Laurel forests in Tenerife, Canary Islands: The annual course of sap flow in Laurus trees and stand

Sap flow rate was continuously measured in six trees of Laurus azorica at the experimental site of laurel forest in Agua Garcia mountains, Tenerife, Canary Islands, over 1 year from June 1993 to May 1994. Sample trees were of different sizes and covered the whole range of species. A sigmoid-like relationship based on basal area was applied to scale up the transpiration data from sample trees to the whole stand. Maximum transpiration for the stand was 7 mm day(-1). There was strong competition among the medium-sized trees in the high-density stand. The annual course of transpiration was very variable, owing to weather conditions, and was mainly controlled by the evaporative conditions. Contrasting with conditions in colder regions of the world with pronounced seasons, relatively high transpiration persisted over the mild winter. The annual total of transpiration was thus significantly higher, amounting to 636 mm year(-1) (about 500 mm from April to October). Nevertheless, the transpiration represented only a small portion of stand water balance (65% of potential evaporation and 80% of annual precipitation in the open).