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Below‐ground hydraulic conductance is a function of environmental conditions and tree size in Scots pine
Author(s) -
MARTÍNEZVILALTA J.,
KORAKAKI E.,
VANDERKLEIN D.,
MENCUCCINI M.
Publication year - 2007
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/j.1365-2435.2007.01332.x
Subject(s) - scots pine , water transport , hydraulic conductivity , xylem , biology , transpiration , stomatal conductance , water flow , environmental science , ecology , hydrology (agriculture) , botany , atmospheric sciences , soil water , soil science , photosynthesis , pinus <genus> , physics , engineering , geotechnical engineering
Summary1 Variations in water tension in a transpiring tree cause elastic changes in stem diameter. To better understand the dynamics of these variations, stem diameter changes and sap flow rates were monitored simultaneously in trees from two Scots pine chronosequences in Scotland. 2 Tree below‐ground hydraulic conductance ( k bg ) was estimated from the relationship between leaf‐specific sap flow rates and the difference between stem and soil water potentials estimated from diameter variations in the stem. 3 In a given tree, k bg varied both within and among days, with conductance increasing as a function of sap flow and evaporative demand. These patterns could be explained in terms of a composite model of root water transport and possible changes in the gating of aquaporins. 4 We interpreted these trends of increasing k bg with evaporative demand as a mechanism to enhance the ability of trees to control leaf water potential and keep it within physiologically acceptable limits, with potential implications for our general understanding of plant water relations, and for the estimation and modelling of ecosystem water fluxes. 5 Across trees, k bg declined with increasing tree age/size, but the proportional contribution of below‐ground to whole‐tree hydraulic resistance also declined. This is consistent with an increase in below‐ground carbon allocation in old/tall trees and a partial acclimation of tall trees to hydraulic limitations. It is argued that these trends have to be considered when discussing the importance of tree height for water transport and growth.