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应用有约束条件的非线性最小二乘法建立以地位指数和年龄为解释变量的林分最大断面积模型,按照变量间的一致性原则,编制了杉木人工林标准收获表,为生产应用提供了科学依据。 相似文献
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《林业工程学报》2017,(6)
为实现油桐籽含油率的快速检测,采用近红外光谱结合化学计量学方法对油桐籽含油率的测定进行了研究。107个样本用Kennard-Stone法划分为校正集(80个)和验证集(27个)。光谱经预处理方法优化,确定一阶导数结合均值中心化预处理最优。分别采用竞争性自适应重加权算法筛选变量及小波变换压缩变量,比较了偏最小二乘法与径向基神经网络法所建模型的预测性能,确定竞争性自适应重加权算法筛选出的8个变量用于偏最小二乘法建模,所建模型预测性能最好:验证集相关系数0.927,均方根误差2.08,相对标准偏差为3.99%。结果表明竞争性自适应重加权算法筛选变量结合偏最小二乘法建模,所建模型简单,精度较好,可用于油桐籽含油率的快速检测。 相似文献
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为了在生物量建模过程中得到回归模型的最优估计,针对回归模型存在的异方差性,提出用怀特检验方法来定量分析模型,再结合残差分布图来辅助判断,并应用怀特检验方法和残差分布图实例分析了普通最小二乘法拟合栎类生物量模型结果存在异方差性,建议采用加权最小二乘法拟合栎类生物量模型。 相似文献
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椴树胸径 根径和立木材积相关关系的研究 总被引：5，自引：0，他引：5
通过利用椴树（ＴａｌｉａＳＰ．）的胸径和立木材积、根径和立木材积间的相关性，运用回归分析的方法建立了回归方程，经过选择，确定了各自的合理模型，为了克服材积方程异方差性的影响，采用加权最小二乘法估计了模型的参数，找到了胸径和立木材积、根径和立木材积的最佳模型，提高了材积方程的适用精度。 相似文献
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通过对３７０株油松根径（Ｄ＿ｏ）和立木材积的相关分析，建立了回归方程，并运用加权最小二乘法估计了回归方程的参数，确定了最合理模型： 相似文献
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森林蓄积量受遥感因子与地形因子的影响,但这些因子间存在多重相关性,会影响模型稳定性与精度。针对森林蓄积量遥感估测自变量间存在多重共线性问题,采用异于传统最小二乘的偏最小二乘方法建立密云县森林蓄积量遥感估测模型。先对可能影响蓄积量的因子进行分析,选取既存在相关性又对模型显著性有影响的因子为森林蓄积量估测的自变量。用预留的样本对模型进行检验,预测值与实测值相比精度达到90.1%。将通过检验的模型对整个密云县进行反演,得到密云县估测森林蓄积量为2 447 695.203 m3。 相似文献
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【目的】基于机载激光雷达数据建立结构稳定的林分地上生物量预测模型,考虑最小二乘、混合效应和贝叶斯等参数估计方法对最优生物量预测模型选择进行探讨,为生物量建模方法研究、生物量估测提供科学依据,为冬奥核心区实现“双碳”目标和生物量模型计算提供技术支撑。【方法】基于崇礼冬奥核心区2种森林类型(华北落叶松和白桦)62块实测样地及对应的激光雷达数据,通过变量筛选分别建立最小二乘、混合效应和贝叶斯生物量模型,应用确定系数(R2)、均方根误差(RMSE)、残差、总体相对误差(TRE)评价模型,采用留一交叉法验证模型精度。【结果】筛选出相关性较高的激光雷达变量共20个,最终进入模型的自变量3个。拟合效果最好的是Logistic混合效应模型(RMSE=22.99 t·hm-2,R2=0.768,TRE=6.08%),分树种建立模型后华北落叶松模型拟合效果提升(RMSE=22.92 t·hm-2,R2=0.795,TRE=7.45%),白桦模型预测精度提高(RMSE=23.34 t·hm... 相似文献
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林分生长与产量模型系统研究综述 总被引：12，自引：1，他引：12
本文阐述了影响林分生长和产量的 5个因子 ,即立地指数、林分年龄、林分密度、生境类型和林分结构。介绍了林分水平、径级水平和单株木水平的林分生长和产量预测模型系统的一些代表性模型系统。还介绍了一些典型的生长和死亡模型。林木和林分是两级不同水平的生态系统。作者提出了建立以生态系统特性 (如系统的整体性、同时性、组成成分间交叉相关性等 )为基础的系统化模型。通过建立联立方程系统 ,用 3阶段最小二乘法拟合回归参数 ,可望提高林分生长和产量预测模型的真实性和估测精度 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):97-102
An individual tree basal area increment model was developed for Norway spruce [Picea abies (L.) Karst] in mixed stands of spruce and birch in Estonia. Different regression equations were fitted for different combinations of variables to obtain biologically tractable interactions between growth and factors affecting it. The best fit index of the regression model was pursued in trials with variable combinations. The basal area increment was chosen to describe the tree growth and both the diameter and age of the tree were included as independent variables. The logical growth relationships were obtained. The basal area increment has a culmination introduced by the simultaneous influence of tree size and age explicitly included in the model. The stand level attributes contributed modestly to the explanatory power of the model because of the narrow range of stand conditions sampled. The present model is applicable to Estonian conditions. 相似文献
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IntroductionDahurianlarch(L8risgmeliniiRupr.)isoneofthemostimportanttimberspeciesinChina.AsaresuItofovercuttingforseveraIdecades,thenaturaIDahurianIarchforestresourcesaredecliningrapidly.PIantationsofdahurianIarchhavebecomeanimportantpartofforestpreserveresourcesinDaxing'anMountains.ConsequentIystudyingthegroWthofDahurianlarchandformingtheforesttabfesareofsignrficancetofor-estproduction.ThispaperpresentsinformationongroWthandyieIdmodeIsofDahurianlarchpIantations.MethodsDataof4O5stema… 相似文献
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In view of the difficulties in stand volume estimation in natural forests, we derived real form factors and models for volume estimation in these types of forest ecosystems, using Katarniaghat Wildlife Sanctuary as a case study. Tree growth data were obtained for all trees (dbh >10 cm) in 4 plots (25 × 25 m) randomly located in each of three strata selected in the forest. The form factor calculated for the stand was 0.42 and a range of 0.42 0.57 was estimated for selected species (density >10). The parameters of model variables were consistent with general growth trends of trees and each was statistically significant. There was no significant difference (p>0.05) between the observed and predicted volumes for all models and there was very high correlation between observed and predicted volumes. The output of the performance statistics and the logical signs of the regression coefficients of the models demonstrated that they are useful for volume estimation with minimal error. Plotting the biases with respect to considerable regressor variables showed no meaningful and evident trend of bias values along with the independent variables. This showed that the models did not violate regression assumptions and there were no heteroscedacity or multiculnarity problems. We recommend use of the form factors and models in this ecosystem and in similar ones for stand and tree volume estimation. 相似文献
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Additional information concerning the quality of growing stock in forests has been obtained for the first time in Baden-Württemberg and Rheinland-Pfalz during the course of Germany’s second national forest inventory (BWI 2; conducted during the period 2001–2002). In this article, the quality assessment—called stem quality rating method—is described with a special focus on its potential to provide the basis for a more detailed investigation of the growing stock’s quality distribution. As a main result, the article presents and illustrates a model-based quantification of single tree and stand/site variable effects on the quality distribution of Norway spruce. Single tree variables showing a significant effect are diameter at breast height (DBH), height–DBH-ratio (h/d-value), age and distance to forest edge. Additional stand/site variables which have a significant effect are altitude, terrain slope, stand type and inventory team. Due to the ordinal type of the response variable, a categorical regression model is applied. Non-linear effects of predictor variables were detected and modeled by integration of smoothing spline terms. Validating model predictions with regard to expert knowledge in forestry led to the integration of simple constraints in the linear predictor, which controls whether category-specific effects are fitted or not. The resulting model could be described as a vector generalized additive non-proportional odds regression model. This improved insight into the determination of stem quality could be applied in optimization studies to derive optimal silvicultural treatments and in the setting up of management guidelines. Assuming constant relationships between predictor and response variables over time, the combined application with growth simulators allows for a prediction of future joint quality and size class assortment distributions. Finally, the model would allow for a sustainability control of stem quality over time if a consecutive inventory will be conducted during the course of the third German national forest inventory (BWI 3). 相似文献
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An annual individual tree survival and growth model was developed for pure even-aged stands of maritime pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering thinning effects. The model is distance-independent and is based on a function for diameter growth, a function for height growth and a survival function. Two approaches are compared for modeling annual tree growth. The first approach directly estimates a future diameter or height using well-known growth functions formulated in difference form. The second approach estimates diameter or height using a function in differential form estimating the increment over a year period. In both approaches, the function parameters were related to tree and stand variables reflecting the competition status of the tree as well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling approaches. An iterative method was used to continuously update tree and stand attributes using a cut-off to convert the survival probability for a living or a dead tree. The individual tree diameter growth model and the survival probability model were fitted simultaneously using seemingly unrelated regression (SUR). Parameters of the height function were obtained separately as the number of observations for height was much lower than the number of observations for diameter, which may affect the statistical inference and the estimation of contemporaneous cross-equation error correlation inherent to the system of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the height growth functions. Additional statistics based in the log likelihood function and also in the survival probability were computed to evaluate the survival function. The second modeling approach, which integrates components of growth expansion and decline, performed slightly better than the first approach. A variable accounting for the thinning response that was tested proved to be significant for predicting diameter growth, even if the model already included competition-related explanatory variables, namely the basal area of trees larger than the subject tree. However, this thinning response factor was not significant for predicting height growth. 相似文献
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Fernando Castedo-Dorado Ulises Diéguez-Aranda Juan Gabriel Álvarez-González 《Annals of Forest Science》2007,64(4):453-465
A dynamic whole-stand growth model for radiata pine (Pinus radiata D. Don) stands in north-western Spain is presented. In this model, the initial stand conditions at any point in time are defined by three state variables (number of trees per hectare, stand basal area and dominant height), and are used to estimate total or merchantable stand volume for a given projection age. The model uses three transition functions derived with the generalized algebraic difference approach (GADA) to project the corresponding stand state variables at any particular time. These equations were fitted using the base-age-invariant dummy variables method. In addition, the model incorporates a function for predicting initial stand basal area, which can be used to establish the starting point for the simulation. Once the state variables are known for a specific moment, a distribution function is used to estimate the number of trees in each diameter class by recovering the parameters of the Weibull function, using the moments of first and second order of the distribution. By using a generalized height-diameter function to estimate the height of the average tree in each diameter class, combined with a taper function that uses the above predicted diameter and height, it is then possible to estimate total or merchantable stand volume. 相似文献
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基于RS的闽江流域马尾松林分蓄积量估测模型研究 总被引：10，自引：0，他引：10
从福建省第5次森林资源一类调查落在闽江流域的样地中抽取马尾松林样地130个,以RS可提取因子及样地林分立地条件因子为可选变量,利用3倍标准差法进行异常数据的筛选,对林分立地条件定性因子进行数量化处理,通过逐步回归构建闽江流域马尾松林分蓄积量估测模型,研究结果所构建的蓄积量估测模型的相关系数为0.735。经模外抽取30个样地对估测模型适用性检验和精度验证表明,在可靠性α=0.01条件下模型估测值与外业实测值无显著差异,模型的林分蓄积量估测精度达85.03%,为此,本研究的蓄积量估测模型对森林经营管理具有现实意义。 相似文献