Radial distribution of sap flux density in trunks of a mature beech stand

Abstract

-In a mature beech stand located in north-eastern Germany, xylem sap flux measurements were continuously performed during the 2002−2004 growing seasons. Ten representative trunks were studied using heated thermal dissipation probes. The measurements aimed at identifying principles governing radial profiles of xylem flux in beech trunks. The measurements were taken up to a trunk depth of 132 mm. The sap flow density in the pericambial xylem was found to vary among trees of different diameters, but was not considerably smaller in suppressed trees. A model for the radial distribution of sap flux density was formulated relating trunk radius and sap flow density. The model takes into account different trunk diameter. About 90% of the sap flux was found to occur in the outer two fifths of the trunk. Using this model, an adequate estimate of transpiration can be achieved at tree and stand level, even when the sap flux measurements are restricted to the outer trunk sectors. Les mesures ont été réalisées jusqu'à une profondeur de 132 mm. La densité de flux de sève du xylème de la zone cambiale variait d'arbre en arbre en fonction du diamètre, mais cette densité ne diminuait pas sensiblement dans les arbres dominés. Un modèle de distribution radiale de la densité de flux de sève a été mis au point dans lequel le diamètre du tronc et la densité du flux de sève sont mis en relation. Le modèle prend en considération les arbres ayant des troncs de diamètres différents. Environ 90 % de l'eau circule dans les deux cinquièmes extérieurs du tronc. De cette façon, il est possible de calculer de manière suffisamment exacte la transpiration de l'arbre ou du peuplement tout entier, même si les mesures du flux de sève se limitent à la zone externe du tronc. densité de flux de sève / modèle radial / hêtre

Within-stem maps of wood density and water content for characterization of species: a case study on three hardwood and two softwood species

“…In particular, softwood species have in general contrasting heartwood and sapwood (Lüttschwager and Remus 2007); this is not necessarily the case for hardwoods. For example, F. sylvatica does not show clear-cut delimitation between heartwood and sapwood, but rather a gradual transition (Gebauer et al 2008).…”

Variations de la consommation d’eau d’une mangrove adulte à Avicennia germinans, en Guyane française

“…The specific structure of the sapwood of A. germinans and the variability in its activity with the radial depth, the azimuth, the season and the tree age, prevent easy modeling of the distribution of SFD in the stems as in Lüttschwager and Remus (2007) for temperate species. In the rainforest, Granier et al (1996) made measurements using a single probe in the external tree ring and data were extrapolated to the entire sapwood whose apparent thickness was estimated visually from tree cores.…”

Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

“…The temperature difference over the heated segment was measured with two pairs of thermocouples mounted in 2-mm diameter stainless steel tubes inserted to a depth corresponding to 1/3 of the stem diameter. Water flow may vary with xylem depth in larger tree stems (Lüttschwager and Remus, 2007), but is assumed to be equal in small stems such as in this study. The first thermocouples above and below the heating band were placed at distances of 5 mm and 15 mm, respectively, and the other two were placed a further 5 mm above and below the first pair.…”