title: Kinetics of tracheid development explain conifer tree-ring structure.
abstract: Conifer tree rings are generally composed of large, thin-walled cells of light earlywood followed by narrow, thick-walled cells of dense latewood. Yet, how wood formation processes and the associated kinetics create this typical pattern remains poorly understood. We monitored tree-ring formation weekly over 3 yr in 45 trees of three conifer species in France. Data were used to model cell development kinetics, and to attribute the relative importance of the duration and rate of cell enlargement and cell wall deposition on tree-ring structure. Cell enlargement duration contributed to 75% of changes in cell diameter along the tree rings. Remarkably, the amount of wall material per cell was quite constant along the rings. Consequently, and in contrast with widespread belief, changes in cell wall thickness were not principally attributed to the duration and rate of wall deposition (33%), but rather to the changes in cell size (67%). Cell enlargement duration, as the main driver of cell size and wall thickness, contributed to 56% of wood density variation along the rings. This mechanistic framework now forms the basis for unraveling how environmental stresses trigger deviations (e.g. false rings) from the normal tree-ring structure.
authors.affiliation: INRA, UMR 1092 LERFOB, F-54280, Champenoux, France.
authors.forename: Henri E
authors.initials: HE
authors.lastname: Cuny
authors.affiliation: INRA, UMR 1092 LERFOB, F-54280, Champenoux, France.
authors.forename: Cyrille B K
authors.initials: CBK
authors.lastname: Rathgeber
authors.affiliation: Swiss Federal Research Institute WSL, CH-8903, Birmensdorf, Switzerland.|Oeschger Centre for Climate Change Research, CH-3012, Bern, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Frank
authors.affiliation: Swiss Federal Research Institute WSL, CH-8903, Birmensdorf, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Fonti
authors.affiliation: AgroParisTech, UMR 1092 LERFOB, F-54000, Nancy, France.
authors.forename: Meriem
authors.initials: M
authors.lastname: Fournier
mesh_terms: D005602:France; D007700:Kinetics; D008954:Models, Biological; D064028:Tracheophyta / Q000033:anatomy & histology* / Q000254:growth & development*; D014197:Trees / Q000033:anatomy & histology* / Q000254:growth & development; D014934:Wood / Q000033:anatomy & histology / Q000254:growth & development; D052584:Xylem / Q000254:growth & development*
keywords: cambial activity; conifers; generalized additive models (GAMs); kinetics of tracheid development; quantitative wood anatomy; tree-ring structure; wood density; xylogenesis