基于最小尺度的浙江省毛竹生物量精确估算

以浙江省为例,提出基于最小尺度的区域生物量估算新方法,包含3方面内容:1)利用二元Weibull生存函数推导二元Weibull分布函数,并用二元Weibull分布函数估算浙江省各径阶、各龄级毛竹的总株数;2)利用已有毛竹胸径、年龄二元单株生物量模型f(D,A),计算各径阶、各龄级毛竹的生物量;3)利用公式MT=∑m i=5 ∑n j=1 kijf(Di,Aj) 实现区域尺度生物量的精确估算.用该方法估算得浙江省毛竹总生物量为1.471 6×1010kg.     

四川江安县人工经营毛竹林分结构特征

通过对江安县毛竹人工林的典型样地调查,利用Weibull分布函数对其年龄、胸径和枝下高的密度分布进行了模拟。结果表明:(1)毛竹人工林株数分布较均匀,且结构较合理,1度竹达598株·hm-2,占林地总株数的16.5%;(2)毛竹人工林分的年龄分布符合三参数Weibull分布函数,其所有样地拟合的可决系数R2达0.99812,各年龄组误差均在3%以内;(3)毛竹人工林分胸径和枝下高分布符合二参数Weibull分布函数,其全部样地拟合的可决系数R2分别为0.99951和0.99819;由于人工干扰的原因,其胸径分布的前4个径阶组和枝下高分布的前3个高阶组的拟合误差较大,最大值分别为31.69%和-30.02%,而其余各组的拟合误差则多在3%以下;(4)毛竹人工林的胸径-年龄和枝下高-年龄具有相似的结构特征,即,成熟龄组的胸径分布呈正态分布,对应的竹高分布则呈现左截尾的非完整的正态分布,而其余龄组则无明显分布特征,这与人为经营活动及其水平是相关的。     

关于五常市宝龙店林场主要林分类型直径分布的研究

研究应用五常市地区宝龙店林场调查的20块次生林标准地的数据,分析林分的直径分布规律,运用指数分布、正态分布和Weibull分布函数对其进行拟合,用R语言对样地数据进行处理,建立直径回归模型,用分布检验并比较各种分布函数对实际数据的拟合效果。研究结果表明:随着林分树木直径不断增加,林木株数在总体上呈现出减小的趋势。在人工林中,正态分布和Weibull分布的拟合效果较好;在阔叶林中, Weibull分布拟合效果更好。     

西藏天然林直径分布模型及其应用研究

以西藏自治区2006年森林资源连续清查的479个天然林实测样地资料为基础,利用相对直径和累积概率的概念,借鉴相对树高曲线模型的建模方法,研究建立了冷杉、云杉、柏木、松类、栎类、桦类、阔叶类、针阔类等8个树种（组）的直径分布累积概率模型。通过与常用于天然异龄林直径分布结构的Weibull分布函数的拟合结果进行对比分析,表明所建模型效果良好。所建的直径分布累积概率模型为预估林分直径分布结构提供了参考依据,尤其为2006年西藏森林资源连清遥感样地和目测样地的样木模拟提供了定量依据。     

测树因子二元概率分布:以毛竹为例

应用二元联合熵函数,仿照一元最大熵函数的推导过程,构建测树因子二元最大熵概率密度函数,指出该函数实际上是二元多参数指数族分布,其幂是二维连续函数空间基的线性组合;一元与二元最大熵函数的构建可以得出:这种构建模型的方法可以推广到测树因子二元以上概率分布的情形;对二元最大熵函数与二元Weibull分布模型做对比分析,并指出前者具有更广的适应性;对已有二元函数如二元SBB函数与二元Beta函数做了概述,介绍SBB函数初值选取方法,并指出二元SBB函数能反映2个随机变量的相关程度;用二元最大熵函数、二元SBB函数与二元Beta函数分别测量浙江省域尺度毛竹胸径、年龄联合分布信息,结果表明前2者的测量精度非常高,都适合于描述毛竹胸径、年龄联合分布规律,回归离差平方和、R2与柯尔莫哥洛夫检验统计量依次为9.97677e-05,0.9960,0.99983;0.00084,0.96400,0.97998;二元Beta函数测量精度最低,函数初值选取与变量区间变换还有待于进一步研究。     

庆元县人工杉木林直径分布的研究

利用正态分布、β分布、Г分布、Weibull分布四种概率密度函数研究直径分布规律，分析了四种概率密度函数的拟合效果，探讨了不同年龄、不同地位指数对Weibull分布拟合率的影响，建立了Weibull分布三参数与林分特征因子的回归方程。据此，可编制林分直径分布预估表。     

广东省针阔混交林直径分布规律研究

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。     

用Weibull分布拟合刺槐林分直径结构的研究

应用三参数Weibull分布拟合刺槐林分林木直径分布，并与正态分布及回归方程Y=ae^b(x-x^-)^2拟合结果对比，表明用Weibull分布拟合效果好，精度高，能描述刺槐林分林木直径分布规律，可反映出实际分布与理论分布接近的程度，有一定的现实意义。     

基于Weibull分布的林分结构可视化模拟技术研究

林分结构是林分生长和林分经营的理论基础,具有重要的生产实践和科研价值。以杉木人工林为研究对象,以30 m×30 m样地大小为例,以Weibull分布拟合林分直径结构,并进行x2检验。在已知林木算术平均胸径和林木株数的前提下,以C#语言为基础,结合Weibull分布模型、测树因子间关系模型、生物量估计模型、GDI+技术与MOGRE技术,实现了林分结构统计图表可视化模拟,并对林分进行了2维3维可视化模拟。结果表明:Weibull分布可有效拟合林分直径结构分布,可视化模拟技术使林分结构得到了更加直观高效的表达,为研究林分结构提供了新的技术手段,为提高森林经营管理水平提供了可视化决策平台。     

基于哑变量的湖南栎类次生林直径分布研究

文章以湖南省188个栎类次生林样地为研究对象,利用Kolmoglov-Smirnov检验法对6种分布密度函数在直径分布拟合中的适用性进行检验。以林分变量为自变量,采用参数预测法构建Weibull函数3个参数的逐步回归参数模型和以林分类型为哑变量的哑变量参数模型,并对比两类模型的直径分布预测精度。结果表明,Weibull函数更适合于栎类直径分布的拟合(接受率为91.7%);与逐步回归参数模型相比,参数b、c的哑变量模型的R~2分别提高了0.104和0.134,且应用于直径分布预测时的精度显著提高(P=0.025)。研究基于林分类型哑变量构建参数模型,并用于栎类次生林的直径分布预测,预测精度较高。     

Characterising the diameter distribution of Sal plantations by comparing normal,lognormal and Weibull distributions at Tilagarh Eco-park,Bangladesh

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.     

Comparing normal,lognormal and Weibull distributions for fitting diameter data from Akashmoni plantations in the north-eastern region of Bangladesh

Statistical probability density functions are widely used to model tree diameter distributions and to describe stand structure. The objective of this study was to compare the performance of normal, logarithmic-normal and three-parameter Weibull distributions for fitting diameter data from Akashmoni (Acacia auriculiformis A. Cunn. ex Benth.) plantations grown in the north-eastern region of Bangladesh. Data from 96 plots, established in 24 plantations in north-eastern Bangladesh and ranging in age from 1 to 6 years, were used for this study. The parameters of the Weibull distribution were calculated using maximum likelihood estimation (MLE) and moment estimation (ME) methods. The goodness of fit of normal, lognormal, Weibull MLE and Weibull ME were tested using one-sample Kolmogorov-Smirnov (KS) tests. The KS test results showed that both lognormal and Weibull distributions were equally effective for describing the diameter distributions of these Akashmoni plantations grown in the north-eastern region of Bangladesh.     

浙江遂昌县毛竹低产林成因及改造技术探讨

毛竹是浙江遂昌县竹林资源中分布最广、面积最大的优良经济竹种,但是50%以上毛竹林为低产林,迫切需要进行改造,提高其生产力。文中分析了遂昌县低产毛竹林的成因,提出了相应的改造技术措施,以期全面提升遂昌县低产毛竹林的生产经营水平,并取得良好的经济和社会效益。     

Fitting irregular diameter distributions of forest stands by Weibull, modified Weibull, and mixture Weibull models

Irregular diameter frequency distributions of forest stands include multimodal structure of mixed-species stands, highly skewed and highly irregular shapes of uneven-aged stands, and rotated sigmoid form of old-growth stands. In this study, a traditional two-parameter Weibull model, a modified two-parameter Weibull model, and a finite mixture of two-parameter Weibull models were used to fit four artificial example plots. The model fitting and comparison results indicate that the mixture Weibull model is more flexible to fit various irregular diameter distributions, while the traditional Weibull model fails in every case to adequately describe these frequency distributions. The modified Weibull model is a good choice for fitting the “rotated-sigmoid” diameter distribution of an uneven-aged old-growth stand. However, it may not be sufficient when a diameter frequency distribution is multimodal or highly irregular in shape.     

浙江毛竹林生态经营技术的PRA-DPSIR评价

融合参与式农村评估(PRA)和"驱动力-压力-状态-影响-响应"模型(DPSIR)2种工具,对浙江11个主要毛竹县(市)1 591户竹农的经营技术开展分析评价。结果表明,浙江竹农毛竹经营采伐强度较大、土地负载高、粗放随意;对留笋养竹、立竹保留量、采伐时间和对象、垦复砍杂等通用技术以及作为新兴基础设施的水分管理有待改进,土壤生态化管理和施肥则需要优先考虑。应强化面向农户的应用技术推广,避免急功近利式的经营导向,重视土壤水肥管理基础上的综合措施应用,确保生态可持续前提下的经营产出。     

安徽省毛竹林下植物物种多样性的研究

借以安徽省林业厅与浙江农林大学合作以提升安徽省竹产业的契机,调查安徽省毛竹面积最多的霍山县、广德县、黄山区三县(区)毛竹林下植物物种多样性的情况,以了解和掌握在当前的经营水平下,毛竹林下灌木与草本的数量特征、群落的物种结构特征,并且对如何开发珍稀植物物种进行了探讨.结果表明:毛竹林下灌木主要以株高小于40 cm的蓬藁、紫金牛、山檀、六月雪、山胡椒等为主,草本主要是淡竹叶、中日金星蕨、大油芒等:群落的物种结构特征表现为灌木主要以豆科、蔷薇科、大戟科、壳斗科、樟科为主,草本主要以禾本科、菊科、金星蕨科、百合科、唇形科、豆科等为主.保护毛竹林植物物种多样性,有效利用毛竹林下空间,发展复合经营,对提升毛竹林经营效益有重要意义.     

A New Function for Modelling Diameter Frequency Distribution in the Tropical Rain Forest of Xishuangbanna, Southwest of China

Permanent plots in the montane tropical rain forests in Xishuangbanna, southwest China, were established, and different empirical models, based on observation data of these plots in 1992, were built to model diameter frequency distributions.The focus of this study is on predicting accuracy of stem number in the larger diameter classes, which is much more important than that of the smallcr trees, from the view of forest management, and must be adequately considered in the modelling and estimate.There exist 3 traditional ways of modelling the diameter frequency distribution: the negative exponential function model, limiting line function model, and Weibull distribution model. In this study, a new model, named as the logarithmic J-shape function, together with the others, was experimented and was found as a more suitable model for modelling works in the tropical forests.     

毛竹林可持续经营初步试验

在探索和研究毛竹林可持续经营模式的基础上,利用本地毛竹林资源的优势开展毛竹林可持续经营试验,以防止出现对毛竹资源的过渡消耗,保证毛竹产业化长期、健康、平稳发展,同时为产区的毛竹生产经营提供了重要的参考价值。     

Comparison of selected statistical distributions for modelling the diameter distributions in near-natural <Emphasis Type="Italic">Abies</Emphasis>–<Emphasis Type="Italic">Fagus</Emphasis> forests in the Świętokrzyski National Park (Poland)

The aim of the study is to compare selected theoretical distributions (normal, lognormal, Weibull, gamma, logistic, and exponential) in describing the tree diameter (DBH) distributions of mixed near-natural forests consisting of fir Abies alba Mill. and beech Fagus sylvatica L. growing in various vertical structures. Tree DBH data were collected between 1997 and 2008 from 51 sample plots established in the Świętokrzyski National Park in Poland. The empirical data represent differentiated DBH distributions, ranging from almost symmetric to extremely asymmetric ones. The chi-square test and the modified Kolmogorov–Smirnov test were chosen for the goodness-of-fit testing. In addition to the test statistics, the bias (B), the root mean square error (RMSE) and the graphical method (quantile–quantile plots) were used. In one-storied stands, the most suitable distributions were the normal and logistic distributions; in two-storied and multilayered stands, the Weibull and gamma distribution were the most suitable; and in selection stands, the exponential distribution was the most appropriate to describe the DBH distribution. The order of precision of the tested distributions (from the highest to the lowest) was Weibull, gamma, logistic, normal, exponential, and lognormal. The normal and exponential distribution should be applied only to one-storied and selection forests, respectively. The least suitable distribution for DBH distribution modelling was the lognormal one.