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Background and Aims The existence of sclerophyllous plants has been considered an adaptive strategy against different environmental stresses. Given that it literally means 'hard-leaved', it is essential to quantify the leaf mechanical properties to understand sclerophylly. However, the relative importance of each leaf trait for mechanical properties is not yet well established. Methods Genus Quercus is an excellent system to shed light on this because it minimizes phylogenetic variation while having a wide variation in sclerophylly. We measured leaf anatomical traits and cell wall composition, analysing their relationship with leaf mass per area and leaf mechanical properties in a set of 25 oak species. Key Results The upper epidermis outer wall makes a strong and direct contribution to the leaf mechanical strength. Moreover, cellulose plays a crucial role in increasing leaf strength and toughness. The principal component analysis plot based on leaf trait values clearly separates Quercus species into two groups corresponding to evergreen and deciduous species. Conclusions Sclerophyllous Quercus species are tougher and stronger owing to their thicker epidermis outer wall and/or higher cellulose concentration. Furthermore, section Ilex species share common traits, although they occupy different climates. In addition, evergreen species living in mediterranean-type climates share common leaf traits irrespective of their different phylogenetic origin. [ABSTRACT FROM AUTHOR]

Background and Aims Understanding the genetic basis of adaptation and plasticity in trees constitutes a knowledge gap. We linked dendrochronology and genomics [single nucleotide polymorphisms (SNPs)] for a widespread conifer (Pinus halepensis Mill.) to characterize intraspecific growth differences elicited by climate. Methods The analysis comprised 20-year tree-ring series of 130 trees structured in 23 populations evaluated in a common garden. We tested for genotype by environment interactions (G × E) of indexed ring width (RWI) and early- to latewood ratios (ELI) using factorial regression, which describes G × E as differential gene sensitivity to climate. Key Results The species' annual growth was positively influenced by winter temperature and spring moisture and negatively influenced by previous autumn precipitation and warm springs. Four and five climate factors explained 10 % (RWI) and 16 % (ELI) of population-specific interannual variability, respectively, with populations from drought-prone areas and with uneven precipitation experiencing larger growth reductions during dry vegetative periods. Furthermore, four and two SNPs explained 14 % (RWI) and 10 % (ELI) of interannual variability among trees, respectively. Two SNPs played a putative role in adaptation to climate: one identified from transcriptome sequencing of P. halepensis and another involved in response regulation to environmental stressors. Conclusions We highlight how tree-ring phenotypes, obtained from a common garden experiment, combined with a candidate-gene approach allow the quantification of genetic and environmental effects determining adaptation for a conifer with a large and complex genome. [ABSTRACT FROM AUTHOR]

Dendrometers are being increasingly used to measure stem radius changes in trees and to unravel the mechanisms underlying stem daily rhythms of radial expansion and contraction. Nevertheless, automated dendrometers have not been often used to measure root radius dynamics, their relationship with environmental variables and the influence of endogenous processes, especially in drought-prone Mediterranean areas. Here, we measured root radius dynamics of two coexisting oak species (the evergreen Quercus ilex L. and the deciduous Quercus faginea Lam). Our goals were to describe annual, seasonal and diurnal scale root radius patterns and to disentangle the role of different environmental parameters as drivers. Long-term high-resolution measurements (every 15 min over 7 years) were collected with automated point dendrometers on the main tree roots of five individuals per species. Root radius annual change patterns were bimodal and similar for both oak species. Quercus faginea Lam showed three times larger root increment in the spring than Q. ilex , but the bimodal pattern was stronger in Q. ilex , which showed a larger root increment in autumn. Quercus faginea Lam showed an earlier root phenological activation in the spring and in late summer compared with Q. ilex. The effects of environmental drivers across species were similar at daily scales: root radius increased with air temperature and soil moisture, and it decreased with rising vapor pressure deficit. Furthermore, daily root radius variations for both oak species were maintained after extracting statistically the environmental effects, which points toward a significant role of endogenous drivers. These differences in root radius change patterns at seasonal to daily scales likely result from the differences in leaf phenology and growth strategy. Quercus faginea Lam is deciduous and has a faster growing rate in spring than the evergreen Q. ilex, which can grow more in summer. [ABSTRACT FROM AUTHOR]

Intraspecific variation in biomass production responses to elevated atmospheric carbon dioxide (eCO2) could influence tree species' ecological and evolutionary responses to climate change. However, the physiological mechanisms underlying genotypic variation in responsiveness to eCO2 remain poorly understood. In this study, we grew 17 Eucalyptus camaldulensis Dehnh. subsp. camaldulensis genotypes (representing provenances from four different climates) under ambient atmospheric CO2 and eCO2. We tested whether genotype leaf-scale photosynthetic and whole-tree carbon (C) allocation responses to eCO2 were predictive of genotype biomass production responses to eCO2. Averaged across genotypes, growth at eCO2 increased in situ leaf net photosynthesis (A net) (29%) and leaf starch concentrations (37%). Growth at eCO2 reduced the maximum carboxylation capacity of Rubisco (−4%) and leaf nitrogen per unit area (N area, −6%), but N area calculated on a total non-structural carbohydrate-free basis was similar between treatments. Growth at eCO2 also increased biomass production and altered C allocation by reducing leaf area ratio (−11%) and stem mass fraction (SMF, −9%), and increasing leaf mass area (18%) and leaf mass fraction (5%). Overall, we found few significant CO2 × provenance or CO2 × genotype (within provenance) interactions. However, genotypes that showed the largest increases in total dry mass at eCO2 had larger increases in root mass fraction (with larger decreases in SMF) and photosynthetic nitrogen-use efficiency (PNUE) with CO2 enrichment. These results indicate that genetic differences in PNUE and carbon sink utilization (in roots) are both important predictors of tree productivity responsiveness to eCO2. [ABSTRACT FROM AUTHOR]