% within 6 years in the case of Luisa Avanzo and MC clones, and within 3 years in the case of I-214. Our research showed that satisfactory predictions can be obtained using GADA with a single transition function based on an easily measurable variable such as stand basal area.     

基于混合效应模型的杉木人工林蓄积联立方程系统

建立江西杉木人工林基于非线性混合效应方法的林分优势木平均高和断面积模型以及基于对数形式线性混合效应蓄积模型的联立方程组,利用验证数据与传统模型回归方法的模拟结果进行比较分析。结果表明,优势木平均高是联立方程组最基本的组成部分。通过考虑优势木平均高和林分断面积模型中参数的随机效应以及3个因变量间的相关性,则蓄积模型中参数的随机效应可以忽略。优势木平均高决定着林分断面积预测的准确性,而优势木平均高和林分断面积又是预测蓄积的主要误差来源。基于混合效应模型方法的模拟结果明显好于传统回归估计方法。进行预测时,通过解释联立方程组中因变量相互间的相关性,利用已被观测的变量能够提高未观测变量的估计精度。     

A taper function for Pseudotsuga menziesii plantations in Spain

Five stem taper models belonging to three different taper function categories were fitted to data corresponding to 282 Pseudotsuga menziesii trees. The trees were selected in the area surrounding 61 research plots installed in Galicia, Asturias and the Basque Country, northern Spain. The models were simultaneously fitted to observed values of diameter outside bark and inside bark. A third-order continuous-time autoregressive error structure was used to account for autocorrelation. Selection of the best model was based on both numerical (goodness-of-fit statistics) and graphical analysis (plots of residuals against position along the stem and against tree size). The three-segmented taper model finally selected has the advantage of being compatible with both a merchantable and a total stem volume equation.     

Late-entry commercial thinning effects on Pinus banksiana:growth,yield, and stand dynamics in Québec,Canada

We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine(Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area(BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm(25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume(GMV) tree-1by 46% compared to the control. The 27% BA removal had twice as much GMV ha-1compared to the 47% BA removal after15 years. Moreover, cumulative GMV ha-1was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15-year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce(Picea mariana(Mill.) B.S.P.), white birch(Betula papyrifera Marsh.), and trembling aspen(Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.     

杨树修枝理论和技术研究进展

杨树修枝是杨树速生丰产后期经营管理中一项重要的措施,本文综述了修枝对杨树生长、材质以及林下经济的影响。修枝对杨树树高、材积生长量的影响因树种、立地、修枝强度的不同规律不同;修枝会降低胸径的生长量,提高萌枝数量,但可以提高材质。修枝对材质的影响表现在尖削度减小、节子减少、形数和形率增加等。修枝可以增强林下作物光合作用,促进林下植物生长,提高产量;实践中,修枝强度、起始年龄、修枝季节应因树种而异。目前,对于杨树修枝的研究多为短期的、单方面的,系统综合研究尚需进一步加强。     

人工林毛白杨木材解剖构造与染色效果相关性的研究

为探讨木材构造和木材染色效果之间的相关性变化规律，本研究测字５株３４块人工林毛白杨 的解剖构造及其木材染色效果，对二者的相关性进行了多元回归分析。结果表明，毛白杨木材染色效果与解剖因子之间有一定的相关关系，各染色效果指标与木材解剖因子间的复相关系数在０．４８３６－０．７９９８之间，采用比较多元回归分析标准回归系数的方法，确定了影响毛白杨木材染色效果的主要解剖因子为导管比量、木纤维比量和木射线量等因子。     

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.     

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.     

Predicting and calibrating diameter distributions of Eucalyptus grandis (Hill) Maiden plantations in Zimbabwe

Diameter distribution models for even-aged Eucalyptus grandis plantations in Zimbabwe were developed using the two-parameter Weibull function. The analysis was based on data from Correlated Curve Trend (CCT) experiments replicated on four different sites. Parameters of the Weibull distribution were predicted using stand characteristics as regressors. Two sets of parameter models were estimated: a set with and one without stand basal area as a predictor. Stand variables such as dominant height, age, site index and number of stems were used in both sets. The models were further calibrated to result in a given number of stems and stand basal area simultaneously. The usability of constructed models was tested both in prediction of yield in a stand inventory situation and in simulation of growth in connection with different growth models. The results indicated that models not including stand basal area produce considerably less precise stand volume estimates compared to models including also stand basal area. Calibration improved the accuracy of diameter distribution models. In growth simulation diameter distribution models can be connected both to single tree growth models and to stand projection models. The usability of calibration in growth simulation depends on the accuracy of the prediction of stand characteristics.