一个考虑水分影响的森林生长机理模型

文章介绍了林分生长模型GOTILWA+。该模型基于单株林木生长过程,采用光合作用模型等模型的机理模拟树木的生理过程,从而计算林分生长。该模型具有较为广泛的适用范围,是一个较为方便的可科模拟预测气候变化条件下林分生长和森林碳循环的科学工具。     

组合模型在林木生长规律研究中的应用

建立生长模型是研究林木生长规律的有效手段。本文阐述了组合模型建立的原理与方法 ,并以实例介绍林木生长组合模型的建立 ,结果表明 :基于线性规划理论求解组合模型的权重所建的模型精度高于构成它的单一模型精度。     

用二类调查样地建立落叶松单木直径生长模型

根据来自吉林省汪清林业局二类调查的１４个落叶松固定样地的３４６株复测林木数据,建立了与我关的落叶松木平方直径生长最模型。它包含了单木直径生长模型所需考虑的林木大小,立地条件和林木竞争这３个因素,并具有与年龄、地位指数无关的特点,便于实践中应用,逐步回归的结果表明,落叶松单木平方直径生长最模型需要考虑的主要因子是林木直径值、林分断面积和坡度。     

高海拔地区林木年轮生长温度敏感性分析

由于分析林木年轮生长规律是完善模拟生态系统的重要方式,为了进一步掌握林木年轮生长的规律与相关影响因素,以高海拔地区林木为例,对其年轮生长温度敏感性展开了分析。通过选择研究样本,并对高海拔地区林木年轮主要特征进行了描述,探讨了林木年轮生长与地区气候相关系数、地区平均气温、地区年平均降雨量等要素之间的关系。以此为依据,研究了林木年轮生长序列与温度敏感度的一致性规律,得出了高海拔地区林木年轮生长与温度呈现一定关系的结论。     

水曲柳单木生长模型的研究

根据黑龙江省、市、县576块水曲柳固定样地的解析木数据,在水曲柳单木直径生长模型中引入林木大小、竞争和立地条件因素,采用回归的方法建立水曲柳单木直径生长模型。研究表明：水曲柳单木生长模型与该林木自身的大小（lnD）、林分平均胸径（Dg）、对象木直径与林分中最大林木直径之比（DDM）以及土壤有较大的关系。林木的直径越大其生长量越大;竞争因子DDM说明水曲柳单木直径越大;其定期生长量越小;立地因子土壤表明,土层越浅其生长的越快。模型的检验精度为94%,说明模型具有良好的拟合效果,可用于实际的生产中。     

林木生长叠合模型

本文阐述了叠合模型的基本原理与方法,并以林木优势高生长模型为例,详细介绍了叠合模型在模拟林木生长过程中的应用。结果表明叠合模型优于一般生长模型。     

北京地区侧柏人工林单木胸径生长模型的研究

生长模型是研究树木生长过程和进行森林经营管理中常用的工具。使用4期北京市侧柏人工林一类清查共计26个样地、1 172株单木数据建立了3个胸径生长模型。模型自变量选用了林木生长、立地条件和林木竞争3类因子,在建模过程中剔除了出现严重多重共线性问题的自变量,使用逐步回归方法所建的3个模型均通过了方差分析、方差齐性和残差正态性检验。使用检验数据对模型进行T检验,结果表明实际值和预测值差异不显著,即所建立的3个单木模型具有良好的预测效果。     

望天树人工林林木个体前期生长节律的研究

依据20年生望天树人工林林木的生长调查及平均木的树干解析材料,分析了其林木个体的胸径、树高和材积的生长过程和规律,结果表明:在其人工林中望天树林木的前期生长迅速,20年生时林木个体的带皮胸径、树高和带皮材积分别达到19.4 cm,19.8 m和0.298 m3。其相应的年均生长量分别达到0.97 cm、0.99 m和0.0149 m3;望天树林木个体的胸径、树高和材积生长在6年生前较为缓慢,至14年生左右达到高峰,此后呈下降的趋势。依此,建立了望天树人工林林木个体的胸径、树高、材积生长模型。     

拟南芥在林木分子生物学研究中的应用

从分子水平上研究和调控林木生长发育是林木生物技术发展的新趋势,然而由于林木作为研究材料的局限性,如难以在实验室操作和较长的生长周期等,大大阻碍了林木分子生物学的研究.拟南芥是植物学研究中最重要的模式植物,是进行植物分子生物学研究的极好材料.近年来的研究表明,草本植物拟南芥不仅可以为林木分子育种提供基因资源,还可以作为林木分子生物学研究的辅助手段,甚至可以直接作为林木发育分子机理研究的实验模型.本文重点讨论拟南芥在研究林木材质形成、生殖生长和休眠等独特生理规律上的重要价值,在此基础上提出合理运用拟南芥模型,结合林木本身的特点,建立林木与拟南芥的联合研究体系,是开展林木分子生物学研究的重要思路.     

序列林价及其在林木资源资产评估中的应用

【目的】以浙江省龙泉市杉木用材林为例,建立科学、实用的林木资源资产评估模型,使之能够应用于非交易性森林资源资产业务中的小班林木资源资产评估实践,如林权抵押贷款、森林保险、林木生物资产核算等领域中的大批量小班的林木资源资产评估。【方法】设定参照林分,引入生产函数理论,建立参照林分的生长模型;研究相邻年度林木价值关系,设计序列林价递推公式;分析林分林木资产价值主要影响因素,构建基于序列林价的小班林木资源资产评估模型,并对林木资产评估模型进行适用性检验,包括模型估算值与样本实际值的差异显著性检验和模型使用精度检验。建模过程中综合运用了递推算法、回归方法、仿真模拟方法。【结果】编制杉木林参照林分序列林价表,该表能够客观反映出林木价值生长过程;拟合林价主要影响因素调整系数模型参数,给出小班集材路程调整系数经验模型,以及成熟林小班的林分平均胸径调整系数经验模型、单位面积蓄积量调整系数经验模型;应用小班林木资产评估模型进行龙泉市岩樟乡芭蕉村杉木用材林小班林木资源资产评估,计算得到杉木用材林小班林木资产明细表,经汇总得到各农户杉木用材林林木资产价值、全村杉木用材林林木资产价值;利用98个正常交易实例检验样本计算小班林木资产评估模型检验指标,总相对误差-0.16%、平均相对误差1.25%、平均相对误差绝对值8.97%,估计精度97.6%,全部检验指标均符合要求。【结论】基于序列林价的小班林木资源资产评估模型结构化、直观、可理解,评估效果较好,能够适用于非交易性森林资源资产业务中的大批量小班的林木资源资产评估业务;引入生产函数理论,保证参照林分营林过程中投入与产出的匹配性;序列林价递推算法可以更好地研究林分完整生长过程中的序列林价变化规律,实现重置成本法、收益现值法、市场价倒算法3种方法的融合与相互验证;通过林龄价值系数可以实现参照林分序列林价更新、小班林木资产评估模型更新;建立林价主要影响因素调整系数回归模型,优于以往对影响因素作分级处理的简单做法。     

广西速丰桉林分二元材积生长率表研制

速丰桉一年四季生长,没有明显年轮的特征,难以对单株木进行树干解析确定林木生长量。在没有足够数量的固定标准地连续定期监测数据的情况下,采取临时标准地年龄序列的调查方法,选用适当模型结构,再通过引进可变参数改进生长模型,建立以年龄、胸径为基础的林分材积生长率模型,并编制广西速丰桉林分二元材积生长率表。经检验,方法可行,预估精度满足林业数表建模要求,可应用于速丰桉林材积生长量的预估。     

Finding the appropriate level of complexity for a simulation model: An example with a forest growth model

The topic of model complexity is fundamental to model developers and model users. In this study, we investigate how over- and under-fitting of a driving function in a simulation model influences the predictive ability of the model. Secondly, we investigate whether model selection approaches succeed in selecting driving functions with the best predictive ability. We address these issues through an example with the forest simulator SORTIE-ND. Utilizing maximum likelihood methods and individual tree growth data we parameterize five growth functions of increasing complexity. We then incorporate each growth function into the simulation model SORTIE-ND and test predicted growth against independent data. Compared to the independent data, the simplest and the most complex growth functions had the poorest predictive ability while functions of intermediate complexity had the best predictive ability. The poor predictive ability of the simplest model is caused by poor approximation of the system while the poor predictive ability of the most complex model is caused by biased parameter estimates. A growth function of intermediate complexity was the most parsimonious model where error due to approximation and error due to estimation were simultaneously minimized. The model selection criteria AIC and BIC were found to select complex functions that were over-fitted according to the independent data comparison. BIC was closer to choosing the model that minimized prediction error than AIC. In this example, BIC is the more appropriate model selection criterion. It is important that both model developers and models users remember that more complex models do not always result in better predictive models.     

Evaluation of unconstrained and constrained mathematical functions to model girth growth of rubber trees (Hevea brasiliensis) using young age measurements

No attempt has been made to date to model growth in girth of rubber tree (Hevea brasiliansis). We evaluated the few widely used growth functions to identify the most parsimonious and biologically reasonable model for describing the girth growth of young rubber trees based on an incomplete set of young age measurements. Monthly data for girth of immature trees (age 2 to 12 years) from two locations were subjected to modelling. Reparameterized, unconstrained and constrained growth functions of Richards (RM), Gompertz (GM) and the monomolecular model (MM) were fitted to data. Duration of growth was the constraint introduced. In the first stage, we attempted a population average (PA) model to capture the trend in growth. The best PA model wasfitted as a subject specific (SS) model. We used appropriate error variance-covariance structure to account for correlation due to repeated measurements over time. Unconstrained functions underestimated the asymptotic maximum that did not reflect the carrying capacity of the locations. Underestimations were attributed to the partial set of measurements made during the early growth phase of the trees. MM proved superior to RM and GM. In the random coefficient models, both Gf and G0 appeared to be influenced by tree level effects. Inclusion of diagonal definite positive matrix removed the correlation between random effects.The results were similar at both locations. In the overall assessment MM appeared as the candidate model for studying the girth-age relationships in Hevea trees. Based on the fitted model we conclude that, in Hevea trees, growth rate is maintained at maximum value at t0, then decreases until the final state at dG/dt ≥ 0, resulting in yield curve with no period of accelerating growth. One physiological explanation is that photosynthetic activity in Hevea trees decreases as girth increases and constructive metabolism is larger than destructive metabolism.     

辽宁省森林蓄积连年生长率的研究

利用森林资源规划设计调查的数据,以各树种(组)不同林龄的小班集合,计算各树种不同林龄的平均每公顷蓄积量,绘制森林蓄积生长曲线,选择数学模型,得出不同树种的生长规律参数;通过计算不同林龄的理论值,最后得出森林蓄积连年生长率.     

四种针叶低效林单株生长模型构建

以碳汇林基线情景低效针叶林,包括日本落叶松、杉木、马尾松、湿地松为研究对象,利用收集和调查的生物量与解析木实测数据,选择不同数学模型,通过曲线回归、非线性回归方法拟合模型参数,建立4个树种的单株生物量模型、胸径生长模型和树高生长模型。结果表明:4个树种的单株生物量模型、胸径生长模型采用相关系数较高、MSE值最小的幂函数模型、S模型拟合效果最好;4个树种的树高生长模型形式各异,日本落叶松、湿地松以Logistic模型拟合效果最好,杉木以抛物线模型拟合效果最好,马尾松以S模型拟合效果最好;检验结果表明,所建日本落叶松、杉木、马尾松、湿地松的生长模型预估精度均达到了95%以上,且都通过了F检验。     

A state-space approach to stand growth modelling of European beech

Static models of forest growth, such as yield tables or cumulative growth functions, generally fail to recognize that forest stands are dynamic systems, subject to changes in growth dynamics due to silvicultural interventions or natural dynamics. Based on experimental data, covering a wide range of initial spacings and thinning practises, we developed a dynamic stand growth model of European beech in Denmark. The model entailed three equations for predicting dominant height growth, basal area growth, and mortality. The signs of the parameter estimates generally corroborated the anticipated growth paths of dominant height and basal area. Although statistical tests indicated significant systematic deviations between observed and predicted values, the deviations were small and of little practical importance. Cross validation procedures indicated that the model may be applied across a wide range of growth conditions and thinning practises without significant loss of precision.     

Adapting a growth equation to model tree regeneration in mountain forests

Management and risk analysis of protection forests depend on a reliable estimation of regeneration processes and tree growth under different site conditions. While the growth of forest stands and thus the average growth of larger trees is well studied and published in yield tables as well as embodied in numerous simulation models, there is still a lack of information about the crucial initial stages of tree growth. Thus, we evaluated juvenile tree growth for different site conditions in the Swiss Alps and developed an approach to model both the early and later stages of growth based on the Bertalanffy equation. This equation is physiologically well founded and requires only two parameter estimates: a maximum tree height and a growth parameter. Data for the parameter estimation were available from studies of tree regeneration at a range of sites in Switzerland: growth patterns of larch (Larix decidua) were available from a high-elevation afforestation experiment. For spruce (Picea abies), data were obtained from a blowdown area in the Alps. The growth equation was fitted to the observed data and we found a good correlation of the fitted curves with the observed data. The parameter estimates were validated with independent data sets. The extrapolated growth curves, calculated with the estimated growth rates, correspond well to the validation data. Thus, it is possible to use the Bertalanffy equation to model both the early and later stages of growth. With this approach, we provide a basis for modelling the growth of juvenile and mature trees of different tree species in mountain forests of the European Alps.     

大兴安岭东南部兴安落叶松胸径生长率与材积生长率的关系研究

兴安落叶松 ( L arix gmelini,以下简称落叶松 )是大兴安岭林区的主要树种 ,文章研究落叶松胸径生长率与材积生长率的关系 ,建立数学模型 ,使之通过测算胸径生长率来预测材积生长率 ,为简化材积生长量调查提供了理论依据。     

辽宁省东部山区日本落叶松生长差异的研究

利用森林资源规划设计调查的数据成果,分别计算丹东、本溪、抚顺和铁岭4个区域日本落叶松不同林龄的平均每公顷蓄积量,选用Richards方程来建立蓄积生长模型,绘制生长曲线;对4个地区日本落叶松的生长状况进行分析,找出4个地区生长差异的规律,以指导营林生产活动。     

麻城市河滩地意杨早期生长模型及经济效益研究

采用SPSS软件对麻城市河滩地意杨林早期生长数据进行曲线拟合,选定Quadratic曲线作为胸径与年龄的生长模型,Logistic曲线作为树高与年龄的生长模型,并分析了意杨林8年主伐期时的净收益。