Variation In Leaf Traits Research Articles

Leaf functional trait variation in a humid temperate forest, and relationships with juvenile tree light requirements.

The species-rich arborescent assemblages of humid tropical forests encompass much of the known range of the leaf economics spectrum, often including >20-fold variation in leaf lifespan. This suite of traits underpins a life-history continuum from fast-growing pioneers to slow-growing shade-tolerant species. Less is known about the range of leaf traits in humid temperate forests, and there are conflicting reports about relationships of these traits with the light requirements of temperate evergreen angiosperms. Here I quantify the range of leaf functional traits in a New Zealand temperate evergreen forest, and relationships of these traits with light requirements of juvenile trees and shrubs. Foliage turnover of saplings of 19 evergreen angiosperms growing beneath gaps (12–29% canopy openness) and in understories (1.2–2.9%) was measured over 12 months. Dry mass per area (LMA), dry matter content, thickness, density and nitrogen content (N) of leaves were also measured. Species minimum light requirements were indexed as the 10th percentile of the distribution of saplings in relation to canopy openness. Interspecific variation of leaf lifespan was ∼6-fold in gaps (0.6 to 3.8 yrs), and ∼11-fold in the understorey (0.7 to 7.7 yrs). Six small tree and shrub species are effectively leaf-exchangers, with leaf lifespans of c.1 year in gaps—albeit usually longer in the shade. Interspecific variation in other leaf traits was 2.5 to 4-fold. Lifespans and LMA of both sun and shade leaves were negatively correlated with species light requirements i.e., positively correlated with shade tolerance. However, light environment (gap vs shade) explained about the same amount of variation in LMA as species’ identity did. Species light requirements were not significantly correlated with leaf N, dry matter content, density or thickness—except for a marginally significant correlation with dry matter content of shade leaves. Species light requirements were thus less consistently related to leaf structural traits than appears to be the case in humid tropical forests. Whereas the wide interspecific variation in leaf economic traits of tropical rainforest species outweighs plastic response to light availability, temperate evergreen woody angiosperms appear to occupy a narrower range of the leaf economic spectrum. Standardization of the light environments in which LMA is measured is vital in comparative studies of humid temperate forest evergreens, because of countergradient responses of this trait to light, and because of the relative magnitudes of plastic and interspecific variation in LMA in these forests.

Global patterns of intraspecific leaf trait responses to elevation.

Elevational gradients are often used to quantify how traits of plant species respond to abiotic and biotic environmental variations. Yet, such analyses are frequently restricted spatially and applied along single slopes or mountain ranges. Since we know little on the response of intraspecific leaf traits to elevation across the globe, we here perform a global meta-analysis of leaf traits in 109 plant species located in 4 continents and reported in 71 studies published between 1983 and 2018. We quantified the intraspecific change in seven morpho-ecophysiological leaf traits along global elevational gradients: specific leaf area (SLA), leaf mass per area (LMA), leaf area (LA), nitrogen concentration per unit of area (Narea), nitrogen concentration per unit mass (Nmass), phosphorous concentration per unit mass (Pmass) and carbon isotope composition (δ13 C). We found LMA, Narea, Nmass and δ13 C to significantly increase and SLA to decrease with increasing elevation. Conversely, LA and Pmass showed no significant pattern with elevation worldwide. We found significantly larger increase in Narea, Nmass, Pmass and δ13 C with elevation in warmer regions. Larger responses to increasing elevation were apparent for SLA of herbaceous compared to woody species, but not for the other traits. Finally, we also detected evidences of covariation across morphological and physiological traits within the same elevational gradient. In sum, we demonstrate that there are common cross-species patterns of intraspecific leaf trait variation across elevational gradients worldwide. Irrespective of whether such variation is genetically determined via local adaptation or attributed to phenotypic plasticity, the leaf trait patterns quantified here suggest that plant species are adapted to live on a range of temperature conditions. Since the distribution of mountain biota is predominantly shifting upslope in response to changes in environmental conditions, our results are important to further our understanding of how plants species of mountain ecosystems adapt to global environmental change.

Influence of dry season on Quercus suber L. leaf traits in the Iberian Peninsula.

Water deficit and drought conditions are increasing in intensity, frequency, and duration in the Iberian Peninsula. We observed natural variation in leaf traits across the range of Quercus suber L. (cork oak), an ecologically important species within this region. Stomatal traits (e.g., pore length, maximum aperture) and carbon isotope composition (δ13 C) provide an opportunity to examine the integrative effects of drought and dry-season intensity on leaf development, maximum stomatal conductance, and adaptation to precipitation regimes. Gross leaf traits (e.g., area, thickness), stomatal traits (e.g., pore length, size, aperture), and carbon isotope discrimination were measured in Q. suber leaves, and maximum stomatal conductance to water vapor (gwmax ) was calculated. Trees were sampled from nine natural populations across a climate gradient in the Iberian Peninsula, including trees from two genetic lineages. Linear mixed models compared total water deficit to leaf traits, accounting for tree and site as random effects. Quercus suber gross leaf morphology remained consistent across the climate gradient, but increasing water deficit was correlated with smaller stomata at the leaf level and low δ13 C at the tree level. No traits were significantly different between the two genetic lineages. While there were no significant differences in gross leaf morphology across the climate gradient or between the genetic lineages, stomatal traits and δ13 C responded to climate, suggesting that Q. suber can inhabit a range of environments in the Iberian Peninsula via micro-adjustments of the trait that controls water loss into the atmosphere.

Neither species geographic range size, climatic envelope, nor intraspecific leaf trait variability capture habitat specialization in a hyperdiverse Amazonian forest

AbstractMany plant species exhibit strong association with topographic habitats at local scales. However, the historical biogeographic and physiological drivers of habitat specialization are still poorly understood, and there is a need for relatively easy‐to‐measure predictors of species habitat niche breadth. Here, we explore whether species geographic range, climatic envelope, or intraspecific variability in leaf traits is related to the degree of habitat specialization in a hyperdiverse tropical tree community in Amazonian Ecuador. Contrary to our expectations, we find no effect of the size of species geographic ranges, the diversity of climate a species experiences across its range, or intraspecific variability in leaf traits in predicting topographic habitat association in the ~300 most common tropical tree species in a 25‐ha tropical forest plot. In addition, there was no phylogenetic signal to habitat specialization. We conclude that species geographic range size, climatic niche breadth, and intraspecific variability in leaf traits fail to capture the habitat specialization patterns observed in this highly diverse tropical forest.

Short Communication: Investigation of leaf architectural patterns: Implications in delineating taxonomically controversial Hoya merrillii Schlechter and Hoya quinquenervia Warburg

Abstract. Paguntalan DP, Buot JrIE. 2019. Short Communication: Investigation of leaf architectural patterns: Implications in delineating taxonomically controversial Hoya merrillii Schlechter and Hoya quinquenervia Warburg. Biodiversitas 20: 833-839. Variations in leaf traits of two very likely similar plants, Hoya merrillii Schlechter and Hoya quinquenervia Warburg were examined together with an outgroup, Hoya cagayanensis Burton. The objectives of the study are to examine the leaf architectural characteristics of Hoya merrillii and Hoya quinquenervia and use the information as an additional basis of delineation between the said species of Hoya plants. Thirty leaf samples for each species were examined for laminal and vein characters. The characters laminar size, laminar shape, number of basal veins, quinternary vein fabric, areole development and characteristics of FEVs (free-ending veins), were well-defined from either one or both species. Overall, the results showed variability between the studied plant groups using univariate and multivariate analysis. The data ordination on the morphometric traits using PCOa showed distinct groupings among studied leaf samples and yielded consistent results with the single linkage or nearest neighbor cluster dendrogram which showed distinct clustering of individual species in terms of morphometric traits that were considered in the study. Detected variations of the leaf architectural traits on the leaves of Hoya merrillii Schlechter and Hoya quinquenervia Warburg allowed for the more available basis of separation in addition to established floral morphologies that are primarily used as criteria for delineation between species. Variations in leaf architecture characters can be of great value to illustrate or imply meanings in the taxonomic relationships of the Hoya species studied.

The interplay among intraspecific leaf trait variation, niche breadth and species abundance along light and soil nutrient gradients

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among‐plot ITV, 2) a strong relationship between trait values and the environment, and 3) a close fit between traits and local environment trait optima. We measured leaf functional traits (leaf area, LMA, leaf N and P concentrations) of saplings in woody species, and compared the relative abundance of each species with its niche breadth, measured as the range of light, soil N and P availability. We used the slope of the linear regression of species’ trait–environment relationships to assess the strength and direction of these relationships, and measured the degree to which species’ trait values track the environmental optimum across plots. In some cases, species having wide niche breadth had high ITV in leaf N and also matched traits (LMA and leaf P) to local optima along the light gradient; they also had high ITV in general and matched leaf P to local optima along the soil P gradient. The relationship between species with wide niche breadth and the strength of intraspecific trait–environment relationships was generally weak and varied depending on the niche dimension and trait in question. Species varied considerably in the strength of trait–environment relationships and total magnitude of ITV, and this variation was not generally strongly related to species abundances or niche breadth patterns. In conclusion, trait variation at the community level is not driven by a few abundant, widely distributed species, but depends on the aggregate trait responses of both abundant and rare species. This makes it difficult to scale individual species trait responses up to the community level.

The Smaller the Leaf Is, the Faster the Leaf Water Loses in a Temperate Forest.

Leaf size (i.e., leaf surface area and leaf dry mass) profoundly affects a variety of biological carbon, water and energy processes. Therefore, the remarkable variability in individual leaf size and its trade-off with total leaf number in a plant have particularly important implications for understanding the adaption strategy of plants to environmental changes. The various leaf sizes of plants growing in the same habitat are expected to have distinct abilities of thermal regulation influencing leaf water loss and shedding heat. Here, we sampled 16 tree species co-occurring in a temperate forest in northeastern China to quantify the variation of leaf, stomata and twigs traits, and to determine the relationships of leaf size with leaf number and leaf water loss. We examined the right-skewed distributions of leaf size, leafing intensity, stomatal size and stomatal density across species. Leafing intensity was significantly negatively correlated with leaf size, accounting for 4 and 12% of variation in leaf area and leaf mass, respectively. Species was the most important factor in explaining the variation in leaf size (conditional R2 of 0.92 for leaf area and 0.82 for leaf mass). Leaf area and mass significantly increased with increasing diameter of twigs. Leaf water loss was strongly negatively correlated with leaf area and leaf mass during the first four hours of the measurement. Leaf area and leaf mass accounted for 38 and 30% of variation in total leaf water loss, respectively. Leaf water loss rate (k) was significantly different among tree species and markedly linearly decreased with increasing leaf area and leaf mass for simple-leaved tree species. In conclusion, the existence of a cross-species trade-off between the size of individual leaves and the number of leaves per yearly twig unit was confirmed in that temperate forest. There was strongly negative correlation between leaf water loss and leaf size across tree species, which provides evidences for leaf size in leaf temperature regulation in dry environment with strong radiation. The size-dependent leaf water relation is of central importance to recognize the functional role of leaf size in a changing climate including rapid changes in air temperature and rainfall.

Forest diversity effects on insect herbivores: do leaf traits matter?

Summary Insect herbivore damage and abundance are often reduced in diverse plant stands. However, few studies have explored whether this phenomenon is a result of plant diversity effects on host plant traits.We explored indirect effects of tree species diversity on herbivory via changes in leaf traits in a long‐term forest diversity experiment in Finland. We measured 16 leaf traits and leaf damage by four insect guilds (chewers, gall formers, leaf miners and rollers) on silver birch (Betula pendula) trees growing in one‐, two‐, three‐ and five‐species mixtures.A decline in the frequency of birch in mixed stands resulted in reduced leaf area. This, in turn, mediated the reduction in chewing damage in mixed stands. In contrast, associational resistance of birch to leaf miners was not trait‐mediated but driven directly by concurrent declines in birch frequency as tree species richness increased.Our results show that leaf trait variation across the diversity gradient might promote associational resistance, but these patterns are driven by an increase in the relative abundance of heterospecifics rather than by tree species richness per se. Therefore, accounting for concurrent changes in stand structure and key foliar traits is important for the interpretation of plant diversity effects and predictions of associational patterns.

Height-related variations of leaf traits reflect strategies for maintaining photosynthetic and hydraulic homeostasis in mature and old Pinus densiflora trees.

Because tree size and age co-vary, it is difficult to separate their effects on growth and physiological function. To infer causes for age-related height-growth decline, we compared various leaf traits between mature (ca. 100years) and old (ca. 300years) trees of Pinus densiflora, having similar heights (ca. 30m) and growing in the same stand. For many leaf traits, mature and old trees showed similar height-related trends reflecting acclimation to height-related hydraulic limitation for maintaining photosynthetic and hydraulic homeostasis. Photosynthetic capacity was constant within crowns of both age-classes, though 4.9-5.4μmol CO2 m-2s-1 lower for old than for mature trees. Biochemical acclimation of photosynthesis, allocating more nitrogen to treetop leaves, was observed only for mature trees. Leaf turgor loss point was also constant within crowns of both age-classes with no significant effect of age on leaf hydraulic traits. In mature trees, leaf capacitance increased, while bulk tissue elastic modulus decreased with height, whereas opposite height-related trends were observed for old trees. For both age-classes, leaf mass per area (LMA), transfusion-tissue area, and xylem area all increased with height, but LMA was ca. 30gm-2 greater for old than for mature trees. In old trees, mesophyll area decreased with height, suggesting anatomical acclimation to height may negatively affect photosynthetic capacity. We inferred that old trees rely more on morphological than biochemical acclimation and that such post-maturational shift in resource allocation could underlie height-growth decline of P. densiflora after reproductive maturity.

杉木人工林下原生与引入树种叶性状变异特征

PDF HTML阅读 XML下载 导出引用 引用提醒 杉木人工林下原生与引入树种叶性状变异特征 DOI: 10.5846/stxb201809202054 作者: 作者单位: 中国林业科学研究院亚热带林业研究所,中国林业科学研究院亚热带林业研究所,中国林业科学研究院亚热带林业研究所,中国林业科学研究院亚热带林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2017YFC0505500，2017YFC0505502） Variations in leaf traits of native and introduced tree species in Cunninghamia lanceolata plantations Author: Affiliation: Research Institute of Subtropical Forestry,Chinese Academy of Forestry,Research Institute of Subtropical Forestry,Chinese Academy of Forestry,Research Institute of Subtropical Forestry,Chinese Academy of Forestry,Research Institute of Subtropical Forestry,Chinese Academy of Forestry Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:叶性状在表征植物资源利用和生存策略方面具有重要作用。构建异龄复层林是改造人工纯林的有效措施，探究引入与原生树种叶性状变异有利于林下伴生树种的筛选。研究了引入乔灌木树种（如闽楠、蚊母树等13个树种）与原生乔灌木树种（苦槠、红紫珠等6个树种）的叶片形态、光合色素、碳氮磷生态化学计量和非结构性碳水化合物特征。结果表明：（1）总体上引入与原生乔木和灌木树种的叶形态性状差异较小，原生乔木的叶长和比叶面积显著小于引入树种与原生灌木。引入与原生树种间光合色素具有显著差异，引入乔木叶绿素含量显著高于原生乔木，不同功能群植物的比叶面积.叶绿素关系格局存在策略位移现象。引入树种叶碳含量显著大于原生树种，叶氮和叶磷含量显著大于原生乔木；引入树种和原生灌木的碳、氮、磷养分含量的变异系数较大；引入与原生树种叶碳氮磷生态化学计量没有一致变化规律。引入灌木叶可溶性糖含量、原生灌木淀粉含量均显著高于乔木树种，灌木的非结构性碳水化合物总量也显著高于乔木。（2）引入与原生树种叶性状呈显著协同变化趋势。所有叶性状中，比叶面积、叶绿素含量、叶氮含量、叶磷含量在乔木和灌木中均呈极显著正相关关系。主成分分析显示，引入乔木和灌木树种的叶性状接近，引入树种与原生灌木之间叶性状差异相对较小，但与原生乔木间的叶性状差异较大。总体上引入树种的叶性状与原生树种具有趋同适应特征，但不同生活型植物叶性状在林下弱光环境中仍产生一定分异，引入灌木可能比引入乔木更适应杉木林下生境。 Abstract:Leaf traits of plants play crucial roles in determining resource utilization and survival strategies. Single-layered monoculture plantations are converted to multi-layered mixed plantations is an effective measure to improve plantation quality. To study the variation of the leaf traits of introduced and native species is beneficial to select the associated tree species under forest. This study assessed the traits of leaf morphology, photosynthetic pigments, carbon, nitrogen and phosphorus ecological stoichiometry, and non-structural carbohydrates of introduced arbors and shrubs species (such as Phoebe bournei and Distylium racemosum) and native arbors and shrubs species (such as Castanopsis sclerophylla and Callicarpa rubella). The results showed that leaf length and specific leaf area of native arbors were significantly smaller than those of the introduced species and native shrubs, and the other leaf morphological traits were little difference between introduced and native species. Photosynthetic pigment content differed markedly between the introduced and native species, and the chlorophyll content of native arbors was significantly lower than that of the introduced arbors. The relationship of specific leaf area and chlorophyll varied among different functional groups. The leaf carbon content of the introduced tree species was distinctly higher than that of the native tree species, and the leaf nitrogen and phosphorus contents were significantly higher than those of the native arbors. The coefficients of variation of nutrient contents of the introduced species and native shrubs were higher than that of the native arbors. The variations in leaf carbon, nitrogen, and phosphorus eco-stoichiometry differed in the introduced and native tree species. The soluble sugar content in the introduced shrubs and the starch content in the native shrubs were markedly higher than those of arbors, and the content of the non-structural carbohydrates in the shrubs was distinctly higher than that in the arbors. The leaf traits of the introduced and native tree species showed a significant synergistic change. For the arbor and shrub species, there was a marked positive correlation among the leaf area, chlorophyll content, and leaf nitrogen and phosphorus contents. Based on principal component analysis (PCA), the leaf traits were similar between the introduced arbors and shrubs. The differences of leaf traits were relatively smaller between introduced tree species and native shrubs, while there was a large difference between introduced tree species and native arbors. The leaf traits of introduced and native tree species showed convergent adaptation. However, the leaf traits of different life forms still had some differences in the low-light environment. The introduced shrubs may be more suitable for the understory environments in Cunninghamia lanceolata. 参考文献 相似文献 引证文献

Variations of leaf construction cost and leaf traits within the species of <i>Artemisia ordosica</i> along a precipitation gradient in the Mau Us sandy land

Variations of leaf construction cost and leaf traits within the species of <i>Artemisia ordosica</i> along a precipitation gradient in the Mau Us sandy land

Grazing promotes plant functional diversity in alpine meadows on the Qinghai-Tibetan Plateau

Grazing exclosures and rotational grazing have been extensively applied to prevent grassland degradation and to restore grassland ecosystem function and services. The mechanisms associated with changes in alpine plant traits, and functional diversity under different grazing regimes have not been deeply explored. We examined the variations of plant leaf traits and functional diversity of an alpine meadow under different grazing regimes in a 3-year experiment. The results showed, after 3 years of yak grazing, that the coverage of Stipa capillata increased, whereas that of Kobresia pygmaea decreased under grazing exclosure. Stipa capillata had a lower ratio of leaf nitrogen content to phosphorus content (N:P) under grazing exclosure than under rotational grazing and continuous grazing, whereas Kobresia pygmaea showed no significant differences among grazing treatments. Among grazing regimes, the specific leaf area (SLA) of Stipa capillata was similar, whereas that of Kobresia pygmaea was higher under grazing exclosure. At the interspecific level, leaf area and weight were negatively correlated with SLA, whereas leaf carbon (C) content, leaf N content, leaf C:P and leaf N:P were negatively related to leaf P content and leaf C:N. These findings indicated that growth-defence trade-off strategies might lead to variations in plant traits and coverage. Large-leaved species, due to high maintenance costs, were less commonly distributed in the community, and they were better defended and unpalatable to yaks due to lower SLA, this formed the species coverage distribution pattern of the community. Various N and P utilisation efficiency of different species indicated diverse economic resources utilisation strategies might be due to niche differentiation in the community. Plots that had been excluded from grazing had the lowest functional richness, evenness, and divergence. Rotational and continuous grazing were equivalent in promoting alpine plant functional diversity.

Age-related changes in anatomical and morphological leaf traits of Wollemia nobilis

The results highlight significant variations of Wollemia nobilis leaf traits which reflect age-related changes of the subsequent growth units along the branches. Age-related changes appear in a gradual increase of leaf size from young leaves to old leaves. The LMA increasing from 13.75 g/cm2 in current year leaves to 24.84 g/cm2 in 7 year leaves is associated with an increment of the number of lignified elements (vascular tissues, astrosclereids), of hypodermal and epidermal-cuticle structures (cuticle, wax layer) and of oil bodies abundance, which may increase resistance to stress factors. These characteristics highlight that W. nobilis leaves can adapt to variable environmental conditions with a return rate on a larger time-scale since leaves on a branch stay alive for a long time until the branch dies.

Variation in leaf traits across a precipitation gradient in coastal sand dunes in Yucatan Peninsula

Environmental filters play an important role in plant community assembly. Evaluating spatial variation in functional traits across environmental gradients may help determine the environmental filters that play a role in community assembly and how plant communities respond to prevailing environmental conditions. In this study, we evaluated spatial variation in leaf traits (size, thickness, specific area and dry matter content) of coastal sand dune plant communities across 16 sites along a precipitation gradient in the Yucatan Peninsula. We described community-wide trait variation in terms of dispersion and dominant values across the gradient in order to answer the following questions: Which environmental filters explain variation in leaf traits? What ecological strategies, in terms of leaf economics, do these environmental filters favour? Mean specific leaf area and dispersion in leaf thickness tended to be lower in drier sites, suggesting that plants invest more biomass per leaf (a conservative strategy) and become more succulent as aridity increases. Contrary to expectation, leaf size increased with proximity to the coastline and dry matter content was significantly greater in the wettest region. Therefore, variation in these leaf traits content cannot be explained by the precipitation gradient. We have shown that predictable variation in some functional leaf traits can be found, even at small scales within the same vegetation zone in coastal sand dunes. Our study supports the notion that variation in water availability can be an important driver of functional trait distribution in the plant communities of some arid environments.

Intraspecific Trait Variation and Phenotypic Plasticity Mediate Alpine Plant Species Response to Climate Change.

In a rapidly changing climate, alpine plants may persist by adapting to new conditions. However, the rate at which the climate is changing might exceed the rate of adaptation through evolutionary processes in long-lived plants. Persistence may depend on phenotypic plasticity in morphology and physiology. Here we investigated patterns of leaf trait variation including leaf area, leaf thickness, specific leaf area, leaf dry matter content, leaf nutrients (C, N, P) and isotopes (δ13C and δ15N) across an elevation gradient on Gongga Mountain, Sichuan Province, China. We quantified inter- and intra-specific trait variation and the plasticity in leaf traits of selected species to experimental warming and cooling by using a reciprocal transplantation approach. We found substantial phenotypic plasticity in most functional traits where δ15N, leaf area, and leaf P showed greatest plasticity. These traits did not correspond with traits with the largest amount of intraspecific variation. Plasticity in leaf functional traits tended to enable plant populations to shift their trait values toward the mean values of a transplanted plants’ destination community, but only if that population started with very different trait values. These results suggest that leaf trait plasticity is an important mechanism for enabling plants to persist within communities and to better tolerate changing environmental conditions under climate change.

Contrasting leaf-trait strategies in dominant liana and tree species of Indian tropical dry evergreen forest

Recent studies have revealed convergence in the variation of leaf traits across various plant life-forms on a global scale. This study aims to analyze and compare the leaf-trait strategies of dominant liana and tree species in Indian tropical dry evergreen forest (TDEF). The study also checks whether these life-forms differ in their resource acquisition strategies explained by the variance in their leaf functional traits. The present study was carried out in a permanent plot established in a TDEF site on the Coromandel Coast of India. We selected ten dominant species of lianas and trees to analyze and compare their leaf-trait strategies. For each species, we collected 30 healthy sun leaves from at least eight individuals. The collected leaf samples were analyzed for various leaf functional traits using standard protocol. Lianas had higher specific leaf area and mass-based leaf nitrogen than the trees. Trees had higher leaf lamina area, leaf thickness, leaf mass per area, leaf tissue density and C:N than the lianas. Lianas and trees in the studied site differed significantly in six out of seven leaf-functional traits analyzed. The observed leaf trait strategies of lianas in TDEF could offer competitive advantage for them over trees.

Leaf to canopy upscaling approach affects the estimation of canopy traits

In remote sensing applications, leaf traits are often upscaled to canopy level using sunlit leaf samples collected from the upper canopy. The implicit assumption is that the top of canopy foliage material dominates canopy reflectance and the variability in leaf traits across the canopy is very small. However, the effect of different approaches of upscaling leaf traits to canopy level on model performance and estimation accuracy remains poorly understood. This is especially important in short or sparse canopies where foliage material from the lower canopy potentially contributes to the canopy reflectance. The principal aim of this study is to examine the effect of different approaches when upscaling leaf traits to canopy level on model performance and estimation accuracy using spectral measurements (in-situ canopy hyperspectral and simulated Sentinel-2 data) in short woody vegetation. To achieve this, we measured foliar nitrogen (N), leaf mass per area (LMA), foliar chlorophyll and carbon together with leaf area index (LAI) at three vertical canopy layers (lower, middle and upper) along the plant stem in a controlled laboratory environment. We then upscaled the leaf traits to canopy level by multiplying leaf traits by LAI based on different combinations of the three canopy layers. Concurrently, in-situ canopy reflectance was measured using an ASD FieldSpec-3 Pro FR spectrometer, and the canopy traits were related to in-situ spectral measurements using partial least square regression (PLSR). The PLSR models were cross-validated based on repeated k-fold, and the normalized root mean square errors (nRMSEcv) obtained from each upscaling approach were compared using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test. Results of the study showed that leaf-to-canopy upscaling approaches that consider the contribution of leaf traits from the exposed upper canopy layer together with the shaded middle canopy layer yield significantly (p < 0.05) lower error (nRMSEcv < 0.2 for canopy N, LMA and carbon) as well as high explained variance (R2 > 0.71) for both in-situ hyperspectral and simulated Sentinel-2 data. The widely-used upscaling approach that considers only leaf traits from the upper illuminated canopy layer yielded a relatively high error (nRMSEcv>0.2) and lower explained variance (R2 < 0.71) for canopy N, LMA and carbon. In contrast, canopy chlorophyll upscaled based on leaf samples collected from the upper canopy and total canopy LAI exhibited a more accurate relationship with spectral measurements compared with other upscaling approaches. Results of this study demonstrate that leaf to canopy upscaling approaches have a profound effect on canopy traits estimation for both in-situ hyperspectral measurements and simulated Sentinel-2 data in short woody vegetation. These findings have implications for field sampling protocols of leaf traits measurement as well as upscaling leaf traits to canopy level especially in short and less foliated vegetation where leaves from the lower canopy contribute to the canopy reflectance.

Experimental Study of Environmental Effects: Leaf Traits of JuvenileFagus sylvatica,Acer pseudoplatanus, andCarpinus betulusAre Comparable to Leaves of Mature Trees in Upper Canopies

Morphological and functional leaf traits like leaf toughness and nutrient content are essentially influenced by the environment, especially through light and climatic conditions. Varying light conditions have been identified as a significant predictor for the variation of many leaf traits. However, the leaf acclimation to light is suggested to be of secondary importance. The aim of the experimental study was to analyse environmental effects (microclimate and soil moisture), which are present in upper canopies of forest stands, on leaf traits of juvenileFagus sylvaticaL. (European beech; Fagaceae),Acer pseudoplatanusL. (sycamore maple; Sapindaceae), andCarpinus betulusL. (hornbeam; Betulaceae). The experimental design managed to imitate two distinct microclimates causing different temperature and air humidity conditions. Furthermore, the irrigation treatment with different levels of applied water caused distinct soil moisture conditions in the trial pots. As a result of the treatments, leaves ofC. betulusshowed a tendency of decreased specific leaf area (SLA) caused by the treatment with warmer and drier microclimate. The environmental effect on SLA was even stronger with lower soil moisture conditions. Chlorophyll content showed lower values in treatments with higher soil moisture conditions in both greenhouses forF. sylvaticaandA. pseudoplatanus. The trends are in accordance with combined effects of temperature, air humidity, and soil moisture on SLA, and increased leaf chlorophyll content caused by slight drought stress. Plants in the greenhouses were exposed to full sunlight indicating a microclimatic environment comparable to upper canopies in forest stands. The comparable SLA and chlorophyll content between leaves of matureF. sylvaticatrees in upper canopies and juvenile trees of the greenhouses suggest similar environmental conditions instead of ontogenetic effects that are responsible for the formation of leaf trait characteristics.

Quantifying leaf-trait covariation and its controls across climates and biomes.

Plant functional ecology requires the quantification of trait variation and its controls. Field measurements on 483 species at 48 sites across China were used to analyse variation in leaf traits, and assess their predictability. Principal components analysis (PCA) was used to characterize trait variation, redundancy analysis (RDA) to reveal climate effects, and RDA with variance partitioning to estimate separate and overlapping effects of site, climate, life-form and family membership. Four orthogonal dimensions of total trait variation were identified: leaf area (LA), internal-to-ambient CO2 ratio (χ), leaf economics spectrum traits (specific leaf area (SLA) versus leaf dry matter content (LDMC) and nitrogen per area (Narea )), and photosynthetic capacities (Vcmax , Jmax at 25°C). LA and χ covaried with moisture index. Site, climate, life form and family together explained 70% of trait variance. Families accounted for 17%, and climate and families together 29%. LDMC and SLA showed the largest family effects. Independent life-form effects were small. Climate influences trait variation in part by selection for different life forms and families. Trait values derived from climate data via RDA showed substantial predictive power for trait values in the available global data sets. Systematic trait data collection across all climates and biomes is still necessary.

Altitudinal Patterns of Leaf Traits and Leaf Allometry in Bamboo Pleioblastus amarus.

Awareness of local-scale variation in leaf traits for a single species and the relationships between these traits and their dependence on altitude might be essential for extrapolating ecophysiological processes from the leaf to the ecosystem level. While altitudinal patterns of leaf traits have been extensively studied in a number of species, little is known about such patterns in bamboos. We analyzed leaf functional traits and leaf allometric relationships of Pleioblastus amarus at three different altitudes (200, 400, and 800 m). With increasing altitude, most functional traits, including leaf length, width, perimeter, area, dry weight, and water content, decreased significantly, while the leaf length:width ratio exhibited a marked increase, resulting in a tendency toward narrow leaves. Specific leaf area first increased, and then decreased, while the change in leaf dry matter content showed the opposite trend. Leaf area was positively correlated with leaf length, leaf width and leaf perimeter, but negatively correlated with the leaf length:width ratio. With increasing altitude, the slopes of these relationships for leaf area first increased, and then decreased. Leaf biomass was positively correlated with leaf length, width, perimeter, and area, with the slopes of the relationships being the same at all altitudes. Thus, the leaves of this bamboo species at middle altitude have the highest specific leaf area and lowest leaf dry matter content. Our findings suggest that this bamboo species has a big potential of growth and morphological plasticity.