LONG-TERM TRANSPIRATION IN 2 EUCALYPT SPECIES IN A NATIVE WOODLAND ESTIMATED BY THE HEAT-PULSE TECHNIQUE

The heat-pulse method was used to estimate transpiration rates continu ously for periods up to 2 years in mature trees of Eucalyptus wandoo a nd Eucalyptus salmonophloia at two topographic locations in a remnant native woodland in the Western Australian wheatbelt. Annual transpirat ion per tree ranged from about 11 400 to 18 000 L per tree. Highest tr anspiration rates occurred in late spring or early summer, depending o n rainfall distribution. The trees were able to rapidly utilize water following heavy rain outside the agricultural growing season. Extrapol ating transpiration rates from single trees to an area of woodland sho wed that annual transpiration at the ridge site was 150 mm and 168 mm at a site alongside a drainage line. Scaling up transpiration from ind ividual trees requires caution and should allow for variability in tre es and soils. The role of trees in curtailing salinization is discusse d.