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1.
曾伟生 《林业科学》1996,32(3):269-273
从“密度指数与林分测树因子数学模型”所存在的问题出发,对林分密度指数与断面积,平均直径和株数之间的关系模型从数学上进行了推导,提出了正确的参数估计方法,并就拟合数学模型应注意的两个问题,即互为自(因)变量问题与参数一致性估计问题进行了综合讨论。  相似文献   

2.
【目的】毛竹立地质量评价是揭示毛竹生长与其立地因子间的关系的重要方法,对其进行研究是科学培育毛竹林的基础。【方法】对福建省永安市毛竹林的胸径、竹高进行了大样本调查分析,采用引入哑变量分级的方法,建立了毛竹的竹高-胸径曲线模型;探讨了毛竹胸径与其立地的气候因子、地形地貌因子及土壤因子间的关系,构建了回归模型。【结果】1)拟合毛竹竹高-胸径曲线的最优模型为逻辑斯蒂模型,引入哑变量分级的方法可以显著提高模型精度。引入哑变量分级的方法与未分级的方法相比,分级后模型的决定系数由0.548提高到0.901。依据模型实验区毛竹林可以分为5个立地等级。2)主成分分析表明,实验区影响毛竹生长的最重要气候因子为1月均温和出笋期降水量。3)对福建省毛竹胸径起影响的地形地貌因子重要性排序为:土层厚度坡位。可以用线性模型拟合胸径-地形地貌因子线性模型:D=0.119×(Pos)+0.803×(Thc)+8.136(R~2=0.554)。4)在土壤因子中,重要性排序为:全氮有机质碱解氮。【结论】采用引入哑变量分级的方法可显著提高毛竹立地质量评价的精度,1月均温、出笋期降水、土层厚度、坡位、坡度、全氮、有机质、碱解氮是与毛竹生长相关的主要气候和立地因子。研究结果为毛竹立地质量评价及生产潜力预估模型的构建提供了新的方法。  相似文献   

3.
在森林资源调查中应用数量化回归估测方法的误差估计   总被引:1,自引:0,他引:1  
在森林资源调查中,我们可以根据某些容易确定的辅助因子来估计需要调查的主要因子。当这些辅助因子中有一些是“不可计量”的因子(例如树种,立地指数等),而主要因子是“可计量”的因子(例如蓄积量)时,就可以采用“数量化回归估测方法”。这种方法是根据林业调查的特点,按数量化方法I所设计的一种等权抽样模型。本文将简单介绍这种模型和适用于这种模型的误差估计公式。  相似文献   

4.
含地域和起源因子的马尾松立木生物量与材积方程系统   总被引:1,自引:0,他引:1  
【目的】建立含地域和起源因子的相容性立木生物量与材积方程系统,为准确估计森林生物量提供依据。【方法】以我国南方主要针叶树种马尾松为研究对象,基于301和104株样木的实测地上生物量、树干材积和地下生物量数据,综合利用哑变量建模方法和误差变量联立方程组方法,建立集地上生物量、树干材积和地下生物量为一体、确保与生物量转换因子和根茎比等变量相容的一元和二元方程系统,并分析立木生物量和材积估计是否受地域和起源的影响。【结果】所建立的马尾松一元和二元相容性立木生物量方程与材积方程,确定系数(R~2)均在0.92以上,其中地上生物量方程的平均预估误差在4%以内,地下生物量方程的平均预估误差在8%以内。对马尾松地上生物量和树干材积的估计,二元模型均显著优于一元模型,其F统计量远大于临界值;但对地下生物量的估计,二元模型反而不如一元模型效果好。不论是一元模型还是二元模型,地域和起源对马尾松地上生物量估计均无显著影响,地上生物量模型具有很好的通用性,同时也进一步印证了曾伟生等(2012)提出的通用性地上生物量模型M=0.3ρD~(7/3)的广泛适用性。对马尾松地下生物量的估计,不同地域的模型存在显著差异;相同直径的林木,总体1地域范围内(长江流域东南部)的地下生物量要大于总体2(长江流域中西部)。对马尾松树干材积的估计,二元模型不受地域和起源影响,但一元模型受起源影响;相同直径的林木,人工林的材积估计值大于天然林。【结论】将哑变量引入误差变量联立方程组,可同时解决多个变量之间的相容性及地上生物量和地下生物量样本单元数不相等时如何联合建模的问题,是切实可行的生物量建模方法;研究所建立的马尾松立木生物量方程、材积方程及其相容的生物量转换因子和根茎比方程,达到相关技术规定预估精度要求,可推广应用。  相似文献   

5.
达摩麝凤蝶是一种亟待保护的珍惜濒危物种,然而目前我们对其自然资源的分布状况了解十分匮乏,只有零星的野外数据,这对于达摩麝凤蝶的保护工作十分不利。因此,通过物种分布模型来预测其潜在适生区是掌握其自然资源分布的有效手段。同时,达摩麝凤蝶与贯叶马兜铃(濒危物种)之间存在特异性寄生的关系。这种强种间相互作用在以往的物种分布模型研究中往往被忽视,但近来一些研究表明,种间关系在对有强烈相互作用的物种进行分布预测时可能是非常重要的影响因子。因此种间关系在达摩麝凤蝶的适生区预测中可能是不可忽略的因子。本文使用最大熵模型(MaxEnt),设置了Ma(仅考虑非生物因子)、Mb(仅考虑种间关系)、Mc(寄主植物的潜在分布)和Md(同时考虑非生物因子和种间关系)4个模型对达摩麝凤蝶的适生区进行了预测,并对Md模型使用通径分析量化非生物因子和种间关系因子对达摩麝凤蝶潜在适生区的影响。结果显示,各模型的预测精度都较高(AUC>0.9),考虑了种间关系的2个模型拟合结果表现较好(AIC:Ma>Mc>Md>Mb)。加入种间关系后得到的分布区面积明显缩小(高适宜区面积:Ma>Mc>Mb>Md)。刀切法结果表明,种间关系在预测中的贡献率最高。通径分析结果表明Mc模型(即种间关系)对Md模型预测的直接通径系数(0.578)和决策系数(R 2=0.546)均为最高。综上所述,种间关系是达摩麝凤蝶潜在分布最主要的影响因子,其在达摩麝凤蝶的适生区预测中有不可忽视的影响。  相似文献   

6.
为更准确地核算小尺度生态足迹,在“全球公顷”和“国家公顷”的基础上建立了“城市公顷”模型,并阐述了在“城市公顷”基础上均衡因子和产量因子的计算方法。通过对池州市市域范围内各类土地的均衡及产量因子的测算,结果表明:计算出的因子数值与“全球公顷”和“国家公顷”模型下的数值存在较大差异,但更能准确客观的表达池州市的实际情况,存在的差异是合理的;通过比较,“城市公顷”模型方法更适合城市级的生态足迹以及生态承载力的核算,相对误差较小。  相似文献   

7.
【目的】建立华北暖温带华北落叶松与白桦针阔混交林树高与胸径关系的非线性混合效应模型,为研究针阔混交林中不同树种相互作用及其生长发育规律提供科学依据。【方法】以河北省塞罕坝机械林场的华北落叶松与白桦针阔混交林为研究对象,基于83块30 m×30 m的标准地调查数据,首先选取5个具有生物学意义的非线性树高与胸径关系基础模型进行拟合,确定最优基础模型;其次通过相关分析确定影响树高生长的主要因子;最后基于最优基础模型和主要因子建立包含哑变量的华北落叶松与白桦针阔混交林树高与胸径关系预测模型。【结果】在5个候选非线性树高与胸径关系模型中,Richard模型具有最好的拟合结果,其模型确定系数(R2=0.918 6)最大,均方根误差(RMSE=2.405 8)及绝对误差(Bias=0.194 5)最小;通过相关分析确定海拔和林分断面积与树高生长均在P 0.01水平上呈现显著性;基于基础模型构建了包含哑变量及主要影响因子的不同树种树高与胸径关系混合效应模型,当随机效应参数作用在林分断面积上时,模型预测精度较高。【结论】基于主要影响因子和包含哑变量的非线性混合效应树高与胸径关系预测模型,能够有效解决混交林中树种及主要因子对树高与胸径关系的影响,提高了预测模型的适用性及预测精度,为混交林森林质量精准提升提供科学依据。  相似文献   

8.
用简单相关分析、偏相关分析、通径分析和多元逐步回归等不同方法分析四季柚净光合速率与多元相关变量间的关系,并用多元逐步回归分析了生理生态因子间的相互关系.结果表明:多元逐步回归方法最优.通径分析次之;影响净光合速率的因子主要是气孔导度、胞间CO2浓度、叶面水汽压亏缺和光照.  相似文献   

9.
林木生物量模型研究评述   总被引:15,自引:0,他引:15  
森林生物量是森林生态系统的最基本特征,要获得准确的森林生物量数据,目前世界上流行的方法是生物量模型估计方法。本文就常用的对数模型和相对生长模型、模型变量的选择以及模型的应用范围等进行了述评。  相似文献   

10.
基于Landsat 8影像的乔木林地上生物量估算   总被引:1,自引:0,他引:1  
以浙江省内的一景Landsat 8影像和96块野外调查数据为数据源,提取出植被指数、纹理特征、地形因子并进行优选,对优选后的变量因子进行分组,生成植被指数、植被指数+纹理特征相结合的2种自变量集,采用偏最小二乘回归法构建乔木林地上生物量估算模型,并对估算结果进行对比分析。结果显示:在构建的模型中,植被指数+纹理特征集构建的模型精度均要优于植被指数集构建的模型,说明多光谱波段的纹理特征具有改善模型估算效果的作用。采用的变量筛选方法较好地考虑了变量间的相关性及共线性问题,可以提高所构建模型的稳定性。  相似文献   

11.
通过建立单木生长模型、林木枯死模型和林分生长模型来模拟闽粤栲天然林生长规律,结果表明:用这3个模型对所调查样地内林木蓄积进行预测,作为林木蓄积量理论计算值,以二元材积表查表得到的蓄积量作为林木蓄积量的实际值,其精度可达94.15%。这些模型对于模拟闽粤栲天然林的生长规律具有一定的应用价值。  相似文献   

12.
林分生长与产量模型系统研究综述   总被引:13,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   

13.
Mabvurira  Danaza  Maltamo  Matti  Kangas  Annika 《New Forests》2002,23(3):207-223
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   

14.
毛竹混交林林分生长状况和结构特征研究   总被引:3,自引:0,他引:3  
对福建省建阳交溪毛竹阔叶树混交林、毛竹杉木混交林、毛竹杉木阔叶树混交林及毛竹纯林等6种不同混交模式林分生长状况进行比较,结果表明:混交林毛竹个体生物量、毛竹胸径和竹高较大,不同模式林分间的胸径、竹高、冠幅等生长因子均达显著差异;竹阔混交林较有利于竹鞭孕芽发笋;各模式竹林结构综合评判为一般经营竹林;竹林竹鞭长、鞭径、鞭节生长以竹阔比例为5:5林分竹鞭较好。  相似文献   

15.
Growth and yield modeling has a long history in forestry. The methods of measuring the growth of stand basal area have evolved from those developed in the U.S.A. and Germany during the last century. Stand basal area modeling has progressed rapidly since the first widely used model was published by the U.S. Forest Service. Over the years, a variety of models have been developed for predicting the growth and yield of uneven/even-aged stands using stand-level approaches. The modeling methodology has not only moved from an empirical approach to a more ecological process-based approach but also accommodated a variety of techniques such as: 1) simultaneous equation methods, 2) difference models, 3) artificial neural network techniques, 4) linear/nonlinear regres-sion models, and 5) matrix models. Empirical models using statistical methods were developed to reproduce accurately and precisely field observations. In contrast, process models have a shorter history, developed originally as research and education tools with the aim of increasing the understanding of cause and effect relationships. Empirical and process models can be married into hybrid mod-els in which the shortcomings of both component approaches can, to some extent, be overcome. Algebraic difference forms of stand basal area models which consist of stand age, stand density and site quality can fully describe stand growth dynamics. This paper reviews the current literature regarding stand basal area models, discusses the basic types of models and their merits and outlines recent progress in modeling growth and dynamics of stand basal area. Future trends involving algebraic difference forms, good fitting variables and model types into stand basal area modeling strategies are discussed.  相似文献   

16.
林分生长和收获模型研究进展   总被引:8,自引:3,他引:5       下载免费PDF全文
文中介绍了全林分模型、径级模型和单木模型3种林分生长和收获模型的特点及国内外应用情况,并提出近几年的发展趋势.  相似文献   

17.
18.
长白落叶松是辽宁省主要造林树种之一,其总体质量关系到辽宁省的生态环境建设。文章根据辽宁省森林资源连续清查数据主要调查因子,基于103块调查样地建立林分生长模型,分析林分生长规律。关于模拟林分生长模型,经典的线性模型往往未能解释数据的离散部分;然而,一些离散变量真正影响林分生长。文中将林分生长特性和林木材积的关系作为一个案例研究,通过分析属性,提出了用广义线性模型分析林分生长数据。  相似文献   

19.
  • ? Simulation tools, based on individual tree growth and mortality models can produce the most detailed predictions of forest stand development under different management schedules. These models allow the manager to predict the development of any type of stand (even- and uneven-aged, and pure and mixed stands).
  • ? Different model approaches and predictors are required for pure even-aged or mixed uneven-aged forest stands. This study developed and compared two sets of models which enable tree-level simulation of the development of pure and mixed stands of Pinus brutia in north-east Greece. The first set of models for even-aged forestry consists of site index models, diameter growth models, tree height models, and mortality models. The second set, which is for uneven-aged forestry, uses a past growth index instead of a site index.
  • ? The simulations and overall fitting statistics suggest that the two types of models provide realistic and accurate predictions of forest stand development and allow one to simulate the development of complex Pinus brutia stand structures in Dadia National Park forests.
  • ? The advantages of the two approaches are discussed and it is suggested that the growth index is an effective predictor of site quality and the set of models which used such variable as predictor performed in a similar way as the models using site index, which require more information and a given stand structure (even-aged).
  •   相似文献   

    20.
    Korean larch(Larix olgensis) is one of the main tree species for afforestation and timber production in northeast China. However, its timber quality and growth ability are largely infl uenced by crown size, structure and shape. The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots, but crown dynamic models has seldom been constructed. Therefore, this study aimed to develop height to crown base( HCB) and crown length( CL) dynamic models using the branch mortality technique for a Korean larch plantation. The nonlinear mixed-effects model with random effects, variance functions and correlation structures, was used to build HCB and CL dynamic models. The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China. The results showed that HCB progressively increases as tree age, tree height growth(HT growth) and diameter at breast height growth( DBH growth).The CL was increased with tree age in 20 years ago, and subsequently stabilized. HT growth, DBH growth stand basal area( BAS) and crown competition factor( CCF) signifi cantly infl uenced HCB and CL. The HCB was positively correlated with BAS, HT growth and D BH growth, but negatively correlated with CCF. The CL was positively correlated with BAS and CCF, but negatively correlated with D BH growth. Model fi tting and validation confi rmed that the mixed-effects model considering the stand and tree level random effects was accurate and reliable for predicting the HCB and CL dynamics. However, the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation, and the fi tting precision of the models was reduced. Therefore, from the point of view of application, we should take care to avoid setting up over-complex models. The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.  相似文献   

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