title: Explanatory ecological factors for the persistence of desiccation-sensitive seeds in transient soil seed banks: Quercus ilex as a case study.
abstract: OBJECTIVE
  Dominant tree species in northern temperate forests, for example oak and beech, produce desiccation-sensitive seeds. Despite the potentially major influence of this functional trait on the regeneration and distribution of species under climate change, little is currently known about the ecological determinants of the persistence of desiccation-sensitive seeds in transient soil seed banks. Knowing which key climatic and microsite factors favour seed survival will help define the regeneration niche for species whose seeds display extreme sensitivity to environmental stress
  
  
  METHODS
  Using the Mediterranean Holm oak (Quercus ilex) forest as a model system, an in situ time-course monitoring of seed water status and viability was performed during the unfavourable winter season in two years with contrasting rainfall, at an instrumented site with detailed climate records. In parallel, the characteristics of the microhabitat and their influence on the post-winter water status and viability of seeds were investigated in a regional survey of 33 woodlands representative of the French distribution of the species.
  
  
  RESULTS
  Time-course monitoring of seed water status in natural conditions confirmed that in situ desiccation is the main abiotic cause of mortality in winter. Critical water contents could be reached in a few days during drought spells. Seed dehydration rates were satisfactorily estimated using integrative climate proxies including vapour pressure deficit and potential evapotranspiration. Seed water status was therefore determined by the balance between water uptake after a rainfall event and water loss during dry periods. Structural equation modelling of microhabitat factors highlighted the major influence of canopy openness and resulting incident radiation on the ground.
  
  
  CONCLUSIONS
  This study provides part of the knowledge required to implement species distribution models which incorporate their regeneration niche. It is an important step forward in evaluating the ecological consequences of increasing winter drought and environmental filtering due to climate change on the regeneration of the most dominant Mediterranean tree species.
authors.affiliation: IRD, UMR DIADE, BP 64501, 34394 Montpellier, France and thierry.joet@ird.fr.
authors.forename: Thierry
authors.initials: T
authors.lastname: Joët
authors.affiliation: CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE, BP 5051, 34293 Montpellier, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Ourcival
authors.affiliation: IRD, UMR DIADE, BP 64501, 34394 Montpellier, France and.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Capelli
authors.affiliation: IRD, UMR DIADE, BP 64501, 34394 Montpellier, France and.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Dussert
authors.affiliation: CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE, BP 5051, 34293 Montpellier, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Morin
mesh_terms: D002980:Climate; D003890:Desiccation; D017753:Ecosystem; D005602:France; D007700:Kinetics; D008954:Models, Biological; D025341:Principal Component Analysis; D029963:Quercus / Q000502:physiology*; D012621:Seasons; D000068098:Seed Bank; D012639:Seeds / Q000502:physiology*; D013997:Time Factors; D055548:Vapor Pressure; D014867:Water
chemical_list: D014867:Water
keywords: Mediterranean climate; Quercus ilex; Recalcitrant seeds; desiccation; drought; environmental filtering; germination; microhabitat; oak acorn; regeneration niche; seed survival; structural equation modelling