Competition effects in an afrotemperate forest

Background： Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods： The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index （CI） and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results： Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions： The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of Cl- growth relations.     

Estimating Pinus palustris tree diameter and stem volume from tree height,crown area and stand-level parameters

Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.     

Over-mature beech trees (Fagus orientalis Lipsky) and close-to-nature forestry in northern Iran

Oriental Beech is the most important commercial tree species in northern Iran. In recent years wood production companies interested in felling large beech trees for profit have challenged advocates of close-to-nature silviculture who favor conservation. Our study objective was to assess the economic value of over-mature beech trees by relating tree diameter (DBH) to amount of decay. Based on the location of onset of decay, we categorized three types of decay as stump, stem, and crown decay. Trees of greater diameter (age) typically showed greater decay in the stem. Percent of decayed volume, diameter of decayed tissue, and length of decay in tree stems varied between 0.5%?64.3%, 15 cm?75 cm, and 2.0?19.5 m, respectively. With increasing trunk diameter, the proportion of truck decay increased. Red heart and dark red heart constituted 25% and 14.3% of sampled trees, respectively. However, we found no correlation between intensity of stem decay and morphological characteristics of trees. Seedlings were not abundant around the bases of over-mature trees, suggesting that the trees did not contribute to regeneration of the stand. Beech trees of diameter >1 m do not provide valuable round wood for industries and cause to raise wood production costs. We recommend that these trees >1 m DBH should be retained in forest stands because of their low commercial value but high ecological and conservational values such as maintaining biodiversity in forest ecosys-tems.     

Determining structural variation in a managed mixed stand in an old-growth forest,northern Iran

Numerous approaches have been developed to quantify forest structure modules.A variety has measured each as part of stand attributes.This study was carried out in managed mixed stands in northern Iran.The objective was to quantify stand structure and its variation before and after tree marking through the Gini index and structural triangle method.A full sampling inventory was taken in 2004 and 2014 at the beginning and end of a period,before and after tree marking operations in five stands.The results indicate that the Gini index was 39.5,62.2,43.0,82.0 and 74.0%forⅠ,Ⅱ,Ⅲ,ⅣandⅤstands respectively.Furthermore,approximate structural diameters were determined as a large category forⅠ,Ⅱ,ⅢandⅤstands while standⅡhad an intermediate-large class pre-tree marking to an intermediate-small class post-tree marking.The paired t-test results were not significant for tree numbers and growing stock changes for all species,and for beech,hornbeam,and velvet maple before and after tree harvesting in the whole stand.Therefore,the Gini index and the structural triangle method can be used for natural stand modeling,structural diversity designation,and for management practices in nature-oriented forestry strategies.     

Larix olgensis growth-climate response between lower and upper elevation limits:an intensive study along the eastern slope of the Changbai Mountains,northeastern China

Larix olgensis is a dominant tree species in the forest ecosystems of the Changbai Mountains of northeast China.To assess the growth response of this species to global climate change,we developed three tree-ring width and biomass chronologies across a range of elevations in the subalpine forests on the eastern slope of the Changbai Mountains.We used dendroclimatic analyses to study key factors limiting radial growth in L.olgensis and its variation with elevation.The statistical characteristics of chronologies suggested that elevation is a determinant of tree growth patterns in the study area.Response function analysis of chronologies with climate factors indicated that climate–growth relationships changed with increasing elevation:tree growth at high elevation was strongly limited by June temperatures of the previous year,and as elevation decreases,the importance of temperature decreased;tree radial growth at mid-elevation was mainly controlled by precipitation towards the end of the growing season of the current year.Biomass chronologies reflected a stronger climatic signal than tree-ring width chronologies.Spatial correlation with gridded climate data revealed that our chronologies contained a strong regional temperature signal for northeast China.Trees growing below timberline appeared to be more sensitive to climate,thus optimal sites for examining growth trends as a function of climate variation are considered to be just below timberline.Our study objective was to provide information for more accurate prediction of the growth response of L.olgensis to future climate change on the eastern slope of the Changbai Mountains,and to provide information for future climate reconstructions using this tree species in humid and semi humid regions.     

Analysis of root fractal characteristics in remote areas of the Taklimakan desert, China

Fractal geometry is a potential new approach to analyze the root architecture, which may offer improved ways to quantify and summarize root system complexity as well as yield ecological and physiological insights into the functional relevance of specific architectural patterns. Fractal analysis is a sensitive measure of root branching intensity and fractal dimension expresses the ＂space filling＂ properties of a structure. The objective of this study was to find out the fractal characteristics of root systems in a remote area of the Taklimakan desert in China. The entire root system of two naturally occurring species were excavated and exposed with shov- els in 2007. The species were Tamarix taklamakanensis and Calligonum roborovskii. A one-factorial ANOVA with species as factor showed statistically a highly significant difference in fractal dimensions, indicating differences in their pattern of root branching. There was no relationship between root diameter and two parameters of fractal root models a and q, representing general characteris- tics of root systems, for either species （a： the ratio of the sum of root cross-sectional areas after a branching to the cross-sectional area before root division; q： the distribution of the cross-sectional areas after branching）. We have found significant linear relation- ships between the diameter after branching and root length and biomass respectively, because of the self-similarity of root branching. Branching rules are the same for roots of all sizes and lengths. Root biomass for the root systems of entire trees can be estimated by measuring the diameter of each root at the base of the trunk or the diameter after branching. We have shown that the diameter of each root at the base of the trunk and the diameter after branching are effective indices that can be measured easily in order to estimate the root lengths, biomass and other parameters of root architecture.     

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.     

Evaluation of early growth performance of 41 clones of teak(Tectona grandis Linn. f.) at four microsites in Purwakarta,Indonesia

Teak(Tectona grandis Linn. f.), one of the mostvalued tree species in the world, is slow-growing with a long period until it can be harvested;therefore, ensuring that only high-quality seedlings or clones are selected for planting is critical. The main objective was to determine performance and repeatability of selected clones in terms of growth and survival rates in different micro-environments. A 2-year clonal trial using 41 clones and a local seedling of teak as a control were grown at 4 microsites differing in spacing, soil fertility and alley crops to assess tree height, diameter and survival rate that was evaluated in Purwakarta, West Java, Indonesia using a randomized complete block design with four replicates of each clone at each microsite. Teak growth was influenced by clone(p < 0.01), microsite(p < 0.05) and clone 9 micrositeinteraction(p<0.01). The interaction clone 9 microsite resulted in several potential superior clones that differed in terms of growth rates at each microsite. On the basis of diameter only, superior clones(nos. 14, 18, 24, 30 and 37)were identified. Repeatability estimated was Rc2= 0.84 for diameter and Rc2= 0.77 for height. Growth performance of teak trees varied among microsites. Repeatability values for diameter and height characters were high. The effect of variable growth on each clone was influenced by genetic factors, environmental factors and the interaction of genetics 9 environment. Microsite significantly affected growth of teak clones. Clone 9 microsite interaction significantly affected growth of clones and led to the growth of superior clones at each microsite.     

杨树新无性系木材性质的变异研究

The wood basic density, cellulose content and fiber form were investigated for all sample trees at breast height (1.3m) in seven poplar clones, and at 0 (butt), 5.6, 9.6, 13.6, 17.6, 19.6 and 21.6 m for clone Nanlin-95 and Nanlin-895, respectively,for providing information on variation patterns of wood density, fiber characteristics and holocellulose content within trees and among clones. The results showed that significant variations about wood density, cellulose content, fiber diameter and the ratio of fiber length to diameter existed among poplar clones examined. Variance analysis indicated that there were significant differences in wood basic density, fiber length, fiber diameter and cellulose content among the growth rings, which had an increasing tendency along the direction from pith to bark. The significant differences also existed in wood basic density, fiber length and fiber diameter at different tree height. The mean wood basic density had a general increase trend with increasing height of trees and the lowest was found at the base, while fiber length and fiber diameter had a general decline pattern with increasing height of trees and the biggest value was observed at the height of 5.6 m. Regression analysis indicated that the relationship between examined wood properties and growth ring number (cambial age), and the relationship between examined wood properties and tree height can be described by polynomial functions.     

Reconstructing the size of individual trees using log data from cut-to-length harvesters in Pinus radiata plantations: a case study in NSW,Australia

With their widespread utilization, cut-to-length harvesters have become a major source of ‘‘big data' for forest management as they constantly capture, and provide a daily flow of, information on log production and assortment over large operational areas. Harvester data afford the calculation of the total log length between the stump and the last cut but not the total height of trees. They also contain the length and end diameters of individual logs but not always the diameter at breast height overbark(DBHOB) of harvested stems largely because of time lapse, operating and processing issues and other system deficiencies. Even when DBHOB is extracted from harvester data, errors and/or bias of the machine measurements due to the variation in the stump height of harvested stems from that specified for the harvester head prior to harvesting and diameter measurement errors may need to be corrected. This study developed(1) a system of equations for estimating DBHOB of trees from diameter overbark(DOB) measured by a harvester head at any height up to 3 m above ground level and(2) an equation to predict the total height of harvested stems in P. radiata plantations from harvester data. To generate the data required for this purpose, cut-to-length simulations of more than 3000 trees with detailed taper measurements were carried out in the computer using the cutting patterns extracted from the harvester data and stump height survey data from clearfall operations. The equation predicted total tree height from DBHOB, total log length and the small end diameter of the top log. Prediction accuracy for total tree height was evaluated both globally over the entire data space and locally within partitioned subspaces through benchmarking statistics. These statistics were better than that of the conventional height-diameter equations for P. radiata found in the literature, even when they incorporated stand age and the average height and diameter of dominant trees in the stand as predictors. So this equation when used with harvester data would outperform the conventional equations in tree height prediction. Tree and stand reconstructions of the harvested forest is the necessary first step to provide the essential link of harvester data to conventional inventory, remote sensing imagery and Li DAR data. The equations developed in this study will provide such a linkage for the most effective combined use of harvester data in predicting the attributes of individual trees, stands and forests, and product recovery for the management and planning of P. radiata plantations in New South Wales, Australia.     

庞泉沟自然保护区优势种种群竞争关系及其动态预测

利用Hegyi单木竞争指数模型对庞泉沟自然保护区优势种群的种内、种间竞争关系进行了定量分析。结果表明:种内和种间竞争强度随着林木径级的增大而逐渐减小,种内竞争较之与其伴生树种间的竞争剧烈。华北落叶松种内、种间竞争强度大小顺序为:种内>云杉>红桦>白桦>关帝柳>花楸>山杨。竞争强度与对象木胸径之间存在显著的幂函数非线性回归关系,回归结果与林分实际相符,从而为庞泉沟自然保护区混交林理论研究和合理经营提供了科学依据。     

樟树福建柏混交林种内及种间竞争研究

通过对樟树福建柏混交林40个样圆的调查,以樟树为对象木,采用Hegyi单木竞争指数模型分析樟树的种内种间竞争关系.结果表明,樟树的种间竞争强度大于种内竞争强度,并且竞争强度随对象木径级的增大逐渐减小.当对象木径级≥23 cm时竞争强度变化较小,径级在14～17时受到的种间竞争强度最大.樟树种内、种间、林分的竞争强度符合幂函数CI =AD-R的关系,用此模型拟合各径级的种内、种间竞争强度效果良好,可对不同径级的樟树所受的竞争强度进行预测.     

濒危植物泰山柳种内与种间的竞争关系

以整合的基径代替胸径,采用Hegyi单木竞争指数模型对灌木泰山柳进行种内与种间的竞争关系分析。结果表明:泰山柳的种内、种间竞争强度分别占总竞争强度(86.11)的35.01%、64.99%,说明泰山柳的竞争压力主要来自种间。随着泰山柳基径的增加,种内、种间竞争强度均逐渐降低。对泰山柳产生竞争影响的树木共9种,其竞争强度为泰山柳>花楸树>紫椴>油松>连翘>湖北海棠>天目琼花>金花忍冬>巧玲花。整个林分和伴生树种竞争指数都与对象木基径近似地服从幂函数关系(I C=AB-K),根据函数模型可以看出,当泰山柳基径达到10 cm后,竞争强度趋于平稳,而基径小于10 cm的泰山柳竞争强度激烈,可以清除其周围部分竞争木,给予足够的生存空间,从而达到保护的目的。     

Quantitative analysis for interspecific relationship of larch stand mixed with ash

Lastvears.manvrescarchaboutintcr-sPecificrclationshipofmixcdstandsforIarchandasht`crcrePeatcd,mostof\`tich,hot`cvcr,isfortheplantingtypeoflinc-bclt.Thispaperanalysisash-larchrclationshipfor26agcdartificialIarchstandmixedwithcvenagcdashinnaturalreqencration.SlTEANDMEASUREMENTMETHOl)ArtincialIarchstandmcasuredlocatcdatecologicaIcxPCrimcntstationinMaocrshanMountainForcstryFarmofNortbcastForcstryUnivcrsity'(El27'34',N45"24').LarchttasplantcdonagrcatPCaccofdescrtcdfieIdinl967t"itha…     

COMPETITION IN OLD GROWTH KOREAN PINE FOREST

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甘肃连城国家级自然保护区青海云杉种内种间竞争的研究

采用Hegyi提出的单木竞争指数模型对甘肃连城国家级自然保护区的青海云杉种内、种间的竞争指数进行定量分析。结果表明:青海云杉种内竞争指数随着林木径级的增大而逐渐减小,种内竞争远远大于种间竞争,种内种间竞争指数的大小顺序为青海云杉>青杄>桦叶四蕊槭>山杨>红桦>柳树;竞争指数与对象木的胸径之间服从幂函数关系CI=AD~B,当青海云杉胸径达到45cm以上时,竞争指数变化很小;青海云杉的竞争指数与海拔和郁闭度呈显著正相关性。     

帽儿山地区山杨次生林林木竞争关系的研究

基于山杨（Poptdus davidianaD．）次生林固定标准地M712、M720的每木检尺数据,采用Hegyi单木竞争指数对帽儿山林场天然山杨次生林的种内、种间竞争强度进行定量分析。研究结果表明：山杨次生林林木所受到的竞争强度随着林木径级的增大而逐渐减小。山杨次生林种内竞争较与伴生树种枫桦的种间竞争弱。山杨次生林种内和种间竞争强度的顺序为：枫桦〉白桦〉蒙古栎〉杏树〉黄菠萝〉山杨〉胡桃楸〉槭树〉榆树〉水曲柳〉椴树〉暴马丁香〉桦树〉花楸〉花曲柳〉色木。     

云南松天然林的种内和种间竞争

[目的]通过对云南松天然林内云南松种内和种间竞争强度的测定,分析揭示竞争强度在云南松群落内的动态变化规律及云南松种群的生态适应机制.[方法]在云龙天池自然保护区云南松天然林设置样方进行群落学调查的基础上,采用Hegyi单木竞争指数模型,以云南松为对象木,定量分析林分、对象木、竞争木的竞争强度,采用回归分析方法建立对象木胸径与林分、种内、种间竞争强度的函数模型.[结果]天池自然保护区云南松天然林的种内和种间竞争强度分别为80.16%和19.84%;云南松种内与主要伴生树种种间竞争强度大小顺序为:云南松种内> 水红木> 华山松> 米饭花> 大白花杜鹃> 槲栎> 马缨花> 旱冬瓜;云南松与整个林分、伴生树种以及种内的竞争强度与对象木胸径之间存在显著负相关关系,对象木胸径越大,其竞争能力越强.[结论]云南松天然林内云南松的竞争压力主要来自种内竞争;林分种内及种间竞争强度与对象木胸径间存在CI=AD^-B形式的幂函数关系;胸径20 cm以上云南松的竞争压力变化趋于平缓,胸径20 cm以下的云南松中、幼林是抚育管理的重点林分.     

基于分层的典型中亚热带天然阔叶林林木竞争关系研究

[目的]通过分析不同林层林木之间的竞争情况,以期揭示林木间相互竞争的类型、林木受到的竞争压力与林木垂直分布之间的关系,为森林资源的保护与利用提供科学依据。[方法]在福建万木林自然保护区内设5块典型中亚热带天然阔叶林样地,采用Hegyi的竞争指数,按分层和不分层两种情形研究林木间的竞争强度。[结果]在1—5号样地,当取样半径超过4 m后,林木间的竞争强度随取样半径的增大而减小的趋势变缓,4 m是分析林木竞争的适宜半径;以4 m为半径分析林木间的竞争,发现有一半以上的组成树种只发生种间竞争,剩余同时发生种间和种内竞争的树种,其竞争木构成中数量占优势的普遍是与其相异的树种,且种间竞争强度普遍强于种内竞争;各样地的乔木层都可以划分出由高到低的3个林层,在平均水平,越高层的林木距离竞争木越远、在竞争木的组成中较矮小的第3林层林木数量也越多;越高层的林木,平均每株对象木与其全部竞争木之间的竞争压力越小。[结论]在调查的典型群落中,普遍发生的是种间竞争,而林木受到的竞争压力及其竞争木的组成都与它们的垂直分布关系密切,在森林资源保护和经营中应对垂直分布予以更多的关注;乔木层中的优势树种未发生激烈种间或种内竞争;可以发生激烈种间竞争的乔木树种有米槠、庆元冬青、少叶黄杞和杜英,不存在特定的竞争木与它们竞争,它们与竞争木相近、主要分布在第2或第3林层;种内竞争过于激烈的有山杜英、华杜英、山黄皮、野含笑和羊舌树,也主要分布在第2或第3林层。     

乳源木莲杉木混交林生长及其竞争关系分析

阔叶林尤其是常绿阔叶林是亚热带地区的地带性植被,它的存在对维护我国广大南方地域的生态平衡、满足经济建设和人民生活需要起着极其重要的作用。但近年来,阔叶林的人为破坏及阔叶树种人工培育不受重视,加上发展针叶人工林,致使针阔比例严重失调,产生一系列生态问题,很多优良乡土阔叶树种随着天然林的肆意砍伐利用而逐步消失(盛炜彤,1993;俞新妥,1997;陈存及等,2000)。为了扭转这种局面,福建省近年来开始重视阔叶树种的造林,大力挖掘优良乡土树种和寻找新树种,特别是珍稀速生阔叶树种。但是很多优良乡土树种连采种育苗都极为困难,乳源木莲…