© 2004 Heron Publishing—Victoria, Canada
Radial profiles of sap flow with increasing tree size in maritime pine
Sylvain Delzon (1, 2), Michel Sartore (1), André Granier (3) and Denis Loustau (1)
1. Unité-EPHYSE, INRA, 69 route d’Arcachon, 33612 GAZINET Cedex, France / 2. Corresponding author (delzon@pierroton.inra.fr) / 3. Laboratoire d’Ecologie et Ecophysiologie Forestières, UMR INRA - Université Nancy I, 54280 Champenoux, France / Received December 15, 2003; accepted April 18, 2004; published online September 1, 2004
Summary
We investigated the radial variation of sap flow within sapwood below the live crown in relation to tree size in 10-, 32-,
54- and 91-year-old maritime pine stands (Pinus pinaster Ait.). Radial variations were determined with two thermal dissipation sensors; one measured sap flux in the outer 20 mm of
the xylem (Jref), whereas the other was moved radially across the sapwood in 20-mm increments to measure sap flux at multiple depths (Jref). For all tree sizes, sap flow ratios (Ri = JiJref–1) declined with increasing sapwood depth, but the decrease was steeper in trees with large diameters. Correction factors (C) were calculated to extrapolate Jref for an estimate of whole-tree sap flux. A negative linear relationship was established between stem diameter and C, the latter ranging from 0.6 to 1.0. We found that neglecting these radial corrections in 10-, 32-, 54- and 91-year-old trees
would lead to overestimation of stand transpiration by 4, 14, 26 and 47%, respectively. Therefore, it is necessary to account
for the differential radial profiles of sap flow in relation to tree size when comparing tree transpiration and hydraulic
properties among trees differing in size.
Keywords:
correction factor, heat dissipation method, Pinus pinaster, sap flux, tree size effect.
