© 2007 Heron Publishing—Victoria, Canada
Variability with xylem depth in sap flow in trunks and branches of mature olive trees
Nadezhda Nadezhdina (1, 4), Valeriy Nadezhdin (1), Maria Isabel Ferreira (2) and Andrea Pitacco (3)
1. Institute of Forest Ecology, Mendel University of Agriculture and Forestry, Zemedelska 3, 61300 Brno, Czech Republic / 2. Instituto Superior de Agronomia, The University of Lisbon, Tapada da Ajuda, 1349 017 Lisboa, Portugal / 3. Dept. of Environmental Agronomy and Crop Science, University of Padova, Agripolis, Via Romea 16, 35020 Legnaro (Padova), Italy / 4. Corresponding author (nadezdan@mendelu.cz) / Received September 21, 2005; accepted April 9, 2006; published online October 2, 2006
Summary
Knowledge of sap flow variability in tree trunks is important for up-scaling transpiration from the measuring point to the
whole-tree and stand levels. Natural variability in sap flow, both radial and circumferential, was studied in the trunks and
branches of mature olive trees (Olea europea L., cv Coratina) by the heat field deformation method using multi-point sensors. Sapwood depth ranged from 22 to 55 mm with
greater variability in trunks than in branches. Two asymmetric types of sap flow radial patterns were observed: Type 1, rising
to a maximum near the mid-point of the sapwood; and Type 2, falling continuously from a maximum just below cambium to zero
at the inner boundary of the sapwood. The Type 1 pattern was recorded more often in branches and smaller trees. Both types
of sap flow radial patterns were observed in trunks of the sample trees. Sap flow radial patterns were rather stable during
the day, but varied with soil water changes. A decrease in sap flow in the outermost xylem was related to water depletion
in the topsoil. We hypothesized that the variations in sap flow radial pattern in a tree trunk reflects a vertical distribution
of water uptake that varies with water availability in different soil layers.
Keywords:
automatic irrigation control, heat field deformation method, multi-point sensors, Quercus suber, sap flow radial pattern, vertical profile of root absorption, water stress indicator.
