云南松林可燃物的垂直分布及影响因子

为研究可燃物负荷量空间分布对林火种类和火行为的影响,以川西南地区不同类型云南松林的冠层可燃物和地表可燃物、4个地形因子(海拔、坡度、坡位和坡向)和4个林分因子(郁闭度、胸径、树高和林龄)为对象,比较不同林分相同垂直层面和不同空间层次上的可燃物负荷量及分布特征,分析不同林分的林火行为趋势;并运用典型相关分析(CCA)分析可燃物负荷量与环境因子的关系.结果表明:不同林分组成中,可燃物垂直分布呈显著性差异.云南松-栎类-丁香林、云南松-栎类林和云南松纯林容易发生地表火,但不易发生树冠火;云南松-侧柏林、云南松-油杉林和油杉-云南松林易发生地表火,而且易转化为树冠火.冠层可燃物主要受林龄、海拔、胸径和树高的影响,林下可燃物主要受郁闭度、坡度、树高和林龄的影响.     

黄土高原子午岭大披针苔草能量与养分特征

森林地表死可燃物是引起森林火灾的重要原因,掌握森林地表死可燃物载量的分布,对预防火灾和可燃物管理有重要意义.依据1 h、10 h和100 h分类标准,对呼中林区的不同林型内的地表死可燃物载量进行了对比分析.结果表明:樟子松林内死可燃物总载量最高,偃松林内的最低;对不同类型兴安落叶松林群落的地表死可燃物进行比较,发现笃斯越桔-兴安落叶松林内死可燃物总载量最高,而泥炭藓-杜香-兴安落叶松林的最低;此外,相关分析表明,兴安落叶松死可燃物总载量与平均胸径、平均树高、草本盖度、凋落物厚度呈显著的正相关,与坡向、腐殖质厚度等因子呈显著负相关;多元线性回归分析表明,用兴安落叶松林的凋落物厚度、草本盖度、平均树高因子可较好地估算地表死可燃物总载量,进而为森林可燃物的管理和指导森林防火提供科学的依据.     

大兴安岭南瓮河落叶松-白桦混交林地表可燃物含水率

以大兴安岭南瓮河国家级自然保护区落叶松-白桦混交林的阳坡和阴坡2种林分为研究对象,监测2种林分在不同防火期的地表可燃物含水率的动态变化,采用基于平衡含水率和时滞的直接估计法,分析防火期和坡向对地表可燃物含水率预测模型精度的影响。结果显示:不同防火期林内气象因子(防火期影响)及林分郁闭度(坡向影响)不同,地表可燃物含水率变化呈现差异(P0.05),秋季春季,阳坡阴坡。在构建的地表可燃物含水率预测模型中,秋季防火期预测模型精度优于春季防火期预测模型精度,阳坡预测模型精度优于阴坡预测模型精度。因而,在进行森林火险预测预报时,需考虑坡向和防火期对可燃物含水率的影响,分别建立不同的预测模型,将有助于提高火险预测预报精度。     

地形对亚热带山地景观尺度植被格局影响的梯度分析

用 7个指标反映三峡大老岭地区森林群落生境的地形特征 ,采用 DCCA排序方法定量分析不同地形因子对亚热带山地森林植被格局的影响及它们各自的生态意义 ;并分析它们的作用强度沿海拔的变化。结果表明 :1)DCCA排序的前 4个轴分别与海拔、坡位和坡度、坡向和坡面显著相关 ;山地森林植被存在多重尺度和方向的分异格局 ;2 )山地森林群落样方生境的热量、水分 (养分 )和光照条件可主要由海拔、坡位和坡度、坡向等地形特征分别反映 ;3)在垂直梯度上 :海拔的影响在海拔 6 0 0～ 80 0 m和 15 0 0～ 170 0 m最大 ;坡向影响的峰值在山顶带 ;坡度、坡位与坡形的影响在山地中部影响最大 ,其中坡度在海拔 6 0 0 m以下的影响也很显著 ;坡面的影响在山地中部最显著。     

地形与竞争因子对红松胸径与年龄关系的影响

森林年龄结构一直是森林生态学研究的重要内容之一,利用胸径指标间接推测树木年龄是获得森林年龄结构的有效手段。基于黑龙江省小兴安岭林区156株成熟红松解析木数据,分析成熟红松个体胸径与年龄之间关系,探讨地形与竞争因子对红松胸径与年龄关系的影响。研究结果表明:对所搜集的红松解析木数据,海拔、坡度、坡向、竞争因子等因素都对红松胸径与年龄关系产生影响,其中坡向与坡位对红松胸径-年龄关系影响最为明显,而竞争因子的影响较小并且在不同地形条件下表现出差异性。在南坡向-中坡位的红松个体,其胸径与年龄之间表现出了最佳的拟合效果。对地形与竞争因子的影响机理还有待于进一步研究。     

冰雪灾害对森林的影响

冰雪灾害是一种常见的自然灾害,往往对森林造成很大破坏。随着冰在树冠上不断积累,产生的压力逐渐增大,最后超过该部位最大弯曲力矩时林木会受到伤害。受害程度与林分的多种特征,如树种组成和林分密度及林木的多种特征,如胸径、树高、树干尖削度、叶片表面积、树冠对称性、根系、林龄等有密切关系。影响冰雪灾害的外部因素有地形因子和土壤因子,包括海拔、坡度、坡向、坡位和土壤类型、土壤厚度、土壤水分含量。冰雪灾害对林下光照、土壤、凋落物、真菌和森林动物产生影响。冰雪灾害后的林下光照对树种更新、森林动态和恢复具有重要意义。研究冰雪灾害对天然林的影响,长期监测冰雪灾害后的森林动态、林下植物的光环境、森林的养分循环、土壤以及森林动物,特别是土壤微生物的变化,加强森林的防灾管理是今后该领域的研究方向。     

黄泥河自然保护区野猪冬季栖息地利用

2009年11月-2010年1月,根据野猪的生物学特征和黄泥河自然保护区的地形、地貌特点,在研究地区布设47条样线,对保护区的野猪冬季栖息地利用进行了研究,测定了野猪对海拔、坡位、坡向、坡度、植被类型、郁闭度、树高度、树胸径、食物丰富度、隐蔽度、离水源距离和离人为干扰距离等12种生态因子的选择利用情况.结果表明:黄泥河自然保护区野猪冬季多活动在海拔≤1000 m,坡下位的阳坡平坦地带,食物丰富度高,隐蔽度强,郁闭度中等,且离水源≤500 m,离人为干扰>2000 m的阔叶林和针阔混交林内;主成分分析表明,栖息地变量前4个特征值的累积贡献率达到77.5%,较好地反应了野猪的栖息地特征;影响野猪栖息地选择的关键因子是海拔、坡度、离人为干扰距离,次要因子是离水源距离、隐蔽度、树胸径.     

黑龙江省大兴安岭森林生物量空间格局及其影响因素

基于样地实测数据和EVI指数,定量分析了黑龙江省大兴安岭森林生物量空间格局,并利用ArcGIS软件的空间分析与统计工具,分析了气候区、海拔、坡度、坡向和植被类型对森林生物量空间格局的影响.结果表明: 黑龙江省大兴安岭森林生物量为350 Tg,空间上呈聚集分布,生物量有巨大的增长空间.森林生物量密度大小顺序为:寒温带湿润区(64.02 t·hm^-2)＞中温带湿润区(60.26 t·hm^-2);各植被类型生物量密度大小顺序为:针阔混交林(65.13 t·hm^-2)＞云冷杉林(63.92 t·hm^-2)＞偃松 落叶松林(63.79 t·hm^-2)＞樟子松林(61.97 t·hm^-2)＞兴安落叶松林(61.40 t·hm^-2)＞落叶阔叶混交林(58.96 t·hm^-2).随海拔和坡度的增大,森林生物量密度先减小后增加,并且阴坡大于阳坡.大兴安岭森林生物量空间格局随气候区、植被类型和地形因子的梯度变化表现出差异性,在区域尺度上估算生物量密度时,需要充分考虑这种空间差异性.     

北京松山油松林地表可燃物负荷量的影响因素

森林地表可燃物是引起森林火灾的重要因素,研究森林地表可燃物负荷量的影响因子可以为森林可燃物管理提供科学依据。本文对北京松山自然保护区油松林地表可燃物负荷量与地形、林分和地被物因子进行相关性分析和逐步回归分析,通过方差分解计算3类影响因子对可燃物负荷量变化的贡献率。结果表明:(1)地表总可燃物负荷量与草本盖度呈显著负相关。地表活可燃物负荷量与海拔和灌木盖度呈显著正相关,与草本盖度呈显著负相关。地表死可燃物负荷量分别与郁闭度、林分密度和平均树高呈显著正相关,与海拔呈极显著负相关;(2)多元线性回归分析表明,用海拔、郁闭度和灌木盖度3个因子可较好地估算地表活可燃物负荷量;地表死可燃物负荷量可用海拔和郁闭度2个因子进行较好估算。(3)对地表活可燃物负荷量的解释力中,地被物因子林分因子地形因子,地被物因子与地形因子的交互作用贡献率最显著,与林分因子的交互作用贡献率次之。对地表死可燃物负荷量的解释力中,林分因子地形因子地被物因子,林分因子和地形因子的交互贡献率显著,与地被物因子的交互贡献率次之。不同类别地表可燃物的影响因子不同,在进行可燃物管理、森林防火和林分调控的过程中需有针对性。     

河北小五台山天然白桦林草本多样性影响因素研究

主要研究了河北省小五台山地区天然白桦林草本多样性与地形因子及林木生长因子之间的关系。研究结果表明: (1)林木生长因子与坡度呈正相关关系, 其中坡度与冠幅相关性为极显著(p<0.01), 与树高和胸径相关性为显著(p<0.05); 海拔与胸径、冠幅成负相关关系, 且相关性达到显著(p<0.05); (2)郁闭度、树高、胸径、冠幅基本与草本生物多样性呈负相关, 其中郁闭度与草本多样性之间相关性较为明显, 其他生长因子与草本多样性之间相关性均不显著; (3)在海拔1600 m-2000 m 之间,草本多样性随着海拔的升高未呈现出规律性变化, 草本多样性指数均波动范围较小; (4)坡形、坡位等对草本多样性影响较小,而坡度与草本多样性关系较为明显; 各项草本多样性指数变化趋势基本相同, 整体上均随着坡度的增加而呈现递减的趋势。     

大兴安岭呼中林区地表死可燃物载荷量空间格局

利用地统计学方法,依据时滞分类标准对大兴安岭呼中林区地表死可燃物进行了对比研究.结果表明:一级地表死可燃物表现为强烈的空间自相关性,占总地表死可燃物载荷量的55.54%,平均载荷量为762.35gm-2,其载荷量的决定因素是林分因子和立地年龄;二、三级地表死可燃物的平均载荷量之和为610.26g·m-2,具有较弱的空间自相关性,其载荷量的决定因素为干扰历史.地表死可燃物类型和数量影响因素的复杂性和空间异质性是造成插值精度不高的主要原因,但采用实地调查数据,并结合地统计学方法,可快速准确地计算出地表死可燃物载荷量的空间分布格局,可间接为林业管理提供依据.     

Crown allometries are less responsive than stem allometry to tree size and habitat variations in an Indian monsoon forest

While theoretical allometric models postulate universal scaling exponents, empirical relationships between tree dimensions show marked variability that reflects changes in the biomass allocation pattern. As growth of the various tree compartments may be controlled by different functions, it is hypothesized that they may respond differently to factors of variation, resulting in variable tree morphologies and potentially in trade-offs between allometric relationships. We explore the variability of tree stem and crown allometries using a dataset of 1,729 trees located in an undisturbed wet evergreen forest of the Western Ghats, India. We specifically test whether species adult stature, terrain slope, tree size and crown light exposure affect the relationships between stem diameter and stem height (stem allometry), and between stem diameter and crown width, crown area and crown volume (crown allometries). Results show that both stem and crown allometries are subject to variations in relation to both endogenous (tree size, species adult stature) and exogenous (terrain slope, crown light exposure) factors. Stem allometry appears to be more affected by these factors than are crown allometries, including the stem diameter–crown volume relationship, which proved to be particularly stable. Our results support the idea that height is a prevailing adjustment factor for a tree facing variable growth (notably light) conditions, while stem diameter–crown volume allometry responds more to internal metabolic constraints. We ultimately discuss the various sources of variability in the stem and crown allometries of tropical trees that likely play an important role in forest community dynamics.     

大兴安岭呼中地区3种林分的群落特征、物种多样性差异及其耦合关系

准确理解天然林林分群落特征及其与物种多样性耦合关系是提升天然林管理、达到多样性保护的关键。选择大兴安岭呼中地区典型落叶松林、杂木林、白桦落叶松林为研究对象,分别对乔木层、灌木层和草本层特征(高度、胸径、冠幅、盖度等)进行调查并计算丰富度指数、多样性指数和均匀度指数,旨在探究林分间差异及其耦合关系变化。结果表明:(1)乔木层的树高、枝下高表现出杂木林落叶松林白桦落叶松(P0.05);落叶松林的胸径比白桦落叶松林和杂木林的高出6%和11%;灌木层的高度、盖度、地径、冠幅和草本层多度、盖度、高度在森林类型间均未表现出显著差异。(2)3个森林类型的乔、灌、草丰富度指数R、Shannon-Wiener指数及Simpson指数均表现出杂木林最大,乔木层和草本层呈相同规律,即杂木林白桦落叶松林落叶松林,而灌木层表现出杂木林落叶松林白桦落叶松林;白桦落叶松林和杂木林的乔木层均匀度Pielou指数和Alatalo指数约为落叶松林的3倍左右,而在灌木层和草本层在森林类型间差异不显著(P0.05)。(3)典范对应分析(CCA)结果表明林分群落特征和生物多样性关系存在明显森林类型间差异。总体表现为灌木特征(冠幅、地径)、草本层特征(盖度、多度和高度)对多样性均有较大影响;白桦落叶松林和杂木林的胸径对多样性影响明显,而落叶松林的乔木高度(树高、枝下高)对多样性影响较大。杂木林随着灌木盖度、草本高度的增加,草本物种多样性降低、乔木多和灌木物种多样性增加;而落叶松林相同的多样性变化多伴随草本高度增加、多度和盖度变小。灌木层物种多样性增加多与乔木和草本物种多样性降低相伴随,在杂木林中同时伴随着乔木胸径和草本的盖度、多度增大、灌木冠幅变小,而白桦落叶松林则伴随灌木冠幅和草本多度盖度的减小。以上结果表明,林分群落特征与物种多样性存在耦合关系,上述解耦合结果为通过维持良好森林结构、多样性保护具有实践意义。     

Horizontal, but not vertical canopy structure is related to stand functional diversity in a subtropical slope forest

The aim of this study was to analyse the relation of horizontal and vertical canopy structure to tree functional diversity of a highly diverse subtropical broad-leaved slope forest, stratified for different successional stages. This is of particular interest because many key ecosystem processes and functions are related to the arrangement of forest canopies. We assessed the effect of stand-related functional diversity (FD_Q, measured as Rao’s quadratic entropy of leaf traits), together with other environmental variables on horizontal [measured as relative crown projection areas (CPA_r)] and vertical [relative crown overlap, coefficients of variation (CV) of crown positioning variables] structure of the upper canopy at the local neighbourhood level. The analyses with mixed effects models revealed a negative relation (p = 0.025; estimate −0.07) between FD_Q and CPA_r. No significant effect of FD_Q on vertical canopy structure has been found (p > 0.05). The findings are discussed with regard to resource partitioning and niche differentiation of canopy and sub-canopy species. Successional stage positively impacted the CV of crown length (p = 0.019; estimate 0.03) but did not affect other response variables. The sloping terrain strongly influenced vertical canopy structure as revealed by the significant effect of slope inclination on CV of crown length (p = 0.004; estimate −0.05) and of slope aspect on CV of mean crown height (p = 0.036; estimate −0.03). The high complexity of vertical crown positioning depending on the heterogeneous sloping terrain of the study area may have obscured relations of FD_Q to vertical canopy structure.     

Relationship between tree size and insect assemblages associated with Anadenanthera macrocarpa

This study analyzed the effects of tree size, and correlated architectural tree characteristics, on the assemblages of ants and insect herbivores associated with Anadenanthera macrocarpa (Mimosaceae). The latter is a myrmecophilous tree species from the Atlantic rainforest in south-eastern Brazil. Ants and insect herbivores were collected in 30 individuals of A. macrocarpa , ranging from young individuals (>3 m in height) to emergent trees (up to 40 m). Tree height was a strong indicator of other tree characteristics, including trunk diameter, crown height, crown volume, and number of bifurcations. Ants were collected using arboreal pitfall traps and beating, while insect herbivores with beating only. There was a significant increase in both abundance and species richness of ants and insect herbivores with an increase in tree height. In addition, tree height had a significant effect on the species composition of ants and insect herbivores. Assemblages of both taxa showed a nested organization pattern. The species found in small- and medium-sized trees, in general, consisted of a subset of the species found in the crowns and branches of larger, canopy or emergent trees. Thus, in A. macrocarpa , there was not a replacement of insect species with plant ontogeny. This finding is at variance with those conducted in tropical evergreen forests and which show a clear stratification between the understory and canopy insect faunas. Additional studies are needed to explain these contrasting patterns, but it is possible that differences in microclimate are involved. As the forest we studied is semi-deciduous, microclimatic gradients between the understory and the canopy habitat are probably less severe than in an evergreen forest, thus resulting in a lower turnover of species.     

Responses of crown development to canopy openings by saplings of eight tropical submontane forest tree species in Indonesia: a comparison with cool-temperate trees

BACKGROUND AND AIMS: Growth in trunk height in canopy openings is important for saplings. How saplings increase height growth in canopy openings may relate to crown architectural constraints. Responses of crown development to canopy openings in relation to trunk height growth were studied for saplings (0.2-2.5 m tall) of eight tropical submontane forest tree species in Indonesia. The results of this study were also compared with those of temperate trees in northern Japan. METHODS: The crown architecture differed among the eight tropical species, i.e. they had sparsely to highly developed branching structures. Crown allometry was compared among the eight species in each canopy condition (closed canopy or canopy openings), and between closed canopy and canopy openings within a species. A general linear regression model was used to analyse how each species increases height growth rate in canopy openings. Crown allometry and its plasticity were compared between tropical and temperate trees by a nested analysis of covariance. KEY RESULTS: Tropical submontane trees had responses similar to cool-temperate trees, showing an increase in height in canopy openings, i.e. taller saplings of sparsely branched species increase height growth rates by increasing the sapling leaf area. Cool-temperate trees have a wider crown projection area and a smaller leaf area per crown projection area to avoid self-shading within a crown compared with tropical submontane trees. Plasticity of the crown projection area is greater in cool-temperate trees than in tropical submontane trees, probably because of the difference in leaf longevity. CONCLUSIONS: This study concluded that interspecific variation in the responses of crown development to canopy openings in regard to increasing height related to the species' branching structure, and that different life-forms, such as evergreen and deciduous trees, had different crown allometry and plasticity.     

Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees

Background and Aims

Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns.

Methods

Focus is given to relationships between tree height and top-shoot traits, which include the shoot''s leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot''s stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan.

Key Results

Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height.

Conclusions

In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain.     

额尔齐斯河流域垂枝桦林群落结构特征与物种多样性相关分析

为阐明植物群落结构特征和物种多样性之间的相互关系,选择额尔齐斯河流域白桦林国家森林公园的天然垂枝桦(Betula pendula)纯林、垂枝桦苦杨混交林、垂枝桦白柳混交林为研究对象,分林层调查群落的基本特征参数(高度、枝下高、冠幅、胸径、盖度等),计算物种重要值、丰富度指数、多样性指数、均匀度指数,并进行典范对应分析。结果表明:(1)垂枝桦白柳混交林的乔木层树高、枝下高和灌木层的地径、盖度均最高;3种群落的草本层特征参数(除基径)均具有显著差异;垂枝桦白柳林的盖度分别比垂枝桦苦杨林和垂枝桦纯林高19.1%和51.8%。(2)3种群落的乔木层重要值最高为垂枝桦,灌木层为疏花蔷薇(Rosa laxa)、阿尔泰山楂(Crataegus altaica),草本层为莎薹草(Carex bohemica)。(3)3种群落类型中乔木层的丰富度指数R、Simpson指数、Shannon-Wiener指数和灌木层的Pielou指数、Alatalo指数呈现出相同规律,即垂枝桦白柳混交林>垂枝桦苦杨混交林>垂枝桦纯林;草本层中除Alatalo指数之外,其他指数均呈现垂枝桦纯林>垂枝桦苦杨混交林>垂枝桦白柳混交林(P>0.05)。(4)CCA排序结果表明,不同垂枝桦林群落结构特征与物种多样性关系有差异。其中,垂枝桦纯林中,对物种多样性影响最大的是乔木枝下高、灌木株高、冠幅以及草本盖度;垂枝桦苦杨混交林中,对物种多样性影响最大的是乔木高度和冠幅、灌木冠幅和草本高度;垂枝桦白柳林中,对物种多样性影响最大的是乔木胸径、灌木冠幅、盖度以及草本高度。研究表明,乔木枝下高度、灌木冠幅、草本高度是影响3种群落类型物种多样性的主要因素。     

Age‐related Crown Thinning in Tropical Forest Trees

Gap dynamics theory proposes that treefall gaps provide high light levels needed for regeneration in the understory, and by increasing heterogeneity in the light environment allow light‐demanding tree species to persist in the community. Recent studies have demonstrated age‐related declines in leaf area index of individual temperate trees, highlighting a mechanism for gradual changes in the forest canopy that may also be an important, but less obvious, driver of forest dynamics. We assessed the prevalence of age‐related crown thinning among 12 tropical canopy tree species sampled in lowland forests in Panama and Puerto Rico (total N = 881). Canopy gap fraction of individual canopy tree crowns was positively related to stem diameter at 1.3 m (diameter at breast height) in a pooled analysis, with 10 of 12 species showing a positive trend. Considered individually, a positive correlation between stem diameter and canopy gap fraction was statistically significant in 4 of 12 species, all of which were large‐statured canopy to emergent species: Beilschmiedia pendula, Ceiba pentandra, Jacaranda copaia, and Prioria copaifera. Pooled analyses also showed a negative relationship between liana abundance and canopy gap fraction, suggesting that lianas could be partially obscuring age‐related crown thinning. We conclude that age‐related crown thinning occurs in tropical forests, and could thus influence patterns of tree regeneration and tropical forest community dynamics.     

Modeling qualitative and quantitative elements of branch growth in saplings of four evergreen broad-leaved tree species growing in a temperate Japanese forest

Key message

Factors influencing branch growth differed between a qualitative element (whether a branch grows) and a quantitative element (the amount of biomass accretion).

Abstract

We measured branch growth in saplings of four evergreen broad-leaved tree species growing in a temperate Japanese forest. A hierarchical Bayesian approach was used to model two elements of branch growth: a qualitative component [whether branches produce new annual shoots (AS_n)] and a quantitative component (total AS_n mass). The two components were influenced by somewhat different factors. The probability that a branch would produce AS_n was affected by the total mass of previous-year annual shoots (total AS_n–1 mass), branch age, relative branch height, canopy openness measured at the branch tip, maximum canopy openness within a single sapling, and the interaction between canopy openness and maximum canopy openness. The total AS_n mass was influenced by the total AS_n–1 mass, relative branch height, branch inclination, and maximum canopy openness. These two components of branch growth should be considered separately when tree architecture is modeled. In addition, we detected interactive responses among branches within individual saplings. The relative importance of interactive modular response and branch autonomy may differ depending on the status of plants, such as individual age, environmental conditions, and the timing of the measurements. We found considerable similarities in the responses of branch growth to the internal and environmental factors among the species studied. We also found some among-species differences in branch growth responses to the explanatory variables measured.