© 2000 Heron Publishing—Victoria, Canada
Radial variation in sap flow in five laurel forest tree species in Tenerife, Canary Islands
M. Soledad Jiménez (1), Nadezhda Nadezhdina (2), Jan Cermák (2) and Domingo Morales (1)
1. Dpto. de Biología Vegetal, Universidad de La Laguna, E-38207 La Laguna, Tenerife, Spain / 2. Institute of Forest Ecology, Mendel University of Agriculture and Forestry, 61300 Brno, Zemedelska 3, Czech Republic / Received July 30, 1999
Summary
Variations in radial patterns of xylem water content and sap flow rate were measured in five laurel forest tree species (Laurus azorica (Seub.) Franco, Persea indica (L.) Spreng., Myrica faya Ait., Erica arborea L. and Ilex perado Ait. ssp. platyphylla (Webb & Berth.) Tutin) growing in an experimental plot at Agua García, Tenerife, Canary Islands. Measurements were performed
around midday during warm and sunny days by the heat field deformation method. In all species, water content was almost constant
(around 35% by volume) over the whole xylem cross-sectional area. There were no differences in wood color over the whole cross-sectional
area of the stem in most species with the exception of E. arborea, whose wood became darker in the inner layers. Radial patterns of sap flow were highly variable and did not show clear relationships
with tree diameter or species. Sap flow occurred over the whole xylem cross-sectional area in some species, whereas it was
limited to the outer xylem layers in others. Sap flow rate was either similar along the xylem radius or exhibited a peak in
the outer part of the xylem area. Low sap flow rates with little variation in radial pattern were typical for shaded suppressed
trees, whereas dominant trees exhibited high sap flow rates with a peak in the radial pattern. Stem damage resulted in a significant
decrease in sap flow rate in the outer xylem layers. The outer xylem is more important for whole tree water supply than the
inner xylem because of its larger size. We conclude that measurement of radial flow pattern provides a reliable method of
integrating sap flow from individual measuring points to the whole tree.
Keywords:
conducting xylem, Erica arborea, Ilex perado, Laurus azorica, Myrica faya, Persea indica, radial pattern, sapwood, scaling, xylem water content.
