title: Changes in tracheid and ray traits in fire scars of North American conifers and their ecophysiological implications.
abstract: OBJECTIVE
  Fire scars have been widely used as proxies for the reconstruction of fire history; however, little is known about the impact of fire injury on wood anatomy. This study investigates changes in tracheid and ray traits in fire scars of Douglas fir (Pseudotsuga menziesii), western larch (Larix occidentalis) and ponderosa pine (Pinus ponderosa), and discusses their ecophysiological implications for tree recovery from fire.
  
  
  METHODS
  Transverse and tangential microsections were prepared for light microscopy and image analysis. Measurements of tracheids and rays were made in the three spatial dimensions: axially (at different section heights), radially (in different rings) and tangentially (with increasing distance from the wound margin).
  
  
  RESULTS
  Changes were strongest in the first year after fire injury, with a decrease in tracheid size (by 25-30 %) and an increase in tracheid density (by 21-53 %) for the three species. In addition, an increase in ray size (by 5-27 %) and an increase in ray density (by 19-36 %) were found in P. menziesii and L. occidentalis. Changes were comparable along the fire-injured stem and were often most marked close to the fire scar.
  
  
  CONCLUSIONS
  The differentiation after fire injury of narrower and more numerous tracheids expresses a trade-off between hydraulic safety and hydraulic efficiency, while that of larger and more numerous rays serves compartmentalization and wound closure, mechanical strength and defence responses. Pinus ponderosa does not generally produce more ray tissue after fire injury and thus appears to be more adapted to fire.
authors.affiliation: Dendrolab.ch, Institute of Geological Sciences, University of Berne, Berne, Switzerland arbellay@mail.ubc.ca.
authors.forename: Estelle
authors.initials: E
authors.lastname: Arbellay
authors.affiliation: Dendrolab.ch, Institute of Geological Sciences, University of Berne, Berne, Switzerland Climatic Change and Climate Impacts, Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Stoffel
authors.affiliation: USDA Forest Service, Rocky Mountain Research Station, Missoula, MT, USA.
authors.forename: Elaine K
authors.initials: EK
authors.lastname: Sutherland
authors.affiliation: USDA Forest Service, Northern Research Station, Durham, NH, USA.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Smith
authors.affiliation: School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, USA.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Falk
mesh_terms: D055669:Ecological and Environmental Phenomena; D005390:Fires; D009656:North America; D064028:Tracheophyta / Q000033:anatomy & histology*; D014197:Trees / Q000033:anatomy & histology; D014934:Wood / Q000033:anatomy & histology; D052584:Xylem / Q000033:anatomy & histology*
keywords: Douglas fir; Ecophysiology; Larix occidentalis; Pinus ponderosa; Pseudotsuga menziesii; conifer; fire scar; ponderosa pine; ray; tracheid; western larch; wood anatomy