Seasonal variation of water uptake of a Quercus suber tree in Central Portugal

Hydraulic redistribution (HR) is the phenomenon where plant roots transfer water between soil horizons of different water potential. When dry soil is a stronger sink for water loss from the plant than transpiration, water absorbed by roots in wetter soil horizons is transferred toward, and exuded into dry soil via flow reversals through the roots. Reverse flow is a good marker of HR and can serve as a useful tool to study it over the long-term. Seasonal variation of water uptake of a Quercus suber tree was studied from late winter through autumn 2003 at Rio Frio near Lisbon, Portugal. Sap flow was measured in five small shallow roots (diameter of 3–4 cm), 1 to 2 m from the tree trunk and in four azimuths and at different xylem depths at the trunk base, using the heat field deformation method (HFD). The pattern of sap flow differed among lateral roots as soil dried with constant positive flow in three roots and reverse flow in two other roots during the night when transpiration ceased. Rain modified the pattern of flow in these two roots by eliminating reverse flow and substantially increasing water uptake for transpiration during the day. The increase in water uptake in three other roots following rain was not so substantial. In addition, the flux in individual roots was correlated to different degrees with the flux at different radial depths and azimuthal directions in trunk xylem. The flow in outer trunk xylem seemed to be mostly consistent with water movement from surface soil horizons, whereas deep roots seemed to supply water to the whole cross-section of sapwood. When water flow substantially decreased in shallow lateral roots and the outer stem xylem during drought, water flow in the inner sapwood was maintained, presumably due to its direct connection to deep roots. Results also suggest the importance of the sap flow sensor placement, in relation to sinker roots, as to whether lateral roots might be found to exhibit reverse flow during drought. This study is consistent with the dimorphic rooting habit of Quercus suber trees in which deep roots access groundwater to supply superficial roots and the whole tree, when shallow soil layers were dry

Liberation du potassium par les fractions granulometriques du sol en presence de tetraphenylborate de sodium

National audienc

Determination des teneurs en eau du sol a l'aide de deux types d'humidimetrie

National audienc

Continuite des flux hydriques dans le systeme sol-racines-tronc. Cas des arbres fruitiers

National audienceA thermal method for measuring sap flow in apple-tree trunks and roots, combined with a water-soil transfer study has been utilized to investigate water transfer in a soil-plant system. It has been shown that: i) heterogeneities of sap flux are present in apple-tree trunk and root systems; ii) these heterogeneities are closely correlated and induced either by the heterogeneity of root density in moistened homogeneous soil or by the heterogeneity of different soil horizon wetting in moistened heterogeneous soil; and iii) the spatial distribution of daily water-soil loss is in agreement with the spatial distribution of water-soil extraction by the different root bundles. It has been concluded that a continuous flow exists between one soil sector, the root bundle present in that soil sector, and the trunk sector corresponding to the root bundle.L’analyse des flux de sève, mesurés par voie thermique, dans les racines et le tronc d’un pommier, couplée à l’étude des transferts de l’eau dans le sol, est utilisée pour étudier le transfert de celle-ci dans le système sol-plante. On montre qu’il existe une hétérogénéité des flux dans le tronc et entre les différents faisceaux racinaires de l’arbre, ces hétérogénéités étant bien corrélées. Leurs amplitudes dépendraient de l’hétérogénéité de densité racinaire en sol hydriquement homogène et en sol hydriquement hétérogène de l’hétérogénéité d’humectation locale des différents horizons du sol. La répartition spatiale des pertes en eau journalières mesurées dans le sol étant de plus bien corrélée à la structure spatiale des extractions d’eau par les racines primaires de l’arbre, on en conclut qu’il existe une continuité des flux entre un secteur de sol donné, le faisceau racinaire qu’il contient et le secteur du tronc correspondant au faisceau racinaire

Transfert d'eau dans le systeme sol-plante et pilotage de l'irrigation

Document interne *INRA, Station Science du sol Montfavet (FRA) Diffusion du document : INRA, Station Science du sol Montfavet (FRA)National audienc

Transfert d'eau dans le systeme sol-plante et pilotage de l'irrigation

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Orientation de recherches en matière d'irrigation goutte à goutte

* INRA, Centre de Recherche d'Avignon, Unite Regionale de Documentation, Montfavet;Document interne, Station de Science du Sol Diffusion du document : INRA, Centre de Recherche d'Avignon, Unite Regionale de Documentation, Montfavet;Document interne, Station de Science du SolNational audienc

La circulation de l'eau et des sels sous irrigation ponctuelle

International audienc

Cours de physique du sol appliquee a l'irrigation. Erevan, Octobre-Novembre 1991

Document interne;* INRA, Centre de Recherche d'Avignon, Station de Science du Sol, Montfavet (FRA) Diffusion du document : INRA, Centre de Recherche d'Avignon, Station de Science du Sol, Montfavet (FRA)National audienc