Transpiration from Eucalyptus sieberi (L. Johnson) forests of different age

We measured transpiration, sapwood areas, and leaf areas of individual trees in three stands of Eucalyptus sieberi, aged 14, 45, and 160 years. Transpiration was calculated from estimates of sap velocity made by the heat-pulse method. Sapwood and leaf areas were determined by destructive sampling. Leaf area index (LAI), sapwood area and transpiration of the plots in the three stands were estimated. Mean sap velocity of trees in the three plots in late summer (February-March) was not significantly different and averaged 9.5 cm h(-1). Diameter was a good predictor of sapwood area and leaf area of individual trees. Diameter predicted 94% of the variation in sapwood area and 96% of the variation in leaf area. Stand sapwood area declined with age from 11 m(2) ha(-1) in the 14 year old forest, to 6.5 m(2) ha(-1) in the 45 year old forest, to 3.1 m(2) ha(-1) in the 160 year old forest. LAI was 3.6, 4.0, and 3.4 for the 14, 45, and 160 year old plots, respectively, Because of the difference in sapwood area, plot transpiration declined with age from 2.2 mm per day in 14 year old forest, 1.4 mm per day in 45 year old forest, to 0.8 mm per day in 160 year old forest. (C) 2001 Elsevier Science B.V. All rights reserved.