title: Tree girdling responses simulated by a water and carbon transport model.
abstract: OBJECTIVE
  Girdling, or the removal of a strip of bark around a tree's outer circumference, is often used to study carbon relationships, as it triggers several carbon responses which seem to be interrelated.
  
  
  METHODS
  An existing plant model describing water and carbon transport in a tree was used to evaluate the mechanisms behind the girdling responses. Therefore, the (un)loading functions of the original model were adapted and became a function of the phloem turgor pressure.
  
  
  RESULTS
  The adapted model successfully simulated the measured changes in stem growth induced by girdling. The model indicated that the key driving variables for the girdling responses were changes in turgor pressure due to local changes in sugar concentrations. Information about the local damage to the phloem system was transferred to the other plant parts (crown and roots) by a change in phloem pressure. After girdling, the loading rate was affected and corresponded to the experimentally observed feedback inhibition. In addition, the unloading rate decreased after girdling and even reversed in some instances. The model enabled continuous simulation of changes in starch content, although a slight underestimation was observed compared with measured values.
  
  
  CONCLUSIONS
  For the first time a mechanistic plant model enabled simulation of tree girdling responses, which have thus far only been experimentally observed and fragmentally reported in literature. The close agreement between measured and simulated data confirms the underlying mechanisms introduced in the model.
authors.affiliation: Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Coupure links 653, B-9000 Ghent, Belgium. Veerle.DeSchepper@UGent.be
authors.forename: Veerle
authors.initials: V
authors.lastname: De Schepper
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
mesh_terms: D002244:Carbon / Q000378:metabolism*; D019069:Cell Respiration; D003198:Computer Simulation; D008834:Microclimate; D008954:Models, Biological; D009997:Osmotic Pressure; D052585:Phloem / Q000378:metabolism / Q000502:physiology; D010788:Photosynthesis; D024301:Plant Bark / Q000378:metabolism* / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D018547:Plant Stems / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D018526:Plant Transpiration; D029963:Quercus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D013213:Starch / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D014867:Water; D002244:Carbon; D013213:Starch