Within-twig biomass allocation in subtropical evergreen broad-leaved species along an altitudinal gradient: allometric scaling analysis

We studied the effects of twig size and altitude on biomass allocation within plant twigs (terminal branches of current-year shoots), to determine whether species with large twigs/leaves or living at low altitude allocate a higher proportion of biomass to laminas than their counterparts with small twigs/leaves or living at high altitude. Stem mass, lamina mass and area, and petiole mass were measured for terminal branches of current-year shoots in 80 subtropical evergreen broad-leaved species belonging to 38 genera from 24 families along an altitudinal gradient of Mt. Emei, Southwest China. The scaling relationships between the biomass allocations of within-twig components were determined using model type II regression method. Isometric relationships were found between leaf mass and twig mass and between lamina mass and twig mass, suggesting that the biomass allocation to either leaves or laminas was independent of twig mass. Petiole mass disproportionally increased with both lamina mass and twig mass, indicating the importance of leaf petioles to the within-twig biomass allocation. These cross-species correlations were consistent with those among evolutionary divergences. In addition, species at low altitude tended to have a greater leaf and lamina mass but a smaller stem mass at a given twig mass than at middle and high altitudes. This is possibly due to the high requirement in physical support and the low efficiency of eco-physiological transport for the species living at high altitude. In general, within-twig biomass allocation pattern was not significantly affected by twig size but was greatly modulated by altitude.     

清凉峰不同海拔木本植物小枝内叶大小-数量权衡关系

权衡关系是生活史对策理论的基础, 叶大小-数量的权衡关系对理解叶大小进化具有重要的意义。该研究以单叶面积和单叶片干重表示叶大小, 用小枝干重和小枝茎干重表示小枝大小, 采用标准化主轴估计(standardized major axis estimation, SMA)和系统独立比较分析(phylogenetically independent contrast analysis, PIC)的方法, 对浙江省清凉峰自然保护区3个不同海拔落叶阔叶木本植物当年生小枝内的叶大小与数量间的关系进行研究。结果显示, 无论叶大小和小枝大小是用面积或干重表示, 在每个海拔, 叶大小与出叶强度均存在显著的等速负相关关系, 表明在落叶阔叶木本植物中发现的叶大小与出叶强度之间的权衡关系在不同生境物种中是普遍存在的, 植物在叶大小方面的种间变化, 可能不是自然选择的直接产物, 而是叶片数量变化权衡关系的一个副产物。不同海拔间的比较显示, 高海拔物种的叶面积或干重与出叶强度相关关系的y轴截距比中、低海拔物种小, 表明在出叶强度一定的情况下, 高海拔物种比低海拔物种具有更小的叶大小。与高海拔物种相比, 中海拔物种的共同斜率沿共同主轴有一个向上的位移, 表明中海拔物种比高海拔物种具有更大的叶大小, 但出叶强度更小。这些结果表明生境对叶大小-数量的权衡关系具有显著的影响, 中海拔生境具有更适宜植物生长的气候及养分条件, 而高海拔的低温等不利影响使得叶片变小。     

胡杨叶片大小与叶数量的权衡关系对地下水埋深的响应

本文以胡杨(Populus euphratica Oliv.)为研究对象,采用标准化主轴回归估计(SMA)方法探讨了种群叶片大小(单叶面积、单叶质量)与出叶强度(基于小枝质量、茎质量、茎体积)的异速生长关系对地下水埋深梯度(Groundwater depth,GWD)的响应及其变化规律.结果显示:随GWD增加,胡杨当年...     

EFFECTS OF TWIG SIZE ON BIOMASS ALLOCATION WITHIN TWIGS AND ON LAMINA AREA SUPPORTING EFFICIENCY IN RHODODENDRON: AL. LOMETRIC SCALING ANALYSES

 当年生小枝是多年生植物体上最活跃的部分之一, 其生物量分配是植物生活史对策研究的一个重要内容。该文采用标准化主轴估计(Standardized major axis estimation, SMA)和系统独立比较分析(Phylogenetically independent contrast analysis, PIC)的方法, 研究了杜鹃花属(Rhododendron)植物一年生小枝的大小对小枝叶片、叶柄和茎的生物量分配的影响, 以及对叶面积支持效率(即单位质量小枝支持的叶面积)的影响。结果显示: 1)小枝大小对叶片生物量分配比率的影响不显著, SMA斜率为1.040 (95%的置信区间(CI)=0.998～1.085); 但是, 小枝越大, 叶柄生物量分配比例越高(SMA斜率为1.245, 显著大于1.0, 呈显著的异速生长关系)。2)小枝越小, 单叶面积越小(支持Corner法则), 单位质量小枝所支持的叶面积越大, 即具有较小枝条和较小叶片的物种可能具有较高的叶面积支持效率。这些结果有助于我们更好地理解亲缘关系十分接近的杜鹃花属植物, 在不同生境条件下叶片大小的差异, 以及为什么在胁迫生境条件下小叶物种更为常见。     

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。     

The leaf size-twig size spectrum of temperate woody species along an altitudinal gradient: an invariant allometric scaling relationship

BACKGROUND AND AIMS: The leaf size-twig size spectrum is one of the leading dimensions of plant ecological variation, and now it is under development. The purpose of this study was to test whether the relationship between leaf size and twig size is isometric or allometric, and to examine the relationship between plant allometric growth and life history strategies in the spectrum. METHODS: Leaf and stem characters-including leaf and stem mass, total leaf area, individual leaf area, stem cross-sectional area, leaf number and stem length-at the twig level for 59 woody species were investigated along an altitudinal gradient on Changbaishan Mountain in the temperate zone of China. The environmental gradient ranges from temperate broad-leaved mixed forest at low altitude, to conifer forest at middle altitude, and to sub-alpine birch forest at high altitude. The scaling relationships between stem cross-sectional area and stem mass, stem mass and leaf mass, and leaf mass and leaf area at the twig level were simultaneously determined. KEY RESULTS: Twig cross-sectional area was found to have invariant allometric scaling relationships with the stem mass, leaf mass, total leaf area and individual leaf area, all with common slopes being significantly larger than 1, for three altitudinal-zoned vegetation types under investigation. However, leaf mass was found to be isometrically related to stem mass and leaf area along the environmental gradient. Based on the predictions of previous models, the exponent value of the relationship between twig cross-sectional area and total leaf area can be inferred to be 1.5, which falls between the confidence intervals of the relationship at each altitude, and between the confidence intervals of the common slope value (1.17-1.56) of this study. This invariant scaling relationship is assumed to result from the fractural network and/or developmental constraints of plants. The allometric constants (y-intercepts) of the relationships between the stem cross-sectional area and leaf area (both total leaf area and individual leaf area) were found to decrease significantly along the altitudinal gradient. This suggests that the species would support less leaf area at a given twig cross-sectional area with increasing environmental stress. CONCLUSIONS: This study demonstrated that plants respond to the environmental gradient by changing the y-intercepts of the relationship between leaf size-twig size, while keeping the exponent value of the allometric relationship as an invariant constant. The allometric growth in the twig size-leaf size spectrum is related to many other components of plant life history strategy, including the well established life history trade-off between efficiency and safety in the hydraulic transport of water.     

不同海拔典型竹种枝叶大小异速生长关系

为了分析竹子枝-叶大小间的权衡关系,本研究对武夷山不同海拔典型竹种(毛竹、箬竹、肿节少穗竹、毛竿玉山竹和武夷山玉山竹)小枝的叶片总质量、茎质量、单叶质量和出叶强度等性状进行测定.结果表明: 随海拔升高,5个竹种间小枝上总叶质量与茎质量的异速生长指数呈显著下降趋势.竹种内,毛竹、箬竹和肿节少穗竹总叶质量与茎质量在不同海拔上均拥有共同异速生长指数(分别为0.94、0.85、0.84).毛竿玉山竹和武夷山玉山竹的叶茎质量也存在共同异速生长指数(0.79).除武夷山玉山竹外,竹子单叶质量与出叶强度之间均呈显著的负相关关系.5个竹种的单叶质量和出叶强度之间存在共同异速生长指数-1.12.总之,竹类植物的小枝总体上倾向于在低海拔环境中着生更多的叶片,而在高海拔生境下则投资更多的生物量到茎的构造上.尽管竹种间小枝的茎投资随海拔升高而增加,但其基于茎质量的出叶强度策略取决于叶片大小的构建而不是海拔生境差异.     

Size-dependent leaf area ratio in plant twigs: implication for leaf size optimization

Background and Aims

Although many hypotheses have been proposed to explain variation in leaf size, the mechanism underlying the variation remains not fully understood. To help understand leaf size variation, the cost/benefit of twig size was analysed, since, according to Corner''s rule, twig size is positively correlated with the size of appendages the twig bears.

Methods

An extensive survey of twig functional traits, including twig (current-year shoots including one stem and few leaves) and leaf size (individual leaf area and mass), was conducted for 234 species from four broadleaved forests. The scaling relationship between twig mass and leaf area was determined using standardized major axis regression and phylogenetic independent comparative analyses.

Key Results

Leaf area was found to scale positively and allometrically with both stem and twig mass (stem mass plus leaf mass) with slopes significantly smaller than 1·0, independent of life form and habitat type. Thus, the leaf area ratio (the ratio of total leaf area to stem or twig mass) decreases with increasing twig size. Moreover, the leaf area ratio correlated negatively with individual leaf mass. The results of phylogenetic independent comparativeanalyses were consistent with the correlations. Based on the above results, a simple model for twig size optimization was constructed, from which it is postulated that large leaf size–twig size may be favoured when leaf photosynthetic capacity is high and/or when leaf life span and/or stem longevity are long. The model''s predictions are consistent with leaf size variation among habitats, in which leaf size tends to be small in poor habitats with a low primary productivity. The model also explains large variations in leaf size within habitats for which leaf longevity and stem longevity serve as important determinants.

Conclusions

The diminishing returns in the scaling of total leaf area with twig size can be explained in terms of a very simple model on twig size optimization.Key words: Allometry, leaf size, twig size, leaf area ratio, scaling relationship, broadleaved species     

胡杨当年生小枝茎构型对展叶效率的影响

枝叶异速生长关系对理解荒漠植物生物量分配和生活史策略具有重要意义。该研究以小枝茎长度、茎纤细率和茎体积表征茎构型, 以叶密度(单位茎长度的叶数量)、叶面积比(单位小枝茎干质量的总叶面积)和叶茎质量比(单位小枝茎干质量的总叶干质量)表征展叶效率, 采用标准化主轴回归(SMA)方法研究胡杨(Populus euphratica)当年生小枝茎构型对展叶效率的影响及二者沿地下水埋深(GWD)梯度的权衡策略。结果显示, 胡杨当年生小枝茎直径、展叶效率和比叶面积、叶大小随GWD增加而降低, 小枝茎长度、茎纤细率及其上的叶数量则增大。小枝茎构型性状均与展叶效率呈显著负相关关系, 即随小枝茎长度、茎纤细率和茎体积的增加, 展叶效率逐渐降低, 这可能是枝叶大小、水分传导与机械支撑间的权衡结果。小枝茎构型与展叶效率的异速生长指数(斜率)随GWD增加而增大, 是由于单位小枝茎投资获得的叶面积或者叶质量降低所致, 反映出随GWD增加胡杨采取了高消耗低收益的保守型策略。胡杨应对环境压力时, 倾向于在长枝上着生数量较多的小叶, 短枝上着生数量较少的大叶, 体现出胡杨小枝的资源利用策略与枝叶大小的权衡机制。综上所述, GWD显著影响胡杨小枝茎构型-展叶效率的权衡关系, 低展叶效率是胡杨应对日益旱化荒漠环境的适应策略。     

Application of leaf size and leafing intensity scaling across subtropical trees

Understanding the scaling between leaf size and leafing intensity (leaf number per stem size) is crucial for comprehending theories about the leaf costs and benefits in the leaf size–twig size spectrum. However, the scaling scope of leaf size versus leafing intensity changes along the twig leaf size variation in different leaf habit species remains elusive. Here, we hypothesize that the numerical value of scaling exponent for leaf mass versus leafing intensity in twig is governed by the minimum leaf mass versus maximum leaf mass (M _min versus M _max) and constrained to be ≤−1.0. We tested this hypothesis by analyzing the twigs of 123 species datasets compiled in the subtropical mountain forest. The standardized major axis regression (SMA) analyses showed the M _min scaled as the 1.19 power of M _max and the ‐α (−1.19) were not statistically different from the exponents of M _min versus leafing intensity in whole data. Across leaf habit groups, the M _max scaled negatively and isometrically with respect to leafing intensity. The pooled data''s scaling exponents ranged from −1.14 to −0.96 for M _min and M _max versus the leafing intensity based on stem volume (LIV). In the case of M _min and M _max versus the leafing intensity based on stem mass (LIM), the scaling exponents ranged from −1.24 to −1.04. Our hypothesis successfully predicts that the scaling relationship between leaf mass and leafing intensity is constrained to be ≤−1.0. More importantly, the lower limit to scaling of leaf mass and leafing intensity may be closely correlated with M _min versus M _max. Besides, constrained by the maximum leaf mass expansion, the broad scope range between leaf size and number may be insensitive to leaf habit groups in subtropical mountain forest.     

亚热带常绿阔叶林木本植物幼树阶段抽枝展叶的权衡关系

亚热带常绿阔叶林植物幼树阶段适应林内生境并开枝散叶是其长成大树的一个重要过程, 植物一年内多次抽枝的现象及其在抽枝展叶过程中小枝伸长、枝茎增粗与叶面积的增加优先顺序及其内在驱动机制还有待进一步研究。该研究对青城山常绿阔叶林木本植物多次抽枝发生比例进行了调查, 并以茶(Camellia sinensis)、细枝柃(Eurya loquaiana)、短刺米槠(Castanopsis carlesii var. spinulosa)、润楠(Machilus nanmu)和大叶山矾(Symplocos grandis) 5种植物的幼树为研究对象, 比较分析了植物在多次抽枝中小枝和叶片生长动态及适应策略的差异。结果显示: 1)一、二次抽枝分别开始于春季(4月)和夏末(8月下旬), 小枝水平上二次抽枝率乔木小于灌木, 常绿植物小于落叶植物。2)一次抽枝小枝枝长、单叶面积, 小枝直径和叶片数量(除大叶山矾外)均高于二次抽枝, 但二次抽枝单叶面积相对生长速率均高于一次抽枝, 二次抽枝叶片比叶质量(LMA)的增长速率高于一次抽枝。3)一次抽枝小枝枝长、叶片数量、小枝直径(除细枝柃和短刺米槠外)和总叶面积(除短刺米槠外)最大相对生长速率均高于二次抽枝, 且大部分物种最大相对生长速率出现在抽枝开始的第一、二周。4)两次抽枝中, 物种先侧重于叶片的生长, 其次是小枝枝长的生长, 最后是小枝直径的增粗。单叶面积和总叶面积皆随着小枝枝长和小枝直径的增加呈显著的异速生长关系, 表明叶片的增长速度大于小枝。单叶面积与叶片数呈显著大于1的异速生长关系, 暗示单叶面积的增长速度大于叶片数的增加速度。小枝枝长与小枝直径也呈显著大于1的异速生长关系, 揭示小枝枝长的增长速度大于小枝直径。综上所述, 两次抽枝过程中, 植物枝叶的优先生长顺序反映了植物为获取更多的资源(尤其是光源)而形成特定的抽枝展叶策略; 二次抽枝单叶面积相对生长速率和LMA增长速率高于一次抽枝, 这可能与植物即将面临的昆虫取食和气温降低压力有关。因此, 了解植物抽枝策略对于理解物种生态适应机制, 揭示物种生活史过程中存在的权衡关系具有重要的理论意义。     

The generality of leaf size versus number trade-off in temperate woody species

Background and Aims

Trade-offs are fundamental to life-history theory, and the leaf size vs. number trade-off has recently been suggested to be of importance to our understanding leaf size evolution. The purpose of the present study was to test whether the isometric, negative relationship between leaf size and number found by Kleiman and Aarssen is conserved between plant functional types and between habitats.

Methods

Leaf mass, area and number, and stem mass and volume of current-year shoots were measured for 107 temperate broadleaved woody species at two altitudes on Gongga Mountain, south-west China. The scaling relationships of leaf size (leaf area and mass) vs. (mass- and volume-based) leafing intensity were analysed in relation to leaf habit, leaf form and habitat type. Trait relationships were determined with both a standardized major axis method and a phylogenetically independent comparative method.

Key Results

Significant negative, isometric scaling relationships between leaf size and leafing intensity were found to be consistently conserved across species independent of leaf habit, leaf form and habitat type. In particular, about 99 % of the variation in leaf mass across species could be accounted for by proportional variation in mass-based leafing intensity. The negative correlations between leaf size and leafing intensity were also observed across correlated evolutionary divergences. However, evergreen species had a lower y-intercept in the scaling relationships of leaf area vs. leafing intensity than deciduous species. This indicated that leaf area was smaller in the evergreen species at a given leafing intensity than in the deciduous species. The compound-leaved deciduous species were observed usually to have significant upper shifts along the common slopes relative to the simple-leaved species, which suggested that the compound-leaved species were larger in leaf size but smaller in leafing intensity than their simple counterparts. No significant difference was found in the scaling relationships between altitudes.

Conclusions

The negative, isometric scaling relationship between leaf size and number is largely conserved in plants, while the leaf size vs. number trade-off can be mediated by leaf properties. The isometry of the leaf size vs. number relationship may simply result from a biomass allocation trade-off, although a twig size constraint may provide an alternative mechanism.Key words: Allometry, trade-off, leafing intensity, leaf size, leaf habit, leaf form     

Testing of Corner’s rules across woody plants in Tiantong region,Zhejiang Province: effects of individual density

Aims Corner’s rules reflect the architectural strategies of plants with respect to deployment of twig size and leaf size, as well as of the number of twigs and leaves. The objective of this study was to examine how Corner’s rules would vary among plants with different individual densities.
Methods The study site is located in the Tiantong National Forest Park (29.87° N, 121.65° E), Zhejiang Province. We measured twig cross-sectional area (twig size), total leaf area (leaf size per twig), and the number of twigs at a given twig size (branching intensity) in woody plants across 25 plots differing in stem density to examine the effects of individual competition on Corner’s rules. The standardized major axis (SMA) analysis was conducted to determine the quantitative relationships of twig size with leaf size and branching intensity.
Important findings Significant, positive allometric relationships between cross-sectional area and total leaf area were found in individual plants across all communities. There was no significant difference among communities of different density intervals in the slope of the linear regression between cross-sectional area and total leaf area of individual plants, and the common slope of the regressions was significantly greater than 1 (p < 0.001). The intercept was significantly greater for plants in communities with higher density than in those with lower density (p < 0.001), indicating that plants in a high density community support greater total leaf area than in a low density community for a given twig size. In contrast, a significant, negative allometric scaling relationship was found between branching intensity and cross-sectional area in individual plants across different communities. Also, nosignificant difference was found among plants in communities of different density intervals in the slope of the regression between branching intensity and cross-sectional area, and the common slope of the regressions was significantly less than –1 (p < 0.001). The intercept for the regression relationship between twig area and branching intensity was the same among plants in communities of different density intervals (p > 0.05), suggesting that plants in a high density community do not deploy more twigs per twig size than in a low density community. In summary, this study demonstrated that plants responded to changes in individual density by maintaining an invariant regression slope for the twig size-leaf size relationship and the twig size-branching intensity relationship, and that the Corner’s rules were not affected by individual density of the communities in the Tiantong region. However, changes in the intercept of the regression between twig size and leaf size indicate that deployment strategies between twig and leaf sizes could be adjusted with increasing individual plant competition, thus structuring species coexistence through niche differentiation.     

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).     

Testing of corner’s rules across woody plants in Tiantong region,Zhejiang Province: effects of micro-topography

Aims The size and quantity relationships between twigs and leaves can be used to describe the hydraulic properties of plants in response to environmental stresses. The objective of this study was to examine how twig-leaf relationship would vary with changes in micro-habitat conditions.
Methods The study site is located in the Tiantong National Forest Park (29.87° N, 121.65° E), Zhejiang Province. We measured twig cross-sectional area (twig size), sub-twig cross-sectional area (sub-twig size), individual leaf area, total leaf area (leaf size per twig), the number of twigs at a given twig size (twig intensity), and the number of leaves at a given twig size (leafing intensity) across individual woody plants on 10 plots in each of the convex and concave habitats within an evergreen broad-leaved forest. The standardized major axis (SMA) analysis was conducted to determine the scaling relationships between twig size and leaf size, between sub-twig size and twig intensity, and between leaf size and leafing intensity.
Important findings Significant, positive allometric relationships between twig cross-sectional area and total leaf area were found in plants in both types of micro-habitats (p < 0.001). There was no significant difference between the two micro-habitats in the slope of the regression between twig cross-sectional area and total leaf area, and the common slope of the regressions was significantly greater than 1 (p < 0.001). The intercept was significantlygreater in plants of the concave habitat than in plants of the convex habitat (p < 0.001), indicating that plants in a concave habitat support greater total leaf area at a given twig size than in a convex habitat. Significant, negative allometric scaling relationships were found between twig size and twig intensity in plants in both micro-habitats. There was also no significant difference between the two habitats in the slope of the regression between twig size and twig intensity, and the common slope of the regressions was significantly less than –1 (p < 0.001). The similar intercept in the regression relationship of twig area and twig intensity between the two habitats suggests that plants deploy similar amount of sub-twigs per twig size in both types of habitat. In addition, significant, negative allometric scaling relationships between leaf size and leafing intensity were found to be consistently conserved across micro-habitat types, with the common slope being smaller than –1. A higher value of y-intercept in the scaling relationships of leaf area vs. leafing intensity for plants in the concave habitat indicates that at a given leaf area, more leaves were supported by plants in a concave habitat than in a convex habitat. Overall, plants in a concave habitat tend to deploy more large leaves per twig size than those in a convex habitat. This study demonstrated that both the Corner’s rules and the leaf size-number trade-offs could be generalized to apply at the small local spatial scales. The magnitude and quantitative adjustment of twig-leaf deployment manifests a selection preference of hydraulic properties of plants in coping with changes in water availability between concave and convex habitats.     

武夷山不同海拔黄山松枝叶大小关系

对武夷山自然保护区不同海拔黄山松叶片面积、叶片数量、小枝长度及小枝直径等性状进行测定,分析不同海拔黄山松枝-叶大小间的权衡关系.结果表明: 随海拔升高,黄山松小枝的叶片数量、小枝长度、小枝直径、出叶强度及茎截面积逐渐增大,单叶面积呈逐渐减小趋势;不同海拔黄山松小枝出叶强度与单叶面积均呈显著负相关,不同海拔黄山松小枝茎截面积与总叶面积呈显著正相关;不同海拔黄山松小枝长度、小枝直径与出叶强度呈显著负相关,与单叶面积、叶片数量及总叶面积均呈显著正相关.为提高竞争优势或是资源利用效率,低海拔黄山松倾向于在短枝上着生量少但单叶面积大的针叶,而高海拔黄山松趋向于在长枝上着生量大但单叶面积小的针叶,这体现出不同海拔梯度黄山松小枝的资源利用策略及枝叶间生物量分配的权衡机制.     

Plant phenology,leaf traits and leaf litterfall of contrasting life forms in the arid Patagonian Monte,Argentina

Question: Do coexisting plant life forms differ in overall phenology, leaf traits and patterns of leaf litterfall? Location: Patagonian Monte, Chubut Province, Argentina. Methods: We assessed phenology, traits of green and senesced leaves and the pattern of leaf litterfall in 12 species of coexisting life forms (perennial grasses, deciduous shrubs, evergreen shrubs). Results: We did not identify differences in phenology, leaf traits and patterns of leaf litterfall among life forms but these attributes contrasted among species. Independent of the life form, the maintenance of green leaves or vegetative growth during the dry season was mostly associated with leaves with high leaf mass per area (LMA) and high concentration of secondary compounds. Low LMA species produced low litterfall mass with low concentration of secondary compounds, and high N concentration. High LMA species produced the largest mass of leaf litterfall. Accordingly, species were distributed along two main dimensions of ecological variation, the dimension secondary compounds in leaves ‐ length and timing of the vegetative growth period (SC ‐ VGP) and the dimension leaf mass per area ‐ leaf litterfall mass (LMA ‐ LLM). Conclusions: Phenology, leaf traits and leaf litterfall varied among species and overlapped among life forms. The two dimensions of ecological variation among species (SC ‐ VGP, LMA ‐ LLM) represent distinct combinations of plant traits or strategies related to resource acquisition and drought tolerance which are reflected in the patterns of leaf litterfall.     

Optimisation of spatial allocation patterns in lianas compared to trees used for support

There are only limited possibilities to study the competition between trees and lianas in the top canopy of tropical rain forests. Furthermore, the important question how the leaf traits are related to twig support is rarely studied, especially regarding growing space partitioning between the self-supporting and the climbing growth form. Our study used the hot-air balloon within the “Operation Canopee” in the Masoala National Park, Madagascar, to test the differences in spatial allocation patterns of leaves and twigs in lianas and tree parts used for support. The sampling design emphasised to obtain a common assembly of twigs and leaves from both, trees and lianas. The results from the top canopy were compared to the data from the understorey regarding biomass and nutrients in leaves and distal twigs. In the understorey the reduction in structural investment was much stronger in lianas than in trees. The results showed that lianas reduced carbon investment per volume, but increased leaf nitrogen concentration and leaf area ratio (LAR), the latter driven by a reduction in leaf mass per area (LMA). In the top canopy, lianas contributed about one third of the leaf area density of 3 m² m⁻³. For distal twigs, no relationship was found between twig biomass per volume and leaf area density for trees, but lianas balanced both structural parameters closely. The climbers benefit from the external support provided by the trees and optimise the area of assimilation tissue at low per volume investment for mechanical stability. Several traits such as low LMA and high leaf nitrogen concentrations together with higher LAR and optimised spatial investment advantage the climbing growth form and enable a fast acquisition of growing space. The results emphasize the necessity to consider spatial and structural features of growing space acquisition when dealing with plant competition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

亚热带常绿林不同冠层小枝叶面积-叶生物量关系研究

叶面积与叶生物量的关系对于理解植物叶片的碳收益和投资权衡策略具有重要意义。收益递减假说认为植物的叶面积与叶生物量成显著异速生长关系，其异速生长指数<1.0，但该假说是否适用于不同生活型（常绿与落叶）亚热带木本植物不同冠层高度（上下冠层）当年生小枝的叶片仍不清楚。以江西亚热带常绿阔叶林的69种常绿与落叶木本植物当年生小枝上的叶为研究对象，采用标准化主轴回归估计（standardized major axis estimation，SMA）方法检验不同冠层高度和生活型叶面积与叶生物量的异速生长关系。结果显示：（1）当年生小枝叶生物量在不同冠层高度和生活型的植物中无显著差异（P>0.05），叶面积在常绿和落叶植物中有显著差异（P<0.05），常绿和落叶植物的比叶重存在显著差异（P<0.05），而落叶植物的比叶重在不同冠层高度存在显著差异（P<0.05），同一冠层，常绿植物比叶重显著高于落叶植物（P<0.05）；（2）69种植物的叶面积与叶生物量异速生长指数具有物种特异性，60.9%的物种叶面积与叶生物量呈等速生长关系；（3）不同冠层和生活型植物的叶面积与叶生物量呈等速生长关系，但其异速生长常数在不同冠层高度与生活型间存在差异。这些结果表明冠层高度和生活型未改变叶面积-生物量之间的等速生长关系，不支持"收益递减"假说。     

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.