title: Are trees able to grow in periods of stem shrinkage?
abstract: Separating continuously measured stem radius (SR) fluctuations into growth-induced irreversible stem expansion (GRO) and tree water deficit-induced reversible stem shrinkage (TWD) requires a conceptualization of potential growth processes that may occur during periods of shrinking and expanding SR below a precedent maximum. Here, we investigated two physiological concepts: the linear growth (LG) concept, assuming linear growth, versus the zero growth (ZG) concept, assuming no growth during periods of stem shrinkage. We evaluated the physiological mechanisms underlying these two concepts and assessed their respective plausibilities using SR data obtained from 15 deciduous and evergreen trees. The application of the LG concept produced steady growth rates, whereas growth rates varied strongly under the ZG concept, more in accordance with mechanistic expectations. Further, growth increased for a maximum of 120 min after periods of stem shrinkage, indicating limited growth activity during those periods. However, this extra growth was found to be a small fraction of total growth only. Furthermore, TWD under the ZG concept was better explained by a hydraulic plant model than TWD under the LG concept. We conclude that periods of stem shrinkage allow for very little growth in the four tree species investigated. However, further studies should focus on obtaining independent growth data to ultimately validate these findings.
authors.affiliation: Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zurcherstrasse 111, Birmensdorf, CH-8903, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Zweifel
authors.affiliation: Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zurcherstrasse 111, Birmensdorf, CH-8903, Switzerland.|Institute of Agricultural Sciences, ETH Zurich, Universitatstrasse 2, Zurich, 8092, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Haeni
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitatstrasse 2, Zurich, 8092, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Buchmann
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitatstrasse 2, Zurich, 8092, Switzerland.
authors.forename: Werner
authors.initials: W
authors.lastname: Eugster
mesh_terms: D018547:Plant Stems / Q000502:physiology*; D014197:Trees / Q000254:growth & development* / Q000502:physiology; D055548:Vapor Pressure; D014867:Water / Q000502:physiology; D014887:Weather
chemical_list: D014867:Water
keywords: TreeNet; bark shrinkage; cambial activity; point dendrometer; stem diameter variations; tree ring; tree water relations; wood growth