Abstract

Water use by eucalypts has received a lot of attention in tropical countries during the past decade because of the large-scale introduction of these trees for afforestation. Eucalyptus grandis, widely used as a plantation item in tropical southern India, is the subject of a detailed ecophysiological study in this paper. A 4-year-old coppiced plantation was used for measurements. Microclimate data collected above the canopy were used along with stomatal conductance measurements to estimate the transpirational water loss by the Penman-Monteith equation assuming a two-layer canopy model. Leaf photosynthesis was measured diurnally and seasonally to understand the limitations in photosynthesis in the field. Results show that the water loss from the plantation ranges between 2. 5 and 6. 5 mm per day depending on the season. When suitably extrapolated, this amounts to 1181 mm annually in the study location, where annual rainfall averages 1302 mm. The stomatal conductance