title: Functional and environmental determinants of bark thickness in fire-free temperate rain forest communities.
abstract: OBJECTIVE
  In fire-prone ecosystems, variation in bark thickness among species and communities has been explained by fire frequency; thick bark is necessary to protect cambium from lethal temperatures. Elsewhere this investment is deemed unnecessary, and thin bark is thought to prevail. However, in rain forest ecosystems where fire is rare, bark thickness varies widely among species and communities, and the causes of this variation remain enigmatic. We tested for functional explanations of bark thickness variation in temperate rain forest species and communities.
  
  
  METHODS
  We measured bark thickness in 82 tree species throughout New Zealand temperate rain forests that historically have experienced little fire and applied two complementary analyses. First, we examined correlations between bark traits and leaf habit, and leaf and stem traits. Second, we calculated community-weighted mean (CWM) bark thickness for 272 plots distributed throughout New Zealand to identify the environments in which thicker-barked communities occur.
  
  
  RESULTS
  Conifers had higher size-independent bark thickness than evergreen angiosperms. Species with thicker bark or higher bark allocation coefficients were not associated with "slow economic" plant traits. Across 272 forest plots, communities with thicker bark occurred on infertile soils, and communities with thicker bark and higher bark allocation coefficients occurred in cooler, drier climates.
  
  
  CONCLUSIONS
  In non-fire-prone temperate rain forest ecosystems, investment in bark is driven by soil resources, cool minimum temperatures, and seasonal moisture stress. The role of these factors in fire-prone ecosystems warrants testing.
authors.affiliation: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand RichardsonS@LandcareResearch.co.nz.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Richardson
authors.affiliation: Environmental Research Institute, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Laughlin
authors.affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT 0909, Australia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lawes
authors.affiliation: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Holdaway
authors.affiliation: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand Joint Graduate School in Biodiversity and Biosecurity, School of Environment, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Wilmshurst
authors.affiliation: Ecology Department, Lincoln University, PO Box 85084, Lincoln 7647, New Zealand.
authors.forename: Monique
authors.initials: M
authors.lastname: Wright
authors.affiliation: Ecology Department, Lincoln University, PO Box 85084, Lincoln 7647, New Zealand.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Curran
authors.affiliation: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Bellingham
authors.affiliation: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand.
authors.forename: Matt S
authors.initials: MS
authors.lastname: McGlone
mesh_terms: D005390:Fires; D019684:Magnoliopsida / Q000033:anatomy & histology*; D009520:New Zealand; D024301:Plant Bark / Q000033:anatomy & histology*; D065947:Rainforest; D064028:Tracheophyta / Q000033:anatomy & histology*; D014197:Trees / Q000033:anatomy & histology
keywords: allometry; community-weighted mean; environmental filtering; fire history; functional trait; pathogens; plant economics spectrum; size-independent bark traits