上海辰山植物园不同生活型木本植物枝叶大小关系的比较

植物枝叶生长普遍存在显著的正相关关系，决定了植物构型塑造和生物量分配。以上海辰山植物园149种木本植物为对象，通过测定顶枝上70 cm长枝条的直径、叶面积及其生物量，比较相同生境条件下不同生活型木本植物的枝叶大小关系。结果表明，枝条截面积与总叶面积间呈异速生长关系（a=1.148 6，CI=1.000 6~1.302 3），枝条干重与叶干重间呈等速生长关系（a=1.054 2，CI=0.921 3~1.205 6），不同生活型均具有相同的斜率系数a。不同生活型的异速生长常量b（y轴截距）存在显著差异，相同枝条截面积下落叶乔木比常绿乔木和常绿灌木具有更大的叶面积，相同枝条干重下常绿乔木和落叶乔木比常绿灌木具有更大的叶干重。这可能与不同生活型木本植物水分竞争效率和叶建成成本差异有关。     

江西常绿阔叶林木本植物不同冠层高度当年生小枝茎构型对叶生物量的影响

以江西阳际峰自然保区69种木本植物为对象,采用标准化主轴回归(SMA)的方法,对不同冠层高度当年生小枝的构件生物量(叶生物量、茎生物量、小枝生物量)与茎构型特征(茎直径、茎长度、茎宽长比、茎体积和茎密度)进行了分析,研究当年生小枝茎构型对叶生物量的影响.结果表明:不同冠层高度及生活型间叶生物量、茎生物量、小枝生物量、茎直径、茎长度、茎宽长比及茎体积均无显著差异,而茎密度差异显著.不同冠层高度及生活型间,叶生物量与茎生物量及总生物量之间均呈显著等速生长关系.小枝叶生物量分别与茎直径、茎体积呈显著异速生长关系,且该异速生长指数在不同冠层高度无显著差异.茎长度、茎宽长比及茎密度对当年生小枝叶生物量变异的解释力较小(<24%).冠层高度和生活型对小枝叶-茎生物量的等速分配关系影响不显著.小枝茎构型中,相比于茎长度、茎宽长比以及茎密度,茎的直径与体积对当年生小枝叶生物量的影响更大,冠层高度对当年生小枝茎构型与叶生物量间的异速分配模式无显著影响.     

热岛效应下亚热带城市植被叶气孔权衡特征及其与叶功能性状的关系

叶片气孔不仅是植物平衡光合-蒸腾关系的重要门户,也是影响大气碳循环与水循环的关键结构。分析热岛效应下福州市乔木、灌木、草本3种生活型和常绿、落叶2种叶习性植物的气孔性状间的差异及其与其他叶功能性状间的权衡关系有助于探究不同类型植物在热环境下的适应策略。以福州市区的自然和半自然植被为研究对象,测定441个植物样本的气孔特征、化学计量特征和形态特征,结果表明：（1）3种生活型、2种叶习性植物的气孔长度（SL）、气孔密度（SD）差异显著（P<0.05）,潜在气孔导度指数（PCI）不存在显著差异（P>0.05）。草本的SL高于灌木和乔木,乔木的SD最高,灌木次之,草本最低;落叶植物的SL高于常绿植物,SD低于常绿植物。（2）SL与SD间的权衡关系稳定存在于3种生活型和2种叶习性植物中,且随着不同生活型和落叶习性植物的生态策略而呈现各异的权衡特征,即当SL一定时,乔木的SD最大,灌木的SD最小,常绿植物的SD大于落叶植物。（3）气孔性状和叶片形态、化学计量特征紧密联系,SL与比叶面积（SLA）正相关（P<0.01）,与叶面积（LA）负相关（P<0.01）;SD与叶氮含量（LNC）、叶磷含量（LPC）、SLA负相关（P<0.01）,与LA正相关（P<0.01）;PCI与LNC、SLA负相关（P<0.01）,与叶厚度（LT）正相关（P<0.05）。（4）复杂的环境是气孔性状变异的重要驱动因素,SL、PCI均与年均温（MAT）负相关（P<0.05）。     

麻栎和闽楠幼苗叶功能性状及生物量对光照和施肥的响应

光照和养分条件是影响植物生长的重要环境因子,不同生活型植物对环境异质性的响应机制不同。以落叶阔叶树种麻栎和常绿阔叶树种闽楠幼苗为研究对象,设置2个光照梯度（全光照和45%全光照）和4个施肥梯度（不施肥、氮磷供应比为5、15和45）共8种处理,研究光照和施肥及其交互作用对麻栎和闽楠生物量和叶形态、生理及化学性状的影响,并探讨了叶功能性状和生物量的关系。结果表明：（1）光照、施肥及其交互作用对光合气体交换参数（除水分利用效率外）、叶绿素荧光参数、叶形态指标（除比叶面积外）、单位质量叶氮含量和根冠比影响显著（P<0.05）。此外,光照和施肥对地上生物量和总生物量影响显著（P<0.05）。（2）全光照显著增加了麻栎和闽楠单株总叶面积和地上、地下生物量及总生物量（P<0.05）,而遮荫降低了非光化学猝灭系数、光合氮利用率和根冠比,增加了单位质量叶氮含量。（3）在全光照处理中,施肥显著增加了麻栎和闽楠水分利用效率（P<0.05）;在遮荫处理中,氮磷供应比45显著增加了麻栎和闽楠净光合速率和水分利用效率（P<0.05）。（4）麻栎和闽楠在全光照中倾向于资源获取策略,在遮荫中偏向于资源保守策略。在光照和施肥处理中,麻栎和闽楠单株总叶面积与地上生物量均显著正相关（P<0.05）。总之,单株总叶面积是预测麻栎和闽楠幼苗地上生物量变化的稳定指标,施肥有助于增加低光环境下麻栎和闽楠幼苗的生态适应能力。     

亚热带59个常绿与落叶树种不同根序细根养分及化学计量特征

不同根序的植物细根具有形态、结构和生理上的差异,基于根序的细根生理生态研究是当前生态学领域研究的重要组成部分。对不同生活型树种不同根序细根的研究可以为森林生态系统的地下细根养分策略提供理论依据。研究结果发现：（1）除了落叶树种P含量和N：P之外,两个生活型树种细根C、N和P含量与化学计量比在不同根序间均具有显著差异（P<0.05）;两者细根C含量、C：N和C：P随根序增加而升高,而N和P含量随根序增加而降低。（2）常绿与落叶树种C、N、P养分含量中C的变异系数最低,且两个生活型树种细根N、P含量的变异系数基本都随根序增加而变大。（3）常绿树种细根的N、P含量均显著低于落叶树种,但C：N和C：P都显著高于落叶树种,C含量和N：P无显著差异。（4）常绿与落叶树种细根养分（碳、氮和磷）异速关系在各个根序之间都存在共同斜率;常绿树种细根N和P含量存在等速生长关系,但落叶树种细根存在P含量增速大于N含量的异速生长关系（指数：α>1）。结论：随根序增加,常绿与落叶树种的细根具有相似的养分变化策略,N、P养分含量在低阶细根中的变异性更小。落叶树种细根生长受到缺P的影响大于常绿树种。落叶树种细根比常绿树种更高的N、P含量和更低C：N和C：P以及常绿与落叶树种细根N、P养分的异速生长关系差异说明落叶树种细根更倾向于采取快速的资源获取策略。     

武夷山常绿阔叶林木本植物小枝生物量分配

小枝是木本植物的重要组成单元,研究其生物量分配策略有利于了解不同物种对环境的响应。本文以武夷山常绿阔叶林群落中19种木本植物的小枝为研究对象,采取标准化主轴回归(standardized major axis,SMA)的方法分析小枝的叶重、叶片面积、叶柄重、茎重、叶数量等性状特征,研究在群落水平上和不同生活型上,常绿阔叶林群落木本植物的小枝生物量分配格局。结果表明:群落水平上小枝重、总叶重和茎重三者间均呈等速生长关系。同样的,在乔木和灌木不同生活型分类中,茎重和总叶重也呈等速生长关系。但是,小枝重和总叶重、茎重之间的关系却不一致:小枝重和总叶重在乔木、灌木中分别呈等速生长关系和异速生长关系;小枝重和茎重在乔木、灌木中分别呈异速生长关系和等速生长关系;此外,单叶重和出叶强度在群落水平上呈负等速生长关系。然而,这种负等速生长关系并不存在于不同生活型的植物中。小枝水平上,总叶柄重和小枝重、总叶重均呈小于1的异速生长关系,即随叶的增大,小枝需要分配更多生物量用于运输组织和支撑结构(叶柄)的构建。因此,叶柄投资是限制亚热带常绿阔叶林当年生枝和叶增大的重要因素,对于小枝和叶大小的优化选择具有重要影响。     

亚热带常绿阔叶林植物叶小枝的异速生长

 植物生态学研究的重要内容之一是识别和定量刻画种间生态变异的主要维数,叶大小小枝大小维（谱）是其中之一,目前的研究相对比较薄弱,两者之间是异速还是等速生长关系仍存在着争论。亚热带常绿阔叶林植物叶大小-枝大小维的研究报道很少。该文以我国东部亚热带典型区域福建梅花山常绿阔叶林的68种常绿乔灌木植物为对象,进行了叶-小枝关系及其生态意义的研究。结果表明：1）小枝茎截面积与叶干重、总叶面积和单叶面积之间的SMA斜率分别为1.29、1.23和1.18,呈现异速生长关系,支持叶大小 小枝大小为异速生长的相关研究结论,但SMA斜率低于预期值,其原因及生态意义有待进一步研究;2）小枝总叶面积与单叶面积呈显著正相关,而与叶片数量不相关,反映了小枝总叶面积的增加主要是由单叶面积大小决定的,可能与这一地区湿润气候有关;而单叶面积与枝条长度呈正相关则可能反映了植物对常绿阔叶林内较弱光照环境的适应;3）叶干重同小枝干重、叶面积为等速生长关系,可能反映了植物与动物之间代谢方式的差异。     

常绿和落叶阔叶木本植物小枝内生物量分配关系研究：异速生长分析

生物量分配是植物净碳获取的重要驱动因素,当年生小枝内部的生物量分配是植物生活史对策研究的一个重要内容。本文采用标准化主轴估计(Standardized major axis estimation,SMA)和系统独立比较分析(Phy1ogenetica11y independent contrast analysis,PIC)的方法,研究了贡嘎山常绿和落叶阔叶木本植物当年生小枝内各组分生物量分配之间的关系。结果显示：小枝干重与茎干重、叶(含叶柄)干重和叶片(不含叶柄)干重,以及茎干重与叶(含叶柄)干重之间均呈极显著的等速生长关系,表明分配到叶或者叶片中的生物量独立于小枝生物量;叶柄干重与叶片(不含叶柄)干重和小枝干重呈极显著的异速生长关系,显示叶柄对小枝内的生物量分配具有重要的影响;在某一给定的小枝干重或叶片干重时,常绿物种比落叶物种具有更大的叶柄干重,即更大的支撑投资。这些结果表明叶柄作为叶片生物量最大化的一个不利因素,影响了小枝内的生物量分配,并且叶片与其支撑结构之间的异速生长关系随叶片生活型的变化而变化。     

长柄双花木叶性状异速生长关系随发育阶段和海拔梯度的变化

长柄双花木(Disanthus cercidifolius var. longipes)是一种仅分布于我国东南地区的珍稀濒危植物。为研究该物种叶性状异速生长关系和叶片资源利用策略及其随发育阶段和海拔梯度的变化规律,该文以分布于江西省不同海拔梯度的长柄双花木群落为研究对象,调查分析了群落中不同发育阶段长柄双花木植株的叶片面积、叶片体积以及叶片含水量与叶片干重之间的异速关系。结果表明:不同发育阶段植株之间叶性状异速生长关系有着显著差异。成树叶片面积的增长速度低于或等于叶片干重的增长速度,幼树、幼苗叶片面积的增长速度低于叶片干重的增长速度; 成树叶片体积与叶片干重呈等速增长,幼树、幼苗叶片体积的增长速度高于叶干重的增长速度; 成树叶片含水量的增长速度低于叶干重的增长速度,幼树、幼苗两性状间保持等速增长。海拔梯度对长柄双花木叶性状异速生长关系也有影响,植株叶体积和叶含水量与叶干重的异速生长指数在不同海拔间有显著性差异。在低海拔区域,叶体积与叶干重呈等速增长,叶含水量的增长速度低于叶片干重的增长速度。在高海拔区域,叶体积的生长速度低于叶干重的生长速度,叶含水量和叶片干重呈等速增长。这说明长柄双花木叶片资源投资策略随着发育阶段和海拔梯度的不同发生变化。成树主要将叶生物量投资于光捕获面积和同化结构,幼树和幼苗则主要投资于维管组织的建设。由于海拔升高会引起风力增大、光强增强和土壤理化性质改变,长柄双花木在中低海拔倾向于增大叶体积以抢占资源,在高海拔倾向于加强机械组织和维管组织的建设来抵抗外界因子干扰。     

我国温带山地森林48种常见树种叶片重量-出叶强度的关系

叶片是植物的主要光合器官, 其质量与数量的权衡关系体现植物对环境的适应策略。在全球气候变化的背景下, 研究叶片质量与数量关系有助于理解植物对环境变化的响应趋势。该研究应用标准化主轴回归方法, 探讨了我国温带山地森林中48个常见树种的单叶干重与出叶强度的权衡关系。结果表明, 所有物种以及落叶阔叶林、常绿和落叶阔叶树种、单叶以及亚冠层阔叶树种的单叶干重与出叶强度表现为异速生长关系; 针叶林、针阔混交林、常绿及落叶针叶树种、复叶以及冠层阔叶树种则表现为等速生长关系。研究结果表明, 叶大小和出叶强度并无恒定的权衡关系。     

Plant diversity patterns in semi-natural grasslands along an elevational gradient in southern Norway

Leaf demography and growth of six common, co-occurring woody plant species that varied in stature (tree vs. shrub) and leaf texture (sclerophyllous, coriaceous, malacophyllous) were examined in a subtropical savanna parkland in southern Texas, USA. We tested the hypotheses that, (a) leaves of plants with evergreen canopies would have longer life spans than those of deciduous species; (b) supplementation of soil moisture would decrease leaf life span in both evergreen and deciduous species; (c) species responses to increased soil moisture availability would be inversely related to leaf longevity; and (d) deciduous growth forms would exhibit a greater growth response to increased soil moisture availability than their evergreen counterparts.A variety of seasonal leaf habits (evergreen, winter-deciduous and summer-deciduous canopies) and leaf life spans (median = 66 to 283 days) were represented by the targeted species, but there was no clear relationship between seasonal leaf habit and leaf longevity. Among species with evergreen canopies, median leaf longevity ranged from short (Zanthoxylum fagara = 116 days; Condalia hookeri = 158 days) to long (Berberis trifoliolata = 283 days) but did not exceed 1 yr. In fact, leaf longevity in evergreen shrubs was often comparable to, or shorter than, that of species with deciduous canopies (Ziziphus obtusifolia = 66 days; Diospyros texana = 119 days; Prosopis glandulosa = 207 days). Augmentation of surface soil moisture had no detectable effect on median leaf life span in any species and there was no clear relationship between leaf longevity and species growth responses to irrigation. Contrary to expectations, species with evergreen canopies responded to irrigation by producing more leaf biomass, longer shoots and more leaf cohorts/year than did deciduous species.Species differences in the annual cycle of leaf initiation, leaf longevity and canopy development, combined with contrasts in root distributions and a highly variable climate, may allow for spatial and temporal partitioning of resources and hence, woody species coexistence and diversity in this system. However, the lack of expected relationships between leaf longevity, leaf habit and plant responses to resource enhancement suggests that structure-function relationships and functional groupings developed in strongly seasonal environments cannot be applied with confidence to these subtropical savannas and thorn woodlands.     

星斗山常绿落叶阔叶混交林木本植物叶功能性状及其多样性特征分析

为探究亚热带常绿落叶阔叶混交林中木本植物叶功能性状的变异特征,以及群落功能多样性在海拔梯度下的响应规律。该研究以鄂西南地区的星斗山国家级自然保护区海拔1 200～1 700 m的常绿落叶阔叶混交林为研究对象,对群落内木本植物的叶面积(LA)、比叶面积(SLA)、叶干物质含量(LDMC)、叶厚度(LT)、叶氮含量(LNC)、叶磷含量(LPC)6种叶功能性状的变异特征进行了分析,并分析了群落水平下木本植物叶功能性状和功能多样性对海拔变化的响应。结果表明:(1)星斗山保护区内木本植物叶面积、比叶面积、叶干物质含量、叶厚度、叶氮含量和叶磷含量平均值分别为151.49 cm~2、247.98 cm~2/g、34.08%、0.21 mm、16.59 mg/g和0.04 mg/g,其变异幅度依次为206.96%、57.00%、28.15%、52.38%、24.83%和76.92%。(2)在植物科、叶习性、生活型和树高4个因素中,科类群对6种叶功能性状的影响最大,其次为叶习性。(3)海拔对叶面积、叶干物质含量、叶磷含量影响极显著(P0.001),但对比叶面积、叶厚度和叶氮含量无显著影响(P0.05)。(4)不同海拔梯度上群落生物承载量、功能丰富度、功能分离度和功能离散度均达到显著差异(P0.05),仅功能均匀度在海拔梯度上差异不显著。     

Leaf functional traits vary with the adult height of plant species in forest communities

Aims Within-community variation accounts for a remarkable proportion of the variation in leaf functional traits. Plant height may be used to explain within-community variances of leaf traits because different microenvironments, especially light intensity, may occur at different heights. This study determines whether or not leaf nitrogen (N) and phosphorus (P) contents as well as leaf mass per area (LMA) are interspecifically correlated with the adult height of forest woody species. We also discuss these relationships with respect to community structure and functions of the ecosystem.Methods A total of 136 dicotyledonous woody species from 6 natural forests (3 evergreen and 3 deciduous ones) in East China (18°44′–45°25′N, 108°50′–128°05′E) were investigated. For each of the 157 species–site combinations, 6 traits were measured: plant adult height relative to the forest canopy (H R), leaf N and P contents per unit area (N area and P area), N and P contents per unit dry mass (N mass and P mass) and LMA. The total variances of each leaf trait across sites were partitioned in a hierarchical manner. The relationships between leaf traits and H R within forest communities were then analyzed using both standardized major axis regression and Felsenstein's phylogenetic independent contrasts. Relationships between evergreen and deciduous forests were compared by linear mixed models.Important findings H R is a robust predictor of leaf N area, P area and LMA, explaining 36.7, 39.4 and 12.0% of their total variations across forests, respectively. Leaf N area, P area and LMA increased with H R in all of the studied forests, with slopes that were steeper in evergreen forests than in deciduous ones. Leaf N mass and P mass showed no significant relationship with H R generally. The increase in leaf N area, P area and LMA with H R across species is assumed to maximize community photosynthesis and may favor species with larger H R .     

Effect of stem length to stem slender ratio of current-year twigs on the leaf display efficiency in evergreen and deciduous broadleaved trees

Aims Branches and leaves are the two main structural units of tree crown composition. Among the adaptive strategies of plants, the functional traits of branches and the relationships between branch traits and leaf traits determine the capacity of trees to access light and space. In this study, our objective is to test the hypothesis that leaf display efficiency is affected by the stem length to stem slender ratio within current-year twigs.Methods The stem length to stem slender ratios of current-year twigs were used as the proxy of stem structure traits. Leaf area ratio (total leaf area per stem mass), leaf density (leaf number per stem length) and leaf/stem mass ratio (total leaf mass per stem mass) were used as the proxies of leaf display efficiency. The relationship between stem structure traits and leaf display efficiency within current-year twigs were studied for 25 evergreen and 60 deciduous broadleaved woody species in Qingliang Mountain, Zhejiang, China. The standardized major axis estimation method was used to examine the scaling relationship between stem structural traits and leaf display efficiency within current-year twigs.Important findings The proxies of leaf display efficiency, measured by leaf area ratio, leaf density or leaf/stem mass ratio, were all significantly and negative correlated with stem length to stem slender ratio within current-year twigs in both evergreen and deciduous broadleaved woody species. This suggested that leaf display efficiency decreased with stem length to stem slender ratios within current-year twigs, which may reflect the role of mechanical safety and light within twigs. The slope of the relationship between leaf display efficiency and stem long-dimension structure traits in evergreen species was not significantly different from the one in deciduous species. In contrast, the y-intercept of the relationship between leaf density and stem long-dimension structure traits was significantly larger in evergreen species than in deciduous species, i.e. the leafing intensity of evergreen species was higher than that of deciduous species. Individual leaf area and specific leaf area were smaller in evergreen species than in deciduous species, which resulted in deciduous species have a larger leaf area per stem mass and leaf mass per stem mass at a given stem length to stem slender ratio compared to evergreen species. It may reflect the conservative adaptive strategy of high consumption and slow benefit in evergreen species. Our results demonstrated that leaf display efficiency could be affected by stem length, and would change with leaf life-span (deciduous versus evergreen).     

Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest

Canopy structure and light interception were measured in an 18-m tall, closed canopy deciduous forest of sugar maple (Acer saccharum) in southwestern Wisconsin, USA, and related to leaf structural characteristics, N content, and leaf photosynthetic capacity. Light attenuation in the forest occurred primarily in the upper and middle portions of the canopy. Forest stand leaf area index (LAI) and its distribution with respect to canopy height were estimated from canopy transmittance values independently verified with a combined leaf litterfall and point-intersect method. Leaf mass, N and A _max per unit area (LMA, N/area and A _max/area, respectively) all decreased continuously by over two-fold from the upper to lower canopy, and these traits were strongly correlated with cumulative leaf area above the leaf position in the canopy. In contrast, neither N concentration nor A _max per unit mass varied significantly in relation to the vertical canopy gradient. Since leaf N concentration showed no consistent pattern with respect to canopy position, the observed vertical pattern in N/area is a direct consequence of vertical variation of LMA. N/area and LMA were strongly correlated with A _max/area among different canopy positions (r²=0.81 and r²=0.66, respectively), indicating that vertical variation in area-based photosynthetic capacity can also be attributed to variation in LMA. A model of whole-canopy photosynthesis was used to show that observed or hypothetical canopy mass distributions toward higher LMA (and hence higher N/area) in the upper portions of the canopy tended to increase integrated daily canopy photosynthesis over other LMA distribution patterns. Empirical relationships between leaf and canopy-level characteristics may help resolve problems associated with scaling gas exchange measurements made at the leaf level to the individual tree crown and forest canopy-level.     

Spatial patterns of photosynthetic characteristics and leaf physical traits of plants in the Loess Plateau of China

The spatial patterns of photosynthetic characteristics and leaf physical traits of 171 plants belonging to nine life-forms or functional groups (trees, shrubs, herbs, evergreen trees, deciduous trees, C₃ and C₄ herbaceous plants, leguminous and non-leguminous species) and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, ranging from south to north in the Loess Plateau of China were studied. The results showed that the leaf light-saturated photosynthetic rate (P_max), photosynthetic nitrogen use efficiency (PNUE), chlorophyll content (Chl), and leaf mass per area (LMA) of all the plants in the Loess Plateau varied significantly among three life-form groups, i.e., trees, shrubs and herbs, and two groups, i.e., evergreen trees and deciduous trees, but leaf nitrogen content differed little among different life-form groups. For the 171 plants in the Loess Plateau, leaf P_max was positively correlated with PNUE. The leaf nitrogen content per unit area (N_area) was positively correlated but Chl was negatively correlated with the LMA. When controlling the LMA, the N_area was positively correlated with the Chl (partial r = 0.20, P < 0.05). With regard to relationships between photosynthetic characteristics and leaf physical traits, the P_max was positively correlated with N _area, while the PNUE was positively correlated with the Chl and negatively correlated with the N_area and LMA. For all the species in the Loess Plateau, the PNUE was negatively correlated with the latitude and annual solar radiation (ASR), but positively correlated with the mean annual rainfall (MAR) and mean annual temperature (MAT). With regard to the leaf physical traits, the leaf Chl was negatively correlated with the latitude and ASR, but positively correlated with the MAR and MAT. However, the N_area and LMA were positively correlated with the latitude and ASR, but negatively correlated with the MAR and MAT. In general, leaf N_area and LMA increased, while PNUE and Chl decreased with increases in the latitude and ASR and decreases in MAR and MAT. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.     

Periodicity of leaf growth and leaf dry mass changes in the evergreen and deciduous species of Southern Assam,India

The study described patterns of leaf dry mass change, leaf mass per area (LMA), relative growth rate and leaf life span (LL) for 14 evergreen and 7 deciduous species of a tropical forest of Southern Assam, India. Leaf expansion in both the groups was, in general, completed before June (i.e. well before the onset of monsoon rains). Although leaf dry mass during leaf initiation phase was significantly higher (P < 0.01) in evergreen species than in deciduous species, at the time of full leaf expansion, average leaf dry mass relative to the peak leaf dry mass, realised by the evergreen species was lower (66 %) than for deciduous species (76 %). Leaf dry mass increase in both groups continued after leaf full expansion. Evergreen species had a longer leaf dry mass steady phase than deciduous species (2–6 vs 2–3 months). Average LMA of mature leaves for evergreen species (77.43 g m^?2) was significantly greater than that of deciduous species (48.43 g m^?2). LL ranged from 165 days in Gmelina arborea (deciduous) to 509 days in Dipterocarpus turbinatus (evergreen). LMA was correlated positively with LL, indicating that evergreen species with higher leaf construction cost retain leaves for longer period to pay back. The average leaf dry mass loss before leaf shedding was greater (P < 0.01) for deciduous species (30.29 %) than for evergreen species (18.31 %). Although the cost of leaf construction in deciduous species was lower than for evergreen species, they replace leaves at a faster rate. Deciduous species perhaps compensate the cost involved in faster leaf replacement through higher reabsorption of dry mass during senescence, which they remobilise to initiate growth in the following spring when soil resources remain limiting.     

浙江天童木本植物小枝的“大小-数量”权衡

枝条大小和数量关系反映了植物适应环境胁迫的构型和生物量分配策略。该研究以浙江天童木本植物为对象, 通过对小枝大小(横截面积)与数量(稠密度)关系的研究发现: 1)小枝稠密度与枝截面积显著负相关(斜率为-1.32, CI = -1.48- -1.17; p < 0.05); 2)在相同曝光度, 在II级曝光环境(植株40%-80%暴露在直射光中)中常绿植物比落叶植物单位小枝截面积的小枝稠密度高, 而在I级(植株<40%暴露在直射光中)和III级(>80%暴露在直射光中)曝光环境中, 小枝稠密度在两种生活型间无显著差异; 3)在不同曝光度下, 常绿植物单位枝条在I和II级比III级曝光水平具有更高的小枝稠密度; 但落叶植物单位枝条的小枝稠密度在3个曝光水平相同; 4)相同枝条大小下, 4 m以下灌木比4 m以上的亚乔木和乔木具有更高的小枝稠密度。总之, 天童地区木本植物的小枝“大小-数量”关系符合Corner法则(描述枝叶“大小-数量”关系的法则), 且在不同生活型间存在差异, 常绿植物相对于落叶植物, 灌木相对于乔木具有较高的小枝稠密度, 从而有利于它们适应光资源的限制。