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The leaf pigment complex traits of 44 wetland plant species from the Middle Urals (Russia) were studied to analyze their diversity in relation to taxonomy and life forms. The chlorophyll content per dry weight (ChlDW) and leaf area (ChlArea), the ratio of chlorophylls a and b, and CO2 uptake rates (ADW) were determined. ChlDW varied by 10-fold from 2.20 to 21.9 mg g−1 among the wetland plant species. The influence of taxonomy at the level of classes on the variation of the pigment complex traits was revealed. Dicots had greater ChlDW and had a greater proportion of chlorophylls in the light-harvesting complex (ChlLHC) than monocots. In dicots, ChlLHC was positively correlated with leaf area ratio (r = 0.63, p < 0.01), and the effect of life forms on the content and ratio of pigments was determined. In monocots, chlorophyll content was positively correlated with ADW (r = 0.75, p < 0.001) and plant height (r = 0.66, p < 0.001). In monocots, the effect of families on the pigment content was observed. The lack of differences in ChlArea between the different systematic groups and life forms indicates a similar ability of the leaf area unit to absorb a solar energy.

Invasive alien species (IAS) are a problem, especially in drought-prone environments such as the Mediterranean Basin where the exacerbation of the already severe conditions could constrain the native species acclimatation degree, creating new opportunities for IAS. Climate change may drive IAS expansions, even if different IAS can vary in their acclimatation response. Thus, it is important to obtain a broader insight of how the different IAS face abiotic stress. This research aimed to compare the effect of the imposed water stress on physiological and morphological leaf traits of Ailanthus altissima (AA), Robinia pseudoacacia (RP), and Phytolacca americana (PA), which are widely spread IAS in the Mediterranean Basin. Our results showed a species-dependent effect of the water stress at a physiological and morphological level, as well as an interaction between species and stress duration. Despite a common strategy characterized by low stomatal control of the photosynthesis, AA, PA, and RP differ in their sensitivity to water stress. In particular, even if AA was characterized by a more water-spending strategy, it was more resistant to water stress than PA and RP. In this view, the key factor was its plasticity to increase leaf mass per area (LMA) in response to water stress.

Lettuce (Lactuca sativa L.) is a winter-spring leafy vegetable, but the high demand for fresh products available year-round requires off-season production. However, the warm climate of the Mediterranean areas can impair the summer production of lettuce, thus requiring the adoption of genotypes tolerant to high irradiance as well as useful agronomic strategies like shading net installations. The aim of our research was to assess the leaf morpho-physiological and anatomical changes, in addition to productive responses, of four lettuce cultivars (‘Ballerina’, ‘Maravilla De Verano Canasta’, ‘Opalix’, and ‘Integral’) grown under shading and non-shading conditions to unveil the adaptive mechanisms of this crop in response to sub-optimal microclimate (high irradiance and temperature) in a protected environment. Growth and yield parameters, leaf gas exchanges, chlorophyll fluorescence and morpho-anatomical leaf traits (i.e., leaf mass area, stomatal density and epidermal cell density) were determined. Under shading conditions, the fresh yields of the cultivars ‘Ballerina’, ‘Opalix’ (‘Oak leaf’) and ‘Integral’ (‘Romaine’) increased by 16.0%, 26.9% and 13.2% respectively, compared to non-shading conditions while both abaxial and adaxial stomatal density decreased. In contrast, ‘Canasta’ under non-shading conditions increased fresh yield, dry biomass and instantaneous water use efficiency by 9.6%, 18.0% and 15.7%, respectively, while reduced abaxial stomatal density by 30.4%, compared to shading conditions. Regardless of cultivar, the unshaded treatment increased the leaf mass area by 19.5%. Even though high light intensity and high temperature are critical limiting factors for summer lettuce cultivation in a protected environment, ‘Canasta’ showed the most effective adaptive mechanisms and had the best production performance under sub-optimal microclimatic conditions. However, greenhouse coverage with a white shading net (49% screening) proved to be a suitable agricultural practice that ensured an adequate microclimate for the off-season growth of more sensitive cultivars ‘Ballerina’, ‘Oak leaf’ and ‘Romaine’.

Large-scale high-resolution satellite observations of plant functional diversity patterns will greatly benefit our ability to study ecosystem functioning. Here, we demonstrate a potentially scalable approach that uses aggregate plant traits estimated from radiative transfer model (RTM) inversion of Sentinel-2 satellite images to calculate community patterns of plant functional diversity. Trait retrieval relied on simulations and Look-up Tables (LUTs) generated by a RTM rather than heavily depending on a priori field data and data-driven statistical learning. This independence from in-situ training data benefits its scalability as relevant field data remains scarce and difficult to acquire. We ran a total of three different inversion algorithms that are representative of commonly applied approaches and we used two different metrics to calculate functional diversity. In tandem with Sentinel-2 image-based estimation of plant traits, we measured Leaf Area Index (LAI), leaf Chlorophyll content (CAB), and Leaf Mass per Area (LMA) in-situ in a (semi-)natural heterogeneous landscape (Montesinho region) located in northern Portugal. Sampling plots were scaled and georeferenced to match the satellite observed pixels and thereby allowed for a direct one-to-one posterior ground truth validation of individual traits and functional diversity. Across approaches, we observe a reasonable correspondence between the satellite-based retrievals and the insitu observations in terms of the relative distribution of individual trait means and plant functional diversity across locations despite the heterogeneity of the landscape and canopies. The functional diversity estimates, based on a combination of canopy and leaf traits, were robust against estimation biases in trait means. Particularly, the convex hull volume estimate of functional diversity showed strong concordance with in-situ observations across all three inversion methods (Spearman's rho: 0.67-0.80). The remotely sensed estimates of functional diversity also related to in-situ taxonomic diversity (Spearman's rho: 0.55-0.63). Our work highlights the potential and challenges of RTM-based functional diversity metrics to study spatial community-level ecological patterns using currently operational and publicly available Sentinel-2 imagery. While further validation and assessment across different ecosystems and larger datasets are needed, the study contributes towards a further maturation of scalable, spatially, and temporally explicit methods for functional diversity assessments from space. The authors would like to acknowledge Christian Rossi, Prof. Geof-frey M. Henebry, and the anonymous reviewers for their valuable comments and suggestions that greatly improved the manuscript. This work was supported financially by the Ecology Fund of the RoyalNetherlands Academy of Arts and Sciences (‘KNAW Fonds Ecologie’; KNAWWF/807/19011). We thank Altino Geraldes, Joao Carlos Aze-vedo, and the local farmers and foresters in the Montesinho-Nogueira Natura 2000 site for their help and collaboration. We thank Emilie Didaskalou for her lab assistance. J.-B. F ́eret acknowledges financial support from Agence Nationale de la Recherche (BioCop project—ANR- 17-32CE-0001).

Plant functional traits are highly plastic to changes in climatic factors and nutrient availability. However, the intraspecific plant response to abiotic factors and the overall effect on tree growth and productivity is still under debate. We studied forest productivity for 30 Quercus ilex subsp. ballota forests in Spain along a broad climatic gradient of aridity (mean annual precipitation from 321 to 858 mm). We used linear mixed models to quantify the effect of climatic and edaphic (soil nutrients, topography, and texture) factors on tree functional traits (leaf and branch traits), and subsequently, the effect of such functional traits and abiotic factors on the relative growth rate (RGR) of adult trees. We used piecewise structural equation models (SEMs) to determine the causal effect of intrinsic and extrinsic factors on forest productivity. Our results showed that tree functional traits were mainly explained by climatic and edaphic factors. Functional traits and tree biomass explained forest biomass and RGR, respectively, which ultimately explained forest productivity. In conclusion, intraspecific variability of functional traits has a significant effect on plant biomass and growth, which ultimately may explain forest productivity in Quercus ilex forests., Fondo Europeo de Desarrollo Regional-FEDER, Junta de Andalucía, Ministerio de Educación y Ciencia, Gobierno de España

Plant and community traits provide valuable insights in ecosystem functioning. Yet, such traits are costly to sample. Existing trait data bases give access to species-specific traits and help to reduce the sampling effort and costs. However, many traits show a high intra-specific plasticity due to the variability of environmental conditions, which is not fully accounted for in the data bases. As an alternative approach, remote sensing is able to retrieve some traits from the spectral reflectance signal of the canopy. Here we test whether remotely sensed traits provide the level of detail to trace the trait plasticity in response to changing environmental conditions. For this proof of concept study, we selected the example of leaf mass per area (LMA), a key trait for ecosystem functioning and good negative correlate of potential growth rate, in our study site Las Tablas de Daimiel National Park (Spain). This wetland was affected by a long-term drought, which introduced a pronounced trait plasticity as part of the adaptation mechanisms of the vegetation to reduced water availability as well as a decrease in photosynthetic activity. Imaging spectroscopy (HyMap) data of the wetland at peak drought intensity were acquired in 2009 simultaneous to a field campaign. We applied an inversion of the PROSAIL radiative transfer model on these data to map the LMA distribution across the wetland. Further, we quantified trends in photosynthetic activity and changing species composition across the wetland by analyzing time series of the normalized difference vegetation index (NDVI) as calculated for multispectral remote sensing data. The retrieved LMA values were analyzed within and between stands of different species and communities along a gradient of changing photosynthetic activity and species composition. Results show that LMA values retrieved for stands of species with high photosynthetic activity at peak drought intensity closely meet the values reported in data bases. The observed intra-specific LMA variability is in line with the expected plasticity of this trait along a moisture gradient that is reflected in a change in photosynthetic activity and species composition. We thus conclude that LMA values retrieved from imaging spectroscopy data provide sufficient detail to trace the response of wetland vegetation to long-term drought stress., Funding for this study was granted by the German Ministry of Economics and Technology (BMWI) within the framework of the project of the 2009 EnMAP preparation campaign, the DECAMERON project 1/2008 of the Agency for National Parks of the Spanish Ministry of Agriculture, Food and Environment, and by the German Research Foundation (DFG grant FE1331/2-1).

Question Understanding how the relative importance of different community assembly processes changes during secondary succession of diverse systems remains elusive. Functional and phylogenetic approaches that place species along continuous axes of niche differentiation and evolutionary relatedness, however, are deepening our understanding of the mechanisms that drive successional dynamics. We ask whether successional shifts in the functional and phylogenetic composition of post-agricultural tropical forests provide evidence for niche partitioning or competitive dominance hierarchies as drivers of successional change. Location Subtropical wet forests, Puerto Rico. Methods We combined data on four functional traits [leaf dry mass per area (LMA), wood density (WD), maximum height (Hmax), seed dry mass] and a well-resolved molecular phylogeny to characterize taxonomic, functional and phylogenetic composition of sapling and adult tree communities along a regionally replicated chronosequence. We used a null model approach to assess how functional and phylogenetic diversity change with forest age. Results Corresponding increases of community-weighted mean LMA, Hmax and seed mass with forest age reflected a shift in dominance of species with acquisitive resource-use strategies and small seeds towards species with more conservative resource use and larger seeds. A negative relationship between forest age and local diversity of Hmax and seed mass suggested increased importance of competitive hierarchies for light capture and shade-tolerant regeneration in older forests. In contrast, the colonization of palms in older forest plots led to a positive relationship between forest age and local phylogenetic diversity, suggesting functional convergence of distantly related lineages on traits that confer competitive dominance under low resource conditions. Conclusions We linked both functional and phylogenetic dimensions of community diversity with successional trajectories of post-agricultural tropical forests. Contrasting patterns of these dimensions of diversity shed light on the underlying community assembly processes. We argue that integrating traits and phylogeny with specific hypotheses about physiological and historical mechanisms is essential for advancing our understanding of the drivers of community change during succession.

14 páginas.-- 4 figuras.-- 1 tablas.-- 38 referencias.-- Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11104-017-3433-4), Background and aims: Root traits play a critical role in plant resource-use strategies and ecosystem functioning, but there is great controversy regarding their identity and functionality in different dimensions of belowground functional variation. Here, we explored the level of covariation among a suite of key root traits (i.e. specific root length, root dry matter content, diameter and density) as well as between them and two aboveground traits related with plant function (leaf nutrient concentration and specific leaf area). We also evaluated whether these patterns of trait covariation were consistent at different spatial scales and organisational levels. Methods: We collected fine root (< 2 mm) samples of 534 individuals (of 80 woody species) along a wide regional range of environmental conditions in southern Spain. Results: In general, strong correlations among most of the root morphological traits were found, supporting the existence of a ‘root economics spectrum’, as well as between root traits and the aboveground traits. However, root diameter was not completely aligned along this ecological axis, supporting the idea of a multidimensional spectrum of root traits. The main syndrome of root trait covariation was consistent at the different spatial scales and organisational levels. Soil nutrients and water availability were the main drivers of root trait variation. Conclusions: Our results indicate that root trait variation is primarily aligned along a leading dimension related to resource economics. However, the distinct pattern of root diameter may indicate a multidimensionality of belowground traits that needs to be explored in greater depth., This study was funded by the Spanish MEC coordinated project DIVERBOS (CGL2011-30285-C02- 01 and C02-02), ECO-MEDIT (CGL2014-53236-R), RESTECO (CGL2014-52858-R), ECOMETAS (CGL2014-53840-REDT), the Life + Biodehesa Project (11/BIO/ES/000726) and European FEDER funds.

Summary Leaf hydraulic capacity and vulnerability to drought stress are key determinants of plant competitive ability and productivity. Yet, it is not clear how these traits correlate to climatic variables across biomes and whether a trade-off exists between them. We collected leaf hydraulics data for 130 woody angiosperms from selected published articles. Species-specific values of leaf hydraulic capacity on a leaf area (Kleaf_area) and dry mass (Kleaf_mass) basis, leaf water potential inducing 50% loss of Kleaf (P50), as well as climatic variables (mean annual temperature, MAT and precipitation, MAP) for study sites were collected. Species were classified as belonging to three major biomes, that is dry sclerophyllous forests (DSF), temperate forests (TMF) and tropical forests (TRF). Significant differences were observed between biomes, with DSF species displaying the lowest hydraulic efficiency (low Kleaf) and the highest resistance to drought stress (low P50). P50 was correlated with both MAP and MAT, with species from low precipitation habitats having the lowest P50 values. Both Kleaf_area and Kleaf_mass were positively correlated with MAP and MAT. Leaf gas exchange rates were positively correlated with both Kleaf_area and Kleaf_mass. Although no correlation was found between P50 and Kleaf_area, a weak trade-off between leaf hydraulic safety and capacity emerged when P50 was plotted versus Kleaf_mass. Leaf hydraulics emerge as an important functional trait underlying plant adaptation to different habitats and contributing to shape vegetation features in different biomes.

Determining how the relative strength of community assembly processes varies along resource gradients is critical for understanding community responses to environmental change. A key challenge for addressing this issue at regional scales is that environmental gradients typically encompass multiple coupled resource gradients (e.g. water, light, soils), which can complicate hypotheses about the drivers of community variation. We used data on functional traits and phylogenetic relatedness to infer assembly processes of tree communities across regional environmental gradients in Puerto Rico. We censused trees in 24, 0.25-ha mature plots located along a precipitation gradient and on soils derived from two parent materials (limestone and volcanic). In each plot, we quantified abiotic conditions in terms of mean annual precipitation, canopy openness, and soil nutrients. We used three functional traits with relevance for drought tolerance and resource acquisition strategies (wood density [WD], leaf mass per area [LMA], and maximum height [Hmax]), and a molecular phylogeny, to characterize tree community composition in terms of (i) community-weighted mean trait values (i.e., plot average trait values, weighted by relative basal area), (ii) functional diversity, and (iii) phylogenetic diversity. Mean annual precipitation was negatively correlated with understory light availability (for plots on both soil types), and soil fertility (among plots on limestone soils). Soil fertility varied substantially between plots on each parent material, and was generally higher among plots on limestone-derived soils. Among the limestone soil plots, which occur on the drier half of the precipitation gradient, increasing mean annual precipitation was associated with lower community-weighted mean WD and LMA, and taller Hmax. Additionally, functional diversity (of WD and Hmax) and phylogenetic diversity increased with precipitation among limestone soil plots, suggesting an important role for abiotic filtering in driving functional and phylogenetic convergence in arid conditions. In contrast, we did not find significant relationships between environmental conditions and community-weighted mean traits or diversity metrics among plots on volcanic-derived soils, which occur along the wetter half of the precipitation gradient. Together, our results suggest that drought tolerance is the dominant assembly mechanism controlling tree composition in dry forests. In wetter forests, functional diversity appears to be maintained by a combination of hierarchical competition for light and niche partitioning. Overall, our results exhibit geographic variation in the mechanisms governing composition of tropical forests across regional environmental gradients, and highlight the importance of considering complex environmental gradients at large spatial scales.

El bosque templado lluvioso (sur de Chile) está conformado por tipos forestales que difieren en composición y dominancia de las especies. Estas diferencias deberían determinar cambios en componentes de la diversidad que presentan correlación entre ellos. Este estudio buscó determinar si existe un vínculo entre la riqueza de especies leñosas (S) y la diversidad funcional de sus atributos foliares, en dos ensambles forestales que difieren en composición florística: tipos forestales Valdiviano y Coihue. Se postuló que: i) existe una relación global positiva entre la diversidad funcional y la S; ii) y que como los ensambles difieren en composición, la magnitud de la relación entre diversidad funcional y S diferirá entre los dos tipos forestales. Se describió la diversidad funcional a partir de los índices media-comunitaria-ponderada (CWM) y divergencia funcional (FDvg), de los atributos masa foliar específica (LMA) y contenido relativo de clorofila (Chl r). Estos atributos fueron medidos, junto con la abundancia, en todas las especies leñosas presentes en los dos ensambles (10 parcelas de 225 m² por ensamble). Se encontró una relación global positiva sólo entre FDvg-LMA y S, y el mismo patrón emerge cuando se evalúa esta relación dentro de cada tipo forestal, independiente de que estas comunidades presenten diferentes especies dominantes, o que además difieran en el valor promedio de la FDvg-LMA. Sin embargo, al comparar la magnitud de esta relación entre los dos ensambles no se encontraron diferencias significativas. La riqueza de especies leñosas puede ser un buen predictor de la diversidad funcional en las comunidades forestales del bosque templado lluvioso, dependiendo del atributo funcional utilizado para inferir dicho componente de la diversidad. A partir de esto, es posible inferir que cuando hay mayor número de especies leñosas en una comunidad del bosque estudiado, también habría una mayor probabilidad de encontrar que las especies difieran en atributos funcionales como LMA.

Made available in DSpace on 2018-11-26T16:16:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Scleromorphic leaf structures are associated with plants growing under drought-prone conditions, high irradiances, and nutrient-poor soils. Sclerophylly can also be a valuable deterrent against herbivores. However, comprehensive studies of leaf anatomical traits encompassing different growth forms are lacking. The savannas of central Brazil (Cerrado) are characterized by high species diversity and a variety of growth forms. We performed a field study to characterize leaf anatomical traits and leaf mass per area (LMA) in 57 co-occurring Cerrado species of distinct plant families (located at different positions in the angiosperm phylogeny) and categorized according to the following growth forms: trees, palms, shrubs, subshrubs, vines, grasses and herbs. Plant growth form and leaf structure were interrelated. Four groups with distinct leaf anatomical syndromes were identified by NMDS analysis: grasses, palms, herbaceous (herbs, vines, and most subshrubs), and woody (trees and shrubs) plants. Trees and shrubs had scleromorphic dorsiventral leaves, with high tissue thickness and LMA. Herbaceous plants had thin, mesomorphic leaves. While most herbaceous plants had dorsiventral type of mesophyll, grasses and palms had homogenous mesophyll with sclerenchymatous bundle sheath extensions. Palms differed from grasses by having thicker leaves and sclerenchymatous hypodermis. In conclusion, Neotropical savannas cannot be exclusively described as scleromorphic vegetation. Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Biol, BR-14884900 Jaboticabal, SP, Brazil Univ Estadual Paulista, Fac Ciecias & Letras, Dept Ciencias Biol, BR-19806900 Assis, SP, Brazil Univ Brasilia, Inst Ciencias Biol, Dept Bot, BR-70904970 Brasilia, DF, Brazil Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Biol, BR-14884900 Jaboticabal, SP, Brazil Univ Estadual Paulista, Fac Ciecias & Letras, Dept Ciencias Biol, BR-19806900 Assis, SP, Brazil CNPq: 141624/2009-4 CNPq: 484545/2012-4 CNPq: 303637/2011-0 FAPESP: 2011/23112-3 FAPESP: 2013/18049-6

Leaf hydraulic conductance (K(leaf) ) and vulnerability constrain plant productivity, but no clear trade-off between these fundamental functional traits has emerged in previous studies. We measured K(leaf) on a leaf area (K(leaf_area)) and mass basis (K(leaf_mass)) in six woody angiosperms, and compared these values with species' distribution and leaf tolerance to dehydration in terms of P(50), that is, the leaf water potential inducing 50% loss of K(leaf) . We also measured several morphological and anatomical traits associated with carbon investment in leaf construction and water transport efficiency. Clear relationships emerged between K(leaf_mass), P(50), and leaf mass per unit area (LMA), suggesting that increased tolerance to hydraulic dysfunction implies increased carbon costs for leaf construction and water use. Low P(50) values were associated with narrower and denser vein conduits, increased thickness of conduit walls, and increased vein density. This, in turn, was associated with reduced leaf surface area. Leaf P(50) was closely associated with plants' distribution over a narrow geographical range, suggesting that this parameter contributes to shaping vegetation features. Our data also highlight the carbon costs likely to be associated with increased leaf tolerance to hydraulic dysfunction, which confers on some species the ability to thrive under reduced water availability but decreases their competitiveness in high-resource habitats.

Morphological, anatomical and physiological summer and winter leaf traits of Cistus incanus subsp. incanus, C. salvifolius and C. monspeliensis growing at the Botanical garden of Rome were analyzed. With regard to differences between summer and winter leaves of the considered species, leaf thickness (L) was 21% higher in summer than in winter leaves (mean of the considered species) and this increase was mostly the result of the increased palisade parenchyma thickness over the spongy parenchyma one (24 and 16% higher in summer than in winter leaves, respectively). Leaf mass area (LMA) and leaf tissue density (LTD) were 38% and 17% higher in summer than in winter leaves, respectively (mean of the considered species). The photosynthetic rate (PN), stomatal conductance (gs) and chlorophyll content (Chl) of summer leaves were 54%, 17% and 14% lower, respectively, than in winter leaves. C. monspeliensis summer leaves had the highest LMA, LTD, adaxial cuticle thickness (14.6 ± 1.8 mg cm−2, 1091 ± 94 mg cm−3, and 5.8 ± 1.7 μm, respectively) and the lowest mesophyll intercellular spaces (fias 38 ± 3%). Moreover, C. monspeliensis had the highest PN in summer (2.6 ± 0.1 μmol m−2 s−1) and C. incanus the highest PN and WUE (84% and 59% higher than the other species) in the favorable period, associated to a higher fias (42 ± 2%). C. salvifolius had the highest PN (54% higher than the other species) in winter. The plasticity index could allow a better interpretation of the habitat preference of the considered species. The physiological plasticity (PIp = 0.39, mean value of the considered species) was higher than the morphological (PIm = 0.22, mean value) and anatomical (PIa = 0.13, mean value) plasticity. Moreover, among the considered species, C. salvifolius and C. incanus are characterized by a larger PIa (0.14, mean value) which seems to be correlated with their wider ecological distribution and the more favorable conditions of the environments where they naturally occur. The highest PIm (0.29) of C. monspeliensis indicates that it can play a high adaptive role in highly stressed environments, like fire degraded Mediterranean areas in which it occurs.

Relationships between leaf traits and the gap dependence for regeneration, and ontogenetic changes therein, were investigated in juvenile and adult tropical rainforest tree species. The juveniles of the 17 species included in the study were grown in high light, similar to the exposed crowns of the adult trees. The traits were structural, biomechanical, chemical and photosynthetic. With increasing species gap dependence, leaf mass per area (LMA) decreased only slightly in juveniles and remained constant in adults, whereas punch strength together with tissue density decreased, and photosynthetic capacity and chlorophyll increased. Contrary to what has been mostly found in evergreen tropical rainforest, the trade-off between investment in longevity and in productivity was evident at an essentially constant LMA. Of the traits pertaining to the chloroplast level, photosynthetic capacity per unit chlorophyll increased with gap dependence, but the chlorophyll a/b ratio showed no relationship. Adults had a twofold higher LMA, but leaf strength was on average only about 50% larger. Leaf tissue density, and chlorophyll and leaf N per area were also higher, whereas chlorophyll and leaf N per unit dry mass were lower. Ranking of the species, relationships between traits and with the gap dependence of the species were similar for juveniles and adults. However, the magnitudes of most ontogenetic changes were not clearly related to a species’ gap dependence. The adaptive value of the leaf traits for juveniles and adults is discussed. Electronic supplementary material The online version of this article (doi:10.1007/s00442-011-2175-x) contains supplementary material, which is available to authorized users.

International audience; The potential of a chlorophyll meter (CCM-200, Opti-Sciences, Tyngsboro, MA, USA) for the estimation of total leaf chlorophyll contents was evaluated in leaves of different developmental stages for Quercus pyrenaica Willd., Q. faginea Lam., Q. suber L. and Q. ilex L. subsp. ballota (Desf.) Samp.* For all species and leaf stages, a strong non-linear relationship (P < 0.0001) was found between the chlorophyll content index (CCI) and leaf chlorophyll content per unit area. In all species, the slope of the CCI-chlorophyll content relationship varied during leaf development, suggesting that caution should be exercised when using the CCM-200, since the interpretation of CCI readings should be limited to samples of similar leaf age. Also, the data indicate that the models should also be species-specific, owing to differences in the intercept and/or slope of the equations.* The addition of fresh LMA as a complementary parameter improved the accuracy of chlorophyll estimation in non-species-specific equations to a considerable extent when leaf samples of similar development were considered.* After due consideration, it may be concluded that the CCM-200 chlorophyll meter is a reliable method for acquiring an estimation of chlorophyll contents in Mediterranean Quercus species, with potential use as an effective tool in forest management.; Le potentiel d'un chlorophyllomètre (CCM-200, Opti-Sciences, Tyngsboro, MA, USA) pour l'estimation du contenu total des feuilles en chlorophylle a été évalué dans des feuilles à différents stades de développement chez Quercus pyrenaica Willd., Q. faginea Lamb. Q. suber L. et Q. ilex L. subsp. ballota (Desf.) Samp.* Pour toutes les espèces et les feuilles à différents stades, une forte relation non linéaire (P < 0,0001) a été trouvée entre l'index de teneur en chlorophylle (CCI) et la teneur en chlorophylle des feuilles par unité de surface. Chez toutes les espèces, la pente de la relation CCI-teneur en chlorophylle a varié avec le développement de la feuille, ce qui suggère que la prudence est de mise lors de l'utilisation du CCM-200,puisque l'interprétation des indications du CCI devraient être limitées à des échantillons de feuilles d'âge similaire. Aussi, les données indiquent que les modèles devraient également être spécifiques à l'espèce, en raison des différences dans l'interception et/ou la pente des équations.* L'ajout de nouvelles LMA en tant que paramètre complémentaire a amélioré la précision de l'estimation de la chlorophylle dans les équations non spécifiques de l'espèce, et ceci dans une large mesure lorsque des échantillons de feuilles de développement similaires ont été examinés.* Après mûre réflexion, il peut être conclu que le chlorophyllomètre CCM-200 est une méthode fiable pour l'acquisition d'une estimation de la teneur en chlorophylle des espèces méditerranéennes de Quercus, avec la possibilité de l'utiliser comme un outil efficace pour la gestion des forêts.

As trees grow taller, the energetic cost of moving water to the leaves becomes higher and could begin to limit carbon gain and subsequent growth. The hydraulic limitation hypothesis states that as trees grow taller, the path length and therefore frictional resistance of water flow increases, leading to stomatal closure, reduced photosynthesis and decreased height growth in tall trees. Although this hypothesis is supported by the physical laws governing water movement in trees, its validation has been complicated by the complex structure of most tree species. Therefore, this study tested the hydraulic limitation hypothesis in Washingtonia robusta (H. Wendl.), a palm that, while growing to tall heights, is still structurally simple enough to act as a model organism for testing. There were no discernable relationships between tree height and stomatal conductance, stomatal densities, guard cell lengths, leaf dry mass per unit area (LMA) or sap flux, suggesting that these key aspects of hydraulic limitation are not reduced in taller palms. Taller palms did, however, have higher maximum daily photosynthetic assimilation rates, lower minimum leaf water potentials that occurred earlier in the day and fewer, smaller leaves than did shorter palms. Leaf epidermal cells were also smaller in taller palms compared with shorter ones. These findings are consistent with hydraulic compensation in that tall palms may be overcoming the increased path length resistance through smaller, more efficient leaves and lower leaf water potentials than shorter palms.

The main objective of this paper was to look into the morphological differentiation patterns and phenotypic plasticity in four populations of Argania spinosa with environmentally contrasted conditions. Mean response, magnitude and pattern of morphological intra- and inter-population plasticity indexes were measured and analyzed in order to identify which characters contribute the most to the acclimation of this species. Populations growing in the ecological optimum of the species presented the lowest plasticity, while those growing in the most stressed habitats showed an increased morphological variability. The study of four populations showed that human pressure seems to play an important function in the regulation of morphological characters. However, climatic conditions seem to play a significant role in the increase of morphological plasticity.