title: Separating water-potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal.
abstract: The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water-potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field-measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water-potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late-summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water-potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.
authors: Department of Forest Ecology, University of Helsinki, Helsinki, FIN-00014, Finland.
authors: Tommy
authors: T
authors: Chan
authors: Department of Forest Ecology, University of Helsinki, Helsinki, FIN-00014, Finland.
authors: Teemu
authors: T
authors: Hölttä
authors: Department of Forest Ecology, University of Helsinki, Helsinki, FIN-00014, Finland.
authors: Frank
authors: F
authors: Berninger
authors: Finnish Forest Research Institute, Vantaa, FIN-01301, Finland.
authors: Harri
authors: H
authors: Mäkinen
authors: Finnish Forest Research Institute, Vantaa, FIN-01301, Finland.
authors: Pekka
authors: P
authors: Nöjd
authors: School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JN, UK.
authors: Maurizio
authors: M
authors: Mencuccini
authors: Department of Forest Ecology, University of Helsinki, Helsinki, FIN-00014, Finland.
authors: Eero
authors: E
authors: Nikinmaa
mesh_terms: D058506:Cambium / Q000254:growth & development*; D004777:Environment; D009995:Osmosis; D017785:Photons; D010788:Photosynthesis; D018547:Plant Stems / Q000254:growth & development / Q000502:physiology*; D011312:Pressure; D011891:Rain; D012044:Regression Analysis; D012621:Seasons; D013696:Temperature; D014867:Water / Q000502:physiology*; D052584:Xylem / Q000502:physiology
chemical_list: D014867:Water
keywords: dendrometer; elasticity; hydraulic conductance; phloem; xylem