title: Seasonal changes in carbon and nitrogen compound concentrations in a Quercus petraea chronosequence.
abstract: Forest productivity declines with tree age. This decline may be due to changes in metabolic functions, resource availability and/or changes in resource allocation (between growth, reproduction and storage) with tree age. Carbon and nitrogen remobilization/storage processes are key to tree growth and survival. However, studies of the effects of tree age on these processes are scarce and have not yet considered seasonal carbon and nitrogen variations in situ. This study was carried out in a chronosequence of sessile oak (Quercus petraea Liebl.) for 1 year to survey the effects of tree age on the seasonal changes of carbon and nitrogen compounds in several tree compartments, focusing on key phenological stages. Our results highlight a general pattern of carbon and nitrogen function at all tree ages, with carbon reserve remobilization at budburst for growth, followed by carbon reserve formation during the leafy season and carbon reserve use during winter for maintenance. The variation in concentrations of nitrogen compounds shows less amplitude than that of carbon compounds. Storage as proteins occurs later, and mainly depends on leaf nitrogen remobilization and root uptake in autumn. We highlight several differences between tree age groups, in particular the loss of carbon storage function of fine and medium-sized roots with tree ageing. Moreover, the pattern of carbon compound accumulation in branches supports the hypothesis of a preferential allocation of carbon towards growth until the end of wood formation in juvenile trees, at the expense of the replenishment of carbon stores, while mature trees start allocating carbon to storage right after budburst. Our results demonstrate that at key phenological stages, physiological and developmental functions differ with tree age, and together with environmental conditions, influence the carbon and nitrogen concentration variations in sessile oaks.
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France.
authors.forename: Angélique
authors.initials: A
authors.lastname: Gilson
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Barthes
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Delpierre
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France.
authors.forename: Éric
authors.initials: É
authors.lastname: Dufrêne
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Fresneau
authors.affiliation: Université Paris-Sud, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France CNRS, UMR 8079, Laboratoire Ecologie Systématique et Evolution, Orsay, F-91405 Orsay, France AgroParisTech, UMR 8079, Laboratoire Ecologie Systématique et Evolution, F-75231 Paris, France stephane.bazot@u-psud.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bazot
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D005602:France; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D029963:Quercus / Q000254:growth & development / Q000378:metabolism*; D012621:Seasons; D014197:Trees / Q000254:growth & development / Q000378:metabolism
chemical_list: D000596:Amino Acids; D010940:Plant Proteins; D002244:Carbon; D009584:Nitrogen
keywords: ageing; non-structural carbohydrates; non-structural nitrogen compounds; phenology; remobilization; reserve formation; sessile oak; storage