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1.
《Southern Forests》2013,75(4):201-208
For many years foresters have been using statistical probability density functions to describe and characterise stand structure. Predicting the current and future yields of a stand is essential for successful stand and timber management. Implicit prediction of current yield is accomplished by using diameter distribution methods. All diameter distribution yield systems predict the number of trees per unit area by diameter class. In this study, the normal, lognormal and the three-parameter Weibull probability density function were compared to characterise the diameter distributions of Sal (Shorea robusta) plantations grown at Tilagarh Eco-park, Bangladesh. Data from 70 plots, established in three plantations, were used for this study. The Weibull parameters were estimated by the maximum likelihood and moments estimator methods. A one-sample Kolmogorov–Smirnov test was used for the goodness of fit for all models. The Kolmogorov–Smirnov test results showed that both lognormal and Weibull distributions were suitable to characterise the diameter distributions of Sal plantations in the study area and may be applicable for other Sal forests in Bangladesh. 相似文献
2.
《Scandinavian Journal of Forest Research》2012,27(1-4):493-502
The three‐parameter Weibull function met specified statistical standards for goodness of fit as a model for the diameter distribution of moderately thinned Norway spruce stands in Denmark. Weibull distributions estimated by percentile estimators fit the majority of 522 observed diameter distributions (material made available by the Danish Forest Experiment Station) at the 10% level of significance in the Chi‐square and Kolmogoroff‐Smirnow tests. The Weibull distribution was less suited to describe the diameter distribution in unthinned stands and heavily thinned stands. Weibull parameter predictions were developed and used in connection with a Danish yield table for Norway spruce on clay‐rich coastal soils. The use of the Weibull distribution to predict stem frequencies in different diameter classes before and after a specified thinning of stands is demonstrated. 相似文献
3.
The main purpose of the present investigation is to examine and compare three methods for diameter distribution modeling in
terms of their fitness to predict from stand level variables the diameter distributions of even-aged Austrian black pine (Pinus nigra Arn.) plantations in Bulgaria. The percentile-based projection method involving empirical probability density function based
on 12 percentiles was the first method tested. A new modified approach based on the first method was proposed as the second
alternative. The third method was the 2-parameter Weibull functional model in which parameters were recovered from the first
and the second raw moments and the second central moment of the empirical distributions. The Kolmogorov–Smirnov test was applied
to compare the experimental distributions with the predicted ones, and estimation of the error indices was employed to evaluate
the total absolute deviation of the predicted numbers from the actual ones by diameter class. The two-parameter Weibull function
proved superior to the examined alternative percentile-based projection methods and the newly proposed percentile method,
without a driver percentile showed improved precision compared to the classical percentile method (with a driver percentile).
The parameters of the Weibull frequency distribution function can be easily recovered from the stand quadratic mean diameter.
Consequently, this diameter distribution model could be incorporated as a sub-model for stand horizontal structure characterization
within the Stand Density Management Diagram modeling framework. 相似文献
4.
以峰度、偏度和变动系数为指标研究了辽东山区天然次生林直径株数分布特征。运用Johnson’s SB分布、Gamma分布、3参数和2参数Weibull分布等4种概率密度函数研究了辽东山区天然次生林直径株数分布规律,同时利用Kolmogorov-Smirnov(KS)检验法来检验4种概率分布的拟合效果,结果表明:林分直径的株数分布以Johnson’s SB分布拟合效果最好,Weibull分布(包括2参数和3参数)仅仅适合中度区和弱度区,但不是最好。所有的分布模型均通过了优势度检验,说明均适用于直径株数分布的拟合。 相似文献
5.
现实异龄林分最佳直径分布模型的探讨 总被引：3，自引：0，他引：3
施灵栋 《内蒙古林业调查设计》2006,29(2):50-52
根据在林业中已应用的直径分布模型的统计特征,选择适宜于异龄林分直径分布模拟的指数分布、韦布尔分布、贝塔分布模拟现实异龄林分直径分布。结果表明,对于现实经营林分,由于直径分布不连续、左偏等原因,韦布尔分布模拟效果最好,贝塔分布次之,指数分布最差,这表明现实林分距理想林分还有较大差距。 相似文献
6.
青石冈林场木荷直径结构研究 总被引：1，自引：0，他引：1
以湖南青石冈林场木荷人工林为研究对象,分析了木荷直径结构规律。运用威布尔分布(Weibull)、正态分布、对数正态分布和伽马(Gamma)分布进行直径拟合,并结合X2对拟合结果进行检验,结果表明:木荷林分平均胸径为10.4cm,在5.1～37.1cm之间变动,全距32.0cm,径阶分布范围不大;小径阶的林木数量居多(6～12cm),累计百分比已达到83.7%;4种分布函数中,威布尔分布拟合效果最好,其次是对数正态分布,但两者的差异不大,均可用于预测木荷林直径结构。 相似文献
7.
广东省针阔混交林直径分布规律研究 总被引：1，自引：0，他引：1
基于2012年广东省森林资源连续清查样地和样木调查数据,分析广东省针阔混交林直径分布特征,应用Weibull分布函数分别按全林分、不同起源、不同龄组和不同林分密度对省域尺度的针阔混交林林木直径分布进行了拟合和卡方检验。结果表明,在SPSS和Matlab软件中拟合出的15个模型中有10个能够较好地由Weibull分布函数模拟,多模型较好地表达了起源、龄组、林分密度等主要林分因子的针阔混交林林木直径分布。但纯天然起源、人工植苗、幼龄林、中龄林、林分密度为1 000~1 500株/hm2和2 000~3 000株/hm2的针阔混交林林木直径分布模型因受人为干扰,Weibull拟合效果不理想,需进一步尝试其它抗干扰模型。 相似文献
8.
【目的】以河南登封林场栓皮栎人工林为研究对象,研究抚育间伐对林分不同生长阶段林木株数、林木直径分布和树高分布的影响,为制定科学合理的抚育经营措施奠定理论和技术基础。【方法】在株数强度为31.55%的间伐林分和条件基本一致的未间伐林分内,分别设置1个1 hm2样地,间伐作业2 a后获取每木检尺数据,分别利用Normal分布、Gamma分布、Lognormal分布、Weibull分布、Logistic分布函数对间伐样地和对照样地栓皮栎人工林林木个体直径分布、树高分布进行拟合,并应用Kolmogorov-Smirnov(KS)拟合优度检验,选择拟合效果最好的分布模型。【结果】1)间伐和对照样地幼树、小树和大树林木株数比例分别是9:642:582和229:978:585。相比对照样地,间伐样地林木小树和大树生长阶段株数比重较高。2)间伐样地林木直径分布范围主要集中在8~18 cm,高于对照样地的4~16 cm。KS拟合优度检验结果表明,间伐样地林木直径分布采用Weibull分布拟合效果最好,Normal和Logistic分布次之;对照样地林木直径分布采用Weibull分布拟合效果最好,Normal和Gamma分布次之。3)间伐样地和对照样地林木树高级分别为8~16 m和4~14 m,但KS拟合优度检验结果表明,5种分布函数对间伐样地和对照样地树高分布拟合优度排序一致,说明抚育间伐对林分树高分布的影响不明显。【结论】抚育间伐调整了栓皮栎人工林林分的直径结构,林分直径分布向较大径阶方向偏移,使林分直径分布结构更趋于对称分布,但对树高分布影响不明显。 相似文献
9.
对Richards等6种生长方程的数学解析性及其应用于杉木人工林林分直径结构模拟的理论依据进行了分析和探索,并应用此6种生长方程模拟了林分直径累积分布。发现在描述林分直径累积分布时,Richards方程绝大多数表现为Logistic型,Weibull方程的参数c均大于1,曲线存在拐点;除Mitscherlich式外,各生长方程的模拟精度均相当高,Richards、Weibull、Logistic、Gompertz、Mitscherlich、Kod等6种生长方程样本选优率依次降低;Richards、Logistic、Weibull、Gopertz、Korf及Mitscherlich等6种生长方程总体模拟精度依次降低;相对生长率表现为变量指数函数方程的精度较相对生长率表现为变量幂函数方程的精度高,且3参数方程的精度较2参数的高。 相似文献
10.
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. 相似文献