LAUREL FORESTS IN TENERIFE, CANARY-ISLANDS - THE ANNUAL COURSE OF SAPFLOW 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, T enerife, Canary Islands, over 1 year from June 1993 to May 1994. Sampl e 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. Maxim um transpiration for the stand was 7 mm day(-1). There was strong comp etition among the medium-sized trees in the high-density stand. The an nual course of transpiration was very variable, owing to weather condi tions, and was mainly controlled by the evaporative conditions. Contra sting with conditions in colder regions of the world with pronounced s easons, relatively high transpiration persisted over the mild winter. The annual total of transpiration was thus significantly higher, amoun ting to 636 mm year(-1) (about 500 mm from April to October). Neverthe less, the transpiration represented only a small portion of stand wate r balance (65% of potential evaporation and 80% of annual precipitatio n in the open).