title: The expression of light-related leaf functional traits depends on the location of individual leaves within the crown of isolated Olea europaea trees.
abstract: BACKGROUND
  The spatial arrangement and expression of foliar syndromes within tree crowns can reflect the coupling between crown form and function in a given environment. Isolated trees subjected to high irradiance and concomitant stress may adjust leaf phenotypes to cope with environmental gradients that are heterogeneous in space and time within the tree crown. The distinct expression of leaf phenotypes among crown positions could lead to complementary patterns in light interception at the crown scale.
  
  
  METHODS
  We quantified eight light-related leaf traits across 12 crown positions of ten isolated Olea europaea trees in the field. Specifically, we investigated whether the phenotypic expression of foliar traits differed among crown sectors and layers and five periods of the day from sunrise to sunset. We investigated the consequences in terms of the exposed area of the leaves at the tree scale during a single day.
  
  
  RESULTS
  All traits differed among crown positions except the length-to-width ratio of the leaves. We found a strong complementarity in the patterns of the potential exposed area of the leaves among day periods as a result of a non-random distribution of leaf angles across the crown. Leaf exposure at the outer layer was below 60 % of the displayed surface, reaching maximum interception during morning periods. Daily interception increased towards the inner layer, achieving consecutive maximization from east to west positions within the crown, matching the sun's trajectory.
  
  
  CONCLUSIONS
  The expression of leaf traits within isolated trees of O. europaea varies continuously through the crown in a gradient of leaf morphotypes and leaf angles depending on the exposure and location of individual leaves. The distribution of light-related traits within the crown and the complementarity in the potential exposure patterns of the leaves during the day challenges the assumption of low trait variability within individuals.
authors.affiliation: Department of Ecology, Faculty of Biology, Complutense University of Madrid, Jose Antonio Novais St., 28040 Madrid, Spain, adrianescribano@ucm.es.
authors.forename: Adrián G
authors.initials: AG
authors.lastname: Escribano-Rocafort
authors.affiliation: Department of Ecology, Faculty of Biology, Complutense University of Madrid, Jose Antonio Novais St., 28040 Madrid, Spain.
authors.forename: Agustina B
authors.initials: AB
authors.lastname: Ventre-Lespiaucq
authors.affiliation: Department of Plant Biology I, Faculty of Biology, Complutense University of Madrid, Jose Antonio Novais St., 28040 Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Granado-Yela
authors.affiliation: Department of Ecology, Facultad de Ciencias, Universidad de Granada, Avda. de la Fuentenueva s/n, 18071 Granada, Spain, Estación Experimental de Zonas Áridas, EEZA-CSIC, Carretera de Sacramento s/n, Almería, Spain and UMR 5175 CEFE - Centre d'Ecologie Fonctionnelle et Evolutive (CNRS), 1919 Route de Mende, F-34293 Montpellier cedex 05, France.
authors.forename: Rafael
authors.initials: R
authors.lastname: Rubio de Casas
authors.affiliation: Department of Ecology, Faculty of Biology, Complutense University of Madrid, Jose Antonio Novais St., 28040 Madrid, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Delgado
authors.affiliation: Department of Plant Biology I, Faculty of Biology, Complutense University of Madrid, Jose Antonio Novais St., 28040 Madrid, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Balaguer
mesh_terms: D008027:Light; D016014:Linear Models; D031658:Olea / Q000502:physiology* / Q000528:radiation effects*; D018515:Plant Leaves / Q000502:physiology* / Q000528:radiation effects*; D019655:Quantitative Trait, Heritable; D013997:Time Factors; D014197:Trees / Q000502:physiology* / Q000528:radiation effects*
keywords: Crown structure; Olea europaea; daily pattern; direct light; high irradiance; isolated trees; leaf angles; leaf exposure; leaf traits; variation within individuals