GROWTH AND YIELD MODELS FOR DAHURIAN LARCH PLANTATIONS

Growth and yield models were developed for individual tress and stands based on336 temporary plots with 405 stem analysis trees of dahurian larch(Larix gmelinii(Rupr.)Rupr.)plantations throughout Daxing’anling mountains.Several equations were selected using nonlinearregression analysis.Results showed that the Richards equation was the best model for estimatingtree height,stand mean helght and stand dominant height from age; The Power equation was thebest model for prediction tree volume from DBH and tree height; The logarithmic stand volumeequation was good for predicting stand volume from age,mean height,basal area and other standvariables.These models can be used to construct the volume table, the site index table and other for-estry tables for dahurian larch plantations.     

Influence of different forest conversion strategies on ground vegetation and tree regeneration in pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) stands: a case study in NE Germany

The conversion of anthropogenic into more natural, self-regenerating forests is one of the major objectives of forestry throughout Europe. In this study, we present investigations on permanent plots with different silvicultural treatment in NE German pine stands. Management of old-growth pine stands on acidic and nutrient-poor sandy sites differs in fencing, thinning, and planting of certain tree species. The investigations were carried out on the community, population, and individual level of the pine forest ecosystems. Thus, vegetation changes, size and height of tree populations, and height increment of tree individuals were observed over a time span of 6 years. Special attention was paid to short-lived tree species such as, e.g., Frangula alnus and Sorbus aucuparia, as well as to Fagus sylvatica as one of the most typical forest tree species of Central Europe. Vegetation changes are interpreted as a consequence of natural regeneration of formerly degraded forest sites, involving an increase in nutrient availability. High browsing pressure can be considered as a key factor for the inhibition of tree seedlings and growth of saplings. Some Sorbus aucuparia individuals, however, succeeded in growing out of the browsing height also in unfenced stands. Few found specimens of Fagus sylvatica proved that this species is able to establish spontaneously on these relatively dry, acidic sites under continental climate influence. Such natural regeneration processes, also including spontaneous rejuvenation of trees, can be integrated into silviculture as passive forest conversion management. An active management like thinning of stands, planting of trees, and fencing can accelerate forest conversion with regard to height growth and species number of trees.     

A basal area increment model for individual trees growing in even- and uneven-aged forest stands in Austria

Because of the gradual shift from pure even-aged forest management in central Europe, existing yield tables are becoming increasingly unreliable for forest management decisions. Individual tree-based stand growth modeling can make accurate stand growth predictions for the full range of conditions between pure even-aged and mixed-species uneven-aged stands. The central model in such a simulator is basal area increment for individual trees. Spatial information is not needed, and age and site index are intentionally not used to gain generality for all possible stand conditions. A basal area increment model is developed for all the main forest species in Austria: spruce (Picea abies), fir (Abies alba), larch (Larix decidua), Scots pine (Pinus sylvestris), black pine (Pinus nigra), stone pine (Pinus cembra), beech (Fagus silvatica), oak (Quercus robur, Quercus petraea and Quercus cerris), and for all other broadleaf species combined. The Austrian National Forest Inventory provided 5-year basal area increment from 44 761 remeasured trees growing on 5416 forested plots in the 1980s. This large sample is representative of forest conditions and forest management practices throughout Austria and therefore provides an excellent data base for the development of an increment model. The resulting increment model explained from 20 to 63% of the variation for all nine species and from 33 to 63% of the variation if the minor species Pinus cembra is excluded. These results compared quite closely with those of Wykoff for mixed conifer stands in the Northern Rocky Mountains. In the Austrian model, size variables (breast height diameter and crown length) accounted for 14–47% of the variation in basal area increment, depending on tree species. The best competition measure was the basal area of larger trees, which provides a tree-specific measure of competition without requiring spatial information; crown competition factor provided only minor improvement. Competition variables accounted for 9% of the variation on average, and up to 15% for some species. Topographic factors (elevation, slope, aspect) explained up to 3% of the variation, as did soil factors. Remaining site factors; such as vegetation type and growth district accounted for a maximum of 3% of the variation in increment. In total, site factors explained from 2 to 6% of the variation. Even though site factors account for a small percentage of the variation, they are not only significant, but serve to localize a particular prediction. These species-specific interrelationships between basal area increment and the various size, competition, and site varibles correspond quite well with ecological expectations and silvicultural understanding of these species in Austria. Because the sample base is so strong, the resulting growth models can be recommended not only for all of Austria but for surrounding regions with similar growth conditions.     

Distance-independent tree basal area growth models for Norway spruce,Douglas-fir and Japanese larch in Southern Belgium

This paper presents new harmonized distance-independent individual tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in pure even-aged stands in Southern Belgium. The selected model was originally developed for Norway spruce and Douglas-fir in neighboring France. New formulations are proposed for some of the model components in order to lower the number of fitted parameters and facilitate the fitting procedure. The resulting models integrate the most recent corresponding top-height growth models and use four simple and usually collected explanatory variables: stand age, top-height, total basal area and tree girth at breast height. The modified formulations maintain similar fitting performances and make it easier to interpret the influence of the explanatory variables on tree growth. Parameters estimates were fitted on thousands of growth measurements gathered from several monitoring plots, forest management inventories and silvicultural field experiments that represent the wide range of site conditions and of forest management scenarios applied to coniferous stands in Southern Belgium. Cross-validation of the models revealed no bias and highlighted their consistent behavior over the entire range of girth at breast height, age, top-height, site index and density represented in our dataset. Combining utility and robust performances, these models represent useful forest management tools, purposely ideal for forest simulation software development. Moreover, the flexibility and generic capabilities of the model formulation should make it easily adjustable for other species in even-aged stands.     

The study on site quality evaluation for dahurian larch (Larix gmelinii Rupr.)

Site quality of larch (Larix gmelinii Rupr.) in Da Xingan Mountain in Inner Mongolia was studied systematically with about 1000 temporary plots and computer software. The nature of site class and site index curve was discussed in view of general mathematical model of height growth. The height growth of dominant tree of four divisions of forest stands were studied and site index tables were constructed respectively. In order to unify the comparing standard and convenience for management in this region, site index table was constucted too. Based on discussing the action and accuracy of forest type, a series of site quality evaluation (forest type-site index class-site index) was suggested. This subject of study is supported by the National Natural Scientific Fund (No. 39270549).     

基于多水平非线性混合效应蒙古栎林单木断面积模型

以吉林省汪清林业局184块样地中的10 111株蒙古栎为例,首先选用线性函数、Richards函数、Logistic 函数、指数函数等7种常用函数形式,分析4个因变量(后期胸径、后期胸高断面积、直径增量和胸高断面积增量)与前期胸径的影响,确定一个用于构建混合效应模型的基础模型。然后确定同时考虑林场效应和林场与样地交互效应时基础模型中最优的形式参数构造形式,利用逐步回归方法确定模型中所包含的林分变量,并分析和比较用来消除异方差的3种常用残差方差函数(指数函数、幂函数和常数加幂函数),最后检验模型预测效果。结果表明:Wykoff模型且因变量为后期胸高断面积拟合效果较好,故作为基础模型;除前期胸高直径(D)外,当考虑坡度正切(ST),对象木胸高直径与样地算术平均直径的比(RAD),样地胸高总断面积(TBA),样地中大于对象木直径所有树木的胸高断面积和(GSBA),对象木胸高断面积与样地算术平均胸高断面积的比 (RABA)和对象木胸高断面积与样地胸高总断面积的比(RBA)等林分变量时能进一步提高模型预测精度;对于残差方差,指数函数、幂函数和常数加幂函数都能消除异方差,但幂函数效果最好;当模型同时考虑林场效应和林场与样地交互效应时预测精度最高。     

Modeling individual-tree growth in stands under forest conversion in East Germany

One major result of forest conversion in Saxony, East Germany, is the increasing importance of two-storied stands composed of a conifer canopy and a deciduous-tree understory. To enhance the applicability of the growth and yield simulator BWINPro under these conditions, three of its major sub-models were adapted to the regional growing conditions and to the relatively high level of diversity in spatial structure, mixture of species, and age variability typical for forests in conversion: (1) A new module for simulating single-tree juvenile growth was developed for European beech and Common oak under canopies of Norway spruce and Scots pine. Predictions in this sub-model are derived from individual height, diameter at breast height (dbh), and the influences of horizontal and vertical competition; (2) An alternative distance-dependent competition index was introduced to estimate individual basal area increment according to tree-specific growing conditions; (3) A modified logistic mortality model was parameterized for the most important Saxon species based on tree dimensions and basal area increment. Data came from permanent sample plots distributed throughout the region and from three chronosequence plot series established specifically for obtaining model input data. The new components were included into the existing structure of BWINPro. As a result of the adaption, the regional version BWINPro-S provides enhanced opportunities of planning and management for forest conversion and for multi-storied stands.     

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.     

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。     

Predicting Potential Density and Basal Area Development in the Social Forestry Plantations of Acacia nilotica in Gujarat State of India

ABSTRACT

Growth modelling is an important and effective tool for evaluating the effects of a particular management action on the future development of a forest ecosystem. However, such necessary growth models are not available for many indigenous tree species in India. Acacia nilotica is an important multipurpose tree species found in India and growth models are required for proper management of the species in the region. This paper presents equations for estimating potential stand density and predicting basal area in pure even-aged stands of A. nilotica in Gujarat State of India. Although no thinning was suggested, decrease in the number of trees in the stands was observed because of mortality due to overcrowding and some biotic factors. Relationships between quadratic mean diameter and stems per hectare were developed, which was used to establish the limiting density line. Eight different stand level models, belonging to the path invariant algebraic difference form of a non-linear growth function, were compared for projecting basal area. They can be used to predict future basal area as a function of stand variables like dominant height and stem number per hectare and are crucial for evaluating different silvicultural treatment options. The performance of the models was evaluated using different statistical criteria to recommend the suitable model for projecting the basal area in A. nilotica stands.     

Influence of canopy structure on the survival and growth of underplanted seedlings

This study explores the indirect relationship between forest structural measures and initial seedling survival and growth along a structural gradient between 64% to 92% canopy closure. The gradient was created by applying various levels of midstory removal to fifty 0.05 ha areas located within a mixed-hardwood riparian forest corridor. Twelve yellow-poplar (Liriodendron tulipifera L.) and cherrybark oak (Quercus pagoda Raf.) containerized seedling pairs were underplanted within each area. Canopy closure was estimated using hemispherical photography; height-to-canopy and basal area were recorded at each seedling pair. Survival, basal diameter, and height were monitored through two growing seasons. Species-specific mortality and height growth models were developed for one and two growing seasons following underplanting. The interaction of height-to-canopy and basal area along with canopy closure were found to be the most strongly related to mortality. Height to the forest canopy and initial seedling size explained the most variance in height increment. Although the height increment models possess limited predictive power (R² range from 0.22 to 0.36), both mortality and growth analyses emphasize the importance of quantifying vertical canopy structure, along with the more commonly considered horizontal measures of forest structure (basal area and stem density), when evaluating seedling development beneath a forest canopy.     

Growth and yield models for uneven-sized forest stands in Finland

Uneven-sized forestry is gradually gaining popularity and acceptability also in the Nordic countries. This is because of the willingness of the public and some forest owners to avoid clear-fellings and pursue more near-nature forest structures. It has also been realized that the profitability of uneven-sized forestry may be competitive with even-aged forestry. In Finland, management of uneven-sized stands is hampered by the lack of information about the dynamics of such stands, and about the yield and profitability of uneven-sized forestry. This study developed models which allow managers to simulate the growth and yield of uneven-sized stands in Finland, making it possible to predict the yield and analyze the sustainability of different management options. The model set consists of individual-tree diameter increment, height and survival models, and a model for ingrowth. The modeling data consisted of two long-term field experiments of uneven-sized forest management, a set of temporary sample plots measured earlier for growth modeling purposes, and the sample plots of the third National Forest Inventory of Finland. The application area of the models covers all growing sites, all main tree species, and the whole surface area of Finland. According to the models, the sustainable harvest of a fertile (Oxalis-Myrtillus site) uneven-sized Norway spruce forest varies between 5.5 and 7 m³ ha⁻¹ a⁻¹ in Central Finland, depending on the length of the cutting cycle, stand density, and shape of the diameter distribution. It is profitable to harvest large diameter classes more heavily than small ones. Due to the large amount of data the models for diameter increment are highly significant and reliably show the growth level of trees in uneven-sized stands. The weakest models are the ingrowth models, which are based on a clearly smaller data set than the other models.     

系统收获表研究的概念和功能(英文)

传统收获表是指某一树种在特定地区和管理体系下，以立地条件和年龄为变量描述林分平均生长过程的数表．林分密度管理图是根据林分密度效果编制的可预测林分平均收获的图．通过与传统收获表和林分密度管理图的概观比较和探讨，该文系统地阐述了系统收获表的概念和功能．系统收获表的基本特点是为预测现实林分在不同立地条件和管理体系下生长过程的计算机程序．因此，系统收获表能描述在多维变量（如年龄、立地条件、林分密度、胸径和树高）条件下的现实林分和单木的无数生长过程     

A basal area increment model for individual trees in mixed continuous cover forests in Iranian Caspian forests

The aim of this study was to develop and test a new basal area growth model in mixed species continuous cover forests in northern Iran.Weanalyzed 421 core samples from 6 main species in the forest area to develop our growth model.In each plot,we measured variables such as total tree height(m),diameter at breast height(DBH)(cm)and basal area of larger trees as cumulative basal areas of trees(GCUM)ofDBH[5 cm.The empirical data were analyzed using regression analysis.There was a statistically significant nonlinear function between the annual basal area increment,as the dependent variable,and the basal area of the individual trees and competition as explanatory variables.Reference area from the largest trees,was circular plot with area of 0.1 ha.GCUM was estimated for trees of DBH>5 cm.Furthermore,we investigated the dependencies of diameter growth of different species on stand density at different levels of competition,and diameter development of individual trees through time.The results indicate that competition caused by larger neighborhood trees has a negative effect on growth.In addition,the maximum diameter increment is affected by competition level.Therefore,the maximum diameter increment of species occurs when the trees are about 35–40 cm in dense-forest(40 to 0 m^2 per ha)and when the trees are about 60 to 70 cm in very dense forest(60 to 0 m^2 per ha)which is more likely to Caspian natural forests with high level density due to uneven-aged composition of stands.     

A forest biomass yield table based on an empirical model

We report an empirical model for estimating unutilized wood biomass, and its application to Cryptomeria japonica D. Don and Larix kaempferi in Tohno City, Iwate Prefecture, northeast Japan. Outputs from the model are the quantity of unutilized wood biomass and merchantable volume produced by timber harvest. The unutilized wood biomass is divided into stumps, tops, branches, foliages, small trees, and unutilized stems due to their defects. Inputs to the model are mean diameter at breast height (DBH), mean tree height, trees per unit area, and timber utilization standards. DBH distribution, DBH–height curve, stem form, bark thickness, and relationship of stem biomass to foliage and branch biomass could be described by the proposed model, indicating its validity. The proposed model enables us to develop the forest biomass yield tables modified from the existing stem volume yield tables. The developed forest biomass yield tables indicated that the unutilized wood biomass due to defects accounted for the largest part of the whole unutilized wood biomass, and that the ratio of unutilized parts in stem volume to total stem volume could vary with stand age and site productivity class. Based on a comparison of the developed forest biomass yield tables with those reported previously, we concluded that the proposed model-based forest biomass yield table would be useful for estimating the quantity of unutilized wood biomass.     

Basal area growth models for individual trees of Norway spruce, Scots pine, birch and other broadleaves in Norway

Distance-independent individual tree growth models based on about 30,000 observations from the National Forest Inventory and the Norwegian Forest Research Institute have been developed for the main tree species in Norway. The models predict 5-year basal area increment over bark for trees larger than 5 cm at breast height. Potential input variables were of four types: size of the tree, competition indices, site conditions, and stand variables including species, mixtures and layers. The squared correlation coefficient (R²) varied from 0.26 to 0.55. The accuracy of the models was tested by comparing the individual tree models with Norwegian diameter increment models. The accuracy is similar, but individual tree models forecast diameter distributions directly. The inclusion of species mixture and layer as variables increases the reliability of the models in mixed and in uneven-aged stands.     

Growth and yield models for Dahurian larch plantations

IntroductionDahurianlarch(L8risgmeliniiRupr.)isoneofthemostimportanttimberspeciesinChina.AsaresuItofovercuttingforseveraIdecades,thenaturaIDahurianIarchforestresourcesaredecliningrapidly.PIantationsofdahurianIarchhavebecomeanimportantpartofforestpreserveresourcesinDaxing'anMountains.ConsequentIystudyingthegroWthofDahurianlarchandformingtheforesttabfesareofsignrficancetofor-estproduction.ThispaperpresentsinformationongroWthandyieIdmodeIsofDahurianlarchpIantations.MethodsDataof4O5stema…     

Estimation of a basal area growth model for individual trees in uneven-aged Caspian mixed species forests

The aim of this study was to estimate a basal area growth model for individual trees in uneven-aged Caspian forests. A survey was conducted in order to find a natural forest without any harvesting activities, a so called ‘untouched forest’ and an area was selected from the Iranian Caspian forest. Three sample plots in the same aspect and of the same forest type were selected. In each plot, total tree height, diameter at breast height, distance of neighbor trees and azimuth were measured. Thirty trees were selected and drilled with increment borer to determine the increment model. Regression analysis was used to estimate the growth model. Results show that, for individual trees, there is a significant nonlinear relationship between the annual basal area increment, as the dependent variable, and the basal area. The results also show that the basal area of competing trees has a positive influence on growth. That the increment is higher with more competing neighboring trees is possibly because plots with higher volume per hectare and more competition, most likely also have higher site index or better soil or better site productivity than the plot with lower volume per hectare.     

The precision of species proportion by area when estimated by angle counts and yield tables

In Europe yield tables are frequently used to get informationon future total crops as well as on current and future incrementsper hectare and thus the database for forest valuations, decisionson allowable cut and other management decisions. These yieldtables usually claim to describe potential growth and yieldper hectare of even-aged pure species stands. As a prerequisiteto the use of these yield tables in mixed species, even-agedstands, the area to which every species has to be related needsto be known. The way to calculate this area is to split up thearea of the mixed stand into areas each of which is occupiedby a ‘fully stocked’ pure stand of one species.Stocking is measured in terms of observed basal area versusbasal area given by the yield tables. Thus the species proportionby area is calculated from the ratios between the observed andthe respective yield table basal areas. In order to obtain thenecessary sample size for a given precision of the species proportionby area, its variance is calculated from Gauss's law of errorpropagation with the species proportion by basal area and theratio between the respective basal areas as they are given byan appropriate yield table as independent variables. Estimatesof these variables indicate that 3 to 12 angle counts per stand(basal area factor BAF = 4 m² ha^–1) are sufficient fora standard error of ±10 per cent for the species proportionby area, and 9 to 50 angle counts for one of ±5 per cent.     

A normal yield table forLarix gmelinh in Daxin ganling based on the maximum growth rate method

Normal yield tables forLarix gmelimii (Rupr) Rupr. were constructed from 228 temporary sample plots. A normal stand was defined as having the maximum growth rate parameter, based on the theory of forest growth. Basal area growth curves were described with Richard’s equation according to Von-Bertalanffy’s growth theory and allometric law. The growth rate parameter was found to be K, so a normal stand had maximum K. Thus, the basal area growth curve of a normal stand was obtained simply by increasing K. A normal yield table forL. gmelinii of Daxinganling natural forest was then constructed.