Leaf structure of Syzygium spp. (Myrtaceae) in relation to site affinity within a tropical rain forest

This study examined four species of Syzygium (S. firmum, S. makul, S. operculatum, S. rubicundum) Myrtaceae, a tree genus that dominates the canopy of rain forests of south‐west Sri Lanka. Syzygium spp. occupy differing habitats with relation to succession and forest topography. We examined differences in leaf morphology and physiology in response to amount of shade, an important environmental variable affecting Syzygium distribution within the forest. To study change in leaf structure and physiology, environmental shelters were constructed simulating forest shade that differed in quality, quantity and duration. Seedlings were exposed to: (i) 0% shade (full sun, FS), red : far red (R : FR) ratio 1.27; (ii) 65% shade (large opening, LO) with direct sunlight similar to the centre of a large canopy opening, R : FR ratio 1.27; (iii) 82% shade (small opening, SO) with direct sunlight similar to the centre of a small canopy opening, R : FR ratio 1.27; (iv) 58% uniform light shade (LS) with a quality similar to the outside edge of a large canopy opening, R : FR ratio 1.05; (v) 85% uniform medium shade (MS) with a quality similar to the inside forest edge of a large canopy opening, R : FR ratio 0.97; (vi) 99% uniform deep shade (DS) similar to that of the forest understorey, R : FR ratio 0.23. The shelters were constructed in a large open area at the field station of the Sinharaja World Heritage site, Sri Lanka. Seedlings of each species were grown for two years in their respective shade treatments before physiological, morphological and anatomical measurements were made on leaves. Variation in leaf structure and physiology between the species was associated with differences in shade‐tolerance and water‐use. All species increased in photosynthesis rates and dimensions in leaf structure (leaf blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll) with decrease in shade. In contrast, stomatal conductivity was highest in the DS (99% shade) treatment. Leaves of Syzygium firmum were thickest and largest in area. S. firmum also had highest photosynthesis in the SO (82% shade) treatment. S. firmum was the most shade‐tolerant of all species: it grows well in low shade and its leaf structure suggests it to be the most conservative in water‐use of the Syzygium spp. In the forest S. firmum can persist in the forest shade as established seedlings, but grows best within canopy openings of late‐seral rain forest. Leaves of S. operculatum were thinnest but had highest stomatal densities of the four species. S. operculatum is considered shade‐intolerant, with a leaf structure suggesting it to be prone to desiccation, and by implication susceptible to drought. S. operculatum is found along streams within early seral rain forest habitat, often originating on stream banks after land clearance for cultivation. In the FS (0% shade) treatment, S. rubicundun had highest photosynthesis rates and greatest number of leaves but smallest leaf area of the Syzygium species. S. rubicundum is more shade‐intolerant but more efficient in water‐use than S. operculatum. S. rubicundum is a mid‐seral canopy tree of the midslope stands that are thought to have originated after catastrophic windthrows or swidden cultivation. The leaf physiology and structure of S. makul suggests it to be both moderately shade‐tolerant and conservative in water‐use. It is the most widely distributed Syzygium species across the topography of late‐seral rain forest. We suggest forest disturbance and hydrology are important environmental factors that influence distribution of Syzygium species across the topography. Results from this study contribute to a body of knowledge suggesting that canopy tree species of rain forests in south‐west Sri Lanka have discrete affinities to topography and differences in successional status, and that adaptations in leaf structure and physiology are indicative of such phenomena. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 141 , 365–377.     

生长型分类方案不同导致森林生态系统植物功能性状的统计偏差

将植物划分为不同的生长型来统计植物功能性状特征,是当前植物性状研究中常用的方法;但生长型分类方案的不同很可能造成植物功能性状统计分析的偏差,对此偏差的评估却尚未见报道。根据植物志描述及野外调查实际情况,将生长型划分为3种不同的分类方案：分类1：根据植物志信息划分为传统意义的乔木和灌木;分类2：根据树高和胸径划分乔木、小乔木和灌木;分类3：仅根据树高划分乔木层与灌木层的乔木和灌木。以东部亚热带常绿阔叶林区域的浙江金华北山35种优势阔叶木本植物的枝叶性状为研究对象,比较不同生长型分类对植物枝叶性状统计数据的影响。结果表明：（1）与传统的分类1相比,分类2对乔木植物枝叶性状影响的显著程度要高于分类3,而对灌木植物枝叶性状的影响程度低于分类3;但不同生长型分类方案中乔木和灌木的枝叶性状总体差异不显著。而与分类2小乔木相比,分类1以及分类2内部的乔木和灌木生长型的性状与分类2小乔木差异非常明显;（2）将不同生长型植物再划分为不同生活型后,不同生长型分类方案对性状统计的影响增大。无论是常绿还是落叶生活型的小乔木,其与不同生活型乔木和灌木的性状差异仍然显著。可见,不同的生长型分类方案可造成植物功能性状统计的差异;把小乔木植物这一功能类群划分出来,能更好地反映森林生态系统性状特征的差异性。     

Leaf traits from stomata to morphology are associated with climatic and edaphic variables for dominant tropical forest evergreen oaks

热带森林优势种青冈叶片气孔、解剖和形态性状与气候、土壤因子的关联 了解优势树种叶片多水平的功能性状沿海拔梯度的变化及其内在关联,有助于预测优势种应对气候变化的响应与适应。本文研究了青冈属树种叶片气孔、解剖和形态性状沿海拔梯度的变化及其与环境调控因子的关联,探究了其生态策略是否随海拔发生改变。在海南尖峰岭热带森林,沿海拔梯度(400–1400 m)采集了6种常绿青冈：竹叶青冈(Cyclobalanopsis bambusaefolia)、雷公青冈(C. hui)、托盘青冈 (C. patelliformis)、饭甄青冈(C. fleuryi)、吊罗山青冈(C. tiaoloshanica)和亮叶青冈(C. phanera)叶片,用于气孔、解剖和形态性状的测定。研究结果表明,随海拔升高,青冈树种叶片气孔密度、气孔孔隙度指数和叶面积显著增加,但海绵组织厚度比和干物质含量则显着降低。叶片气孔、解剖和形态性状沿海拔梯 度的变化主要受年均温、年降水量和土壤pH 值调控。在低海拔和高海拔处,青冈属采取“耐受”和“竞 争”策略,而在中海拔处,则是“竞争”策略。土壤磷含量和土壤pH 值随海拔的变化可能是驱动其生态 策略转变的主要原因。该结果揭示,热带森林优势树种青冈可通过从气孔细胞-组织解剖结构-叶片水平功能性状的改变来响应环境变化。     

Liana community and functional trait analysis in tropical dry evergreen forest of India

Aim Lianas are abundant and diverse throughout the world and constitute an important structural and functional component of tropical forests. This study aims to investigate liana diversity, abundance and their functional traits in Indian tropical dry evergreen forest (TDEF).Methods A total of ten 1-ha plots, one each in 10 Indian TDEF sites were demarcated. Each 1-ha plot was divided into one-hundred 10- × 10-m quadrats to facilitate woody species inventory. All lianas ≥1cm diameter measured at 130cm from the rooting point and all trees ≥10-cm girth at breast height (gbh) were recorded from the study sites to analyze the patterns of liana diversity and abundance and also to compare the contribution of lianas to the total woody species richness, density and basal area. Liana variables across the study sites were compared using one-way analysis of variance. The qualitative functional traits of inventoried lianas and trees were assessed on the field and referring to pertinent field manuals.Important findings A total of 9237 liana individuals (ranged from 408–1658 individuals ha^-1) representing 52 species, 45 genera and 28 families were encountered from the 10 study sites. Liana species richness ranged from 11–31 species ha^-1 in 10 sites, which averaged 23.4 (±5.7) species ha^-1. The total basal area of lianas in the study sites was 7. 3 m 2 (0.20–1.76 m 2 ha^-1). There was a significant variation in liana species richness, density and basal area across the studied sites. On the whole, lianas contributed 52%, 49.3% and 4.1% to the total woody species (lianas and trees) richness, density and basal area, respectively. Liana trait analysis revealed the majority (50%) of lianas belonged to brevi-deciduous type. Stem twining was the chief climbing mechanism, exhibited by 21 species (52.6% of total abundance). More than half of the liana species (34 species; 6925 individuals) had microphyllous leaves. Fleshy-fruited lianas mostly bearing berries and drupes constituted the major fruit type in the studied sites. Zoochory was the predominant dispersal mode observed in 63.4% of species. Considering the ecological and functional role of lianas in Indian TDEF, the need for conservation is emphasized.     

温带针阔混交林叶片性状随树冠垂直高度的变化规律

自然界中,森林植物叶片的生长随树冠高度呈现明显的垂直分布现象;然而,有关叶片性状随着树冠垂直高度增加的变化规律仍不清楚。为了更好地揭示植物叶片对光环境变化的适应策略以及对资源的利用能力,有必要深入探讨叶片性状与冠层高度的定量关系及其内在调控机制。以中国广泛分布的温带针阔混交林为对象,选取8种主要树种为研究对象(白桦、蒙古栎、水曲柳、大青杨、色木槭、千金榆、核桃楸和红松),通过测定这些物种9个冠层高度的叶片比叶面积(SLA)、叶片干物质含量(LDMC)、叶片氮含量(N)、叶片磷含量(P)、氮磷比(N∶P)和叶绿素含量(Chl)等属性,探讨了针阔混交林叶片性状的差异以及各性状之间的相关关系,进而揭示叶片性状随树冠垂直高度的变化规律。实验结果表明:1)温带针阔混交林内优势树种的部分叶片性状在不同冠层高度之间差异显著。2)随着树冠垂直高度的增加,SLA、LDMC、N、P、N∶P和Chl呈现不同的变化趋势。其中,阔叶树种SLA随着树冠垂直高度的增加而减小;所有树种的LDMC随着树冠垂直高度的增加而增加;不同树种的N、P、N∶P和Chl随着树冠垂直高度的变化规律存在差异。3)对于温带针阔混交林冠层中,SLA与N、P、N∶P均存在显著的正相关关系,高SLA伴随着高的N、P、N∶P,表明植物通过SLA与N、P等性状的协同来提高叶片的光合作用(或对光热资源的利用效率)。本研究通过定量分析探讨温带针阔混交林叶片性状随冠层高度的变化规律,一定程度地揭示了树木对光、热和水资源竞争的适应机制,以及植物叶片的资源利用和分配策略,不仅拓展了传统性状研究的范畴,其相关研究结论也有助于树木生长模型的构建和优化。     

海南岛热带山地雨林幼苗幼树光合与叶氮、叶磷及比叶面积的关系

以海南岛吊罗山热带山地雨林101个物种的幼苗幼树为试验材料,测定其光合、叶片氮、磷含量及比叶面积;检验其相关关系,并按乔木,乔灌木(小乔木至大灌木)和灌木3个生活型组进行分组检验。研究结果表明,单位叶面积(Aarea)和单位叶重量的光合速率(Amass)均表现出灌木>乔木>乔灌木,方差分析表明,灌木和乔灌木之间Aarea差异显著;灌木和乔木以及灌木和乔灌木之间Amass差异显著(p<0.05)。Aarea与叶氮含量之间的相关性在不同生态型组和所有物种之间均达到极显著水平(p<0.0001);与叶磷之间的相关关系在灌木(p=0.0038),乔灌木(p=0.0002)以及所有物种(p<0.0001)之间达到极显著水平,但是在乔木中未达到显著水平(p>0.05);与SLA之间在灌木(p=0.0006)、乔木(p<0.0001)和所有物种(p<0.0001)之间达到极显著水平,但是在乔灌木中未达到显著水平(p>0.05)。Amass与叶片氮含量、SLA的相关关系在不同生活型组和所有物种中都达到极显著水平(p<0.0001);与叶磷含量之间的相关性在灌木(p=0.0004),乔灌木(p=0.0018)及所有物种(p<0.0001)中极显著,在乔木生活型组中也达显著水平(p=0.0377)。逐步回归表明,与Aarea相比,Amass估计结果更接近于实际测值。由此可见,海南岛热带山地雨林林下幼苗幼树的光合和叶氮、磷含量及SLA之间相关关系与基于成树的研究非常相似,并且A比A更能稳定体现这种相关性。     

尖峰岭热带山地雨林林冠层乔木某些功能性状的系统发育信号、关联性及其演化模式

热带雨林林冠层具有丰富的物种、功能和系统发育(谱系)多样性,能够显著影响生态系统生物地球化学循环,调节大气水热平衡,缓解气候变化与人为干扰的负面作用。因此热带雨林林冠层功能和谱系生态学研究是目前群落生态学研究的热点之一。选取海南尖峰岭热带山地雨林3个1 hm2样地的林冠层为研究对象,利用样地林冠树种清查数据基于APG III系统发育结构重建样地林冠层系统发育树。利用Blomber's K对和Pagel'sλ指标结合系统发育独立性比较法对组成林冠层乔木树种的结构、化学计量和水力学功能性状(11个性状)的系统发育信号、关联性和演化模式进行研究,以探讨物种亲缘关系对尖峰岭热带山地雨林林冠层多维功能性状关联性及其动态演化的影响。结果表明,有8个功能性状(叶面积、叶厚度和潜在最大高度除外)具有显著的系统发育信号(通过P0.05的显著性检验),Blomber's K值和Pagel'sλ值分别介于0.202—0.392和0.277—0.847之间,表明尖峰岭热带山地雨林林冠层功能性状普遍存在系统发育保守性。在系统发育背景下,林冠层乔木树种结构、化学和水力学功能性状在物种水平普遍存在显著关联性(P0.05),表现出趋同或趋异进化;而且林冠层乔木随物种分化其功能性状分化模式大致呈水平"漏斗"状,姐妹类群功能性状间差异性在物种分化早期(大约1亿2千万年前至6000万年前)明显小于其在中后期(大约6000万年前至今)的差异性,导致了林冠层性状空间在中后期迅速膨大。然而林冠层主要功能性状在系统发育树内部每一节点上姊妹类群分化产生的系统发育独立性比较值绝大部分与零模型随机模拟值并无显著性差异。了解系统发育背景下林冠层功能性状的权衡关系及其随物种演化的分化模式与时间动态为进一步探究热带雨林林冠生态系统功能发挥奠定基础。     

Leaf traits and herbivory rates of tropical tree species differing in successional status

We evaluated leaf characteristics and herbivory intensities for saplings of fifteen tropical tree species differing in their successional position. Eight leaf traits were selected, related to the costs of leaf display (specific leaf area [SLA], water content), photosynthesis (N and P concentration per unit mass), and herbivory defence (lignin concentration, C:N ratio). We hypothesised that species traits are shaped by variation in abiotic and biotic (herbivory) selection pressures along the successional gradient. All leaf traits varied with the successional position of the species. The SLA, water content and nutrient concentration decreased, and lignin concentration increased with the successional position. Herbivory damage (defined as the percentage of damage found at one moment in time) varied from 0.9-8.5% among the species, but was not related to their successional position. Herbivory damage appeared to be a poor estimator of the herbivory rate experienced by species, due to the confounding effect of leaf lifespan. Herbivory rate (defined as percentage leaf area removal per unit time) declined with the successional position of the species. Herbivory rate was only positively correlated to water content, and negatively correlated to lignin concentration, suggesting that herbivores select leaves based upon their digestibility rather than upon their nutritive value. Surprisingly, most species traits change linearly with succession, while resource availability (light, nutrients) declines exponentially with succession.     

Leaf litter arthropod responses to tropical forest restoration

Soil and litter arthropods represent a large proportion of tropical biodiversity and perform important ecosystem functions, but little is known about the efficacy of different tropical forest restoration strategies in facilitating their recovery in degraded habitats. We sampled arthropods in four 7‐ to 8‐year‐old restoration treatments and in nearby reference forests. Sampling was conducted during the wet and dry seasons using extractions from litter and pitfall samples. Restoration treatments were replicated in 50 × 50‐m plots in four former pasture sites in southern Costa Rica: plantation – trees planted throughout the plot; applied nucleation/islands – trees planted in patches of different sizes; and natural regeneration – no tree planting. Arthropod abundance, measures of richness and diversity, and a number of functional groups were greater in the island treatment than in natural regeneration or plantation treatments and, in many cases, were similar to reference forest. Litter and pitfall morphospecies and functional group composition in all three restoration treatments were significantly different than reference sites, but island and plantation treatments showed more recovery than natural regeneration. Abundance and functional group diversity showed a much greater degree of recovery than community composition. Synthesis and applications: The less resource‐intensive restoration strategy of planting tree islands was more effective than tree plantations in restoring arthropod abundance, richness, and functional diversity. None of the restoration strategies, however, resulted in similar community composition as reference forest after 8 years of recovery, highlighting the slow rate of recovery of arthropod communities after disturbance, and underscoring the importance of conservation of remnant forests in fragmented landscapes.     

Vertical stratification of feeding guilds and body size in beetle assemblages from an Australian tropical rainforest

Abstract The vertical stratification of insect species assemblages inhabiting tropical rainforests is well established but few have examined whether these patterns are reflected in vertical stratification of body size or feeding guilds. We used Malaise and Flight Interception Traps to sample beetle assemblages from five locations, at both canopy and ground zones of a tropical lowland rainforest site near Cape Tribulation, Australia. Beetles from 4 years of sampling were sorted to Family and morphospecies, and allocated to one of five feeding guilds. Within feeding guilds the number of species and individuals, from canopy‐ and ground‐caught traps were compared. The body lengths of species were measure and compared within feeding guilds and families. Herbivores was the dominant guild but was not the majority of all species or individuals. Most beetle species (69%) were less than 5 mm in length and the mean size of canopy‐caught species was greater than that for ground‐caught species. This was probably due to slightly more species of plant feeders (herbivores and xylophages) present in the canopy, which were significantly larger than saprophages, fungivores and predators. Among feeding guilds, there were few overall canopy–ground differences. These results contrast with species composition results presented elsewhere where strong differences between the canopy and the ground were evident. We suggest that our guild groupings may have been too coarse to detect fine‐scale differences and that resource partitioning may have also masked faunal stratification. We propose that fine‐scale differences in resources between the canopy and the ground, together with strong microclimate gradients, are likely to be important in structuring the vertical stratification of insect assemblages at the level of species, but not with respect to functional groups.     

大青沟自然保护区主要森林群落优势种的叶性状

植物功能性状是近年来生态学研究的热点。其中叶功能性状与植株生物量和植物对资源的获得、利用及利用效率的关系最为密切。大青沟森林植物群落分布于科尔沁沙地,生境条件非常特殊,在沙沟里存在着一片茂密的森林,与周围浩瀚无垠的沙坨景观形成极为鲜明的对照。从沟底到沟顶,虽然海拔高度仅相差六、七十米,但由于距离沟底水源不同,土壤条件差异大,形成了不同的森林植物群落类型。大果榆群落、蒙古栎群落和水曲柳群落分别分布在大青沟自然保护区的沟顶、沟中和沟底。为了对大青沟自然保护区,不同环境梯度下的森林植物群落叶片功能性状进行研究,以大青沟自然保护区大果榆、蒙古栎、水曲柳3种主要森林群落为研究对象,分别测定不同群落优势种的叶厚度、比叶面积、叶干物质含量、叶大小和叶干重等5项叶功能性状,研究叶功能性状之间的关系,并对不同生长型、不同群落叶功能性状进行比较。相关分析结果表明,叶厚度与比叶面积呈极显著负相关,与叶大小和叶干重呈极显著正相关;比叶面积与叶干物质含量、叶干重呈极显著负相关,与叶大小呈显著正相关;叶干物质含量与叶大小呈极显著负相关,与叶干重呈极显著正相关;叶大小与叶干重呈极显著正相关。不同生长型植物叶片性状的分析表明,草本植物的叶干物质含量比乔木和灌木低,而其比叶面积高于乔木和灌木;对不同群落叶功能性状进行比较发现,大果榆群落和蒙古栎群落乔木、灌木叶厚度与干物质含量显著高于水曲柳群落的叶厚度与干物质含量,二者比叶面积显著低于水曲柳群落。大果榆群落和蒙古栎群落从叶功能性状的角度,它们具有较高的叶干物质含量和较低的比叶面积,体现出适应干旱生境叶片的特征。水曲柳群落呈现出低叶干物质含量、高比叶面积的特征,体现出适应湿润、土壤水分较好生境的特征。不同群落通过调节自身的物种组成,形成不同的功能性状组合来适应环境。     

云南热带季雨林及其与热带雨林植被的比较

在中国植物学文献中, 对热带季雨林的解释和运用是不一致的, 特别是易于把季雨林与热带雨林相混淆。季雨林是在具有明显干、湿季变化的热带季风气候下发育的一种热带落叶森林植被, 是介于热带雨林与热带稀树草原(savanna)之间的一个植被类型。云南的热带季雨林在分布生境、生态外貌特征、植物种类组成和地理成分构成上, 均与热带雨林有明显区别, 季雨林主要分布在海拔1 000 m以下的几大河流开阔河段两岸和河谷盆地, 其群落结构相对简单, 乔木一般仅有1至2层, 上层树种在干季落叶或上层及下层树种在干季都落叶; 在生活型组成上, 季雨林的木质藤本相对较少, 大高位芽植物及地上芽植物很少, 但地面芽植物很丰富, 地下芽植物和一年生植物也相对丰富; 在叶级和叶型特征上, 季雨林植物的小叶和复叶比例相对较高, 分别占到24%和44%; 在植物区系地理成分构成上, 季雨林的热带分布属合计也占绝对优势, 但以泛热带分布属的比例相对较高, 约占到总属数的30%, 热带亚洲至热带非洲分布属的比例也较高, 约占总属数的12%。季雨林的地理成分更为多样性, 起源与发展历史也更复杂和古老。     

Contrasting leaf chemical traits in tropical lianas and trees: implications for future forest composition

Lianas are an important growthform in tropical forests, and liana abundance and biomass may be increasing in some regions. Explanations for liana proliferation hinge upon physiological responses to changing resource conditions that would favour them over trees. Testing a chemical basis for such responses, we assessed 22 foliar traits in 778 lianas and 6496 trees at 48 tropical forest sites. Growthform differences in chemical allocation occurred on a leaf mass and area basis. Light capture-growth and maintenance-metabolism chemicals averaged 14.5 and 16.7% higher mass-based concentration in lianas than in trees globally, whereas structure and defence chemicals averaged 9.0% lower in lianas. Relative differences in chemical allocation by lianas and trees were mediated by climate with peak differences at about 2500 mm year(-1) and 25 °C. Differences in chemical traits suggest that liana expansion could be greatest in forests undergoing increased canopy-level irradiance via disturbance and climate change.     

Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species

The effect of leaf aging on photosynthetic capacities was examined for upper canopy leaves of five tropical tree species in a seasonally dry forest in Panama. These species varied in mean leaf longevity between 174 and 315 d, and in maximum leaf life span between 304 and 679 d. The light-saturated CO2 exchange rates of leaves produced during the primary annual leaf flush measured at 7-8 mo of age were 33-65% of the rates measured at 1-2 mo of age for species with leaf life span of < 1 yr. The negative regression slopes of photosynthetic capacity against leaf age were steeper for species with shorter maximum leaf longevity. In all species, regression slopes were less steep than the slopes predicted by assuming a linear decline toward the maximum leaf age (20-80% of the predicted decline rate). Maximum oxygen evolution rates and leaf nitrogen content declined faster with age for species with shorter leaf life spans. Statistical significance of regression slopes of oxygen evolution rates against leaf age was strongest on a leaf mass basis (r = 0.49-0.87), followed by leaf nitrogen basis (r = 0.48-0.77), and weakest on a leaf area basis (r = 0.35-0.70).     

Leaf habit does not predict leaf functional traits in cerrado woody species

Plant species with a high leaf life span (LLS) commonly have a low specific leaf area (SLA), leaf nitrogen per unit mass (N), and phosphorous concentration (P), whereas species with low LLS have a high SLA, N and P. However, LLS tends to be longer in species growing in low-nutrient soils and, therefore, differences in LLS and other leaf traits may not be consistent with a plant classification according to leaf habit. Here we investigated whether leaf habit is consistent with leaf economic spectrum trade-offs in cerrado (a Neotropical savanna) woody species. We analyzed the SLA, N and P of 125 woody species with a distinct leaf habit (deciduous, semideciduous, brevideciduous or evergreen). We also gathered data on the LLS (33 species), maximum net photosynthesis per leaf area (A_area, 56 species) and per leaf mass (A_mass, 31 species), comprising the most extensive database analyzed so far for the cerrado. Differences among leaf habit groups were tested using generalized linear mixed models and ANOVA. We did not find differences in SLA and N among species with a distinct leaf habit, but deciduous species had a higher leaf P concentration than evergreens. Species did not differ in LLS and A_mass, but A_area varied among groups. Semideciduous species had higher A_area values than deciduous and brevideciduous species, but all other groups had similar A_area values. Because of the small difference in the LLS, SLA, leaf N, leaf P and maximum net photosynthesis, we argue that deciduous, brevideciduous, semideciduous and evergreen species may not constitute different functional groups in cerrado woody species.     

Hydraulic and photosynthetic co-ordination in seasonally dry tropical forest trees

In the present study the linkage between hydraulic, photosynthetic and phenological properties of tropical dry forest trees were investigated. Seasonal patterns of stem‐specific conductivity (K_SP) described from 12 species, including deciduous, brevi‐deciduous and evergreen species, indicated that only evergreen species were consistent in their response to a dry‐to‐wet season transition. In contrast, K_SP in deciduous and brevi‐deciduous species encompassed a range of responses, from an insignificant increase in K_SP following rains in some species, to a nine‐fold increase in others. Amongst deciduous species, the minimum K_SP during the dry season ranged from 6 to 56% of wet season K_SP, indicating in the latter case that a significant portion of the xylem remained functional during the dry season. In all species and all seasons, leaf‐specific stem conductivity (K_L) was strongly related to the photosynthetic capacity of the supported foliage, although leaf photosynthesis became saturated in species with high K_L. The strength of this correlation was surprising given that much of the whole‐plant resistance appears to be in the leaves. Hydraulic capacity, defined as the product of K_L and the soil–leaf water potential difference, was strongly correlated with the photosynthetic rate of foliage in the dry season, but only weakly correlated in the wet season.