Growth and water balance of Eucalyptus grandis hybrid plantations in Brazil during a rotation for pulp production

The water balance and growth of Eucalyptus grandis hybrid plantations in Brazil are presented based on 6 years of intensive catchment hydrology, physiological and forest growth surveying, and modelling. The results show a balance between water supply by precipitation and output through evapotranspiration (considered as canopy interception, soil evaporation and trees transpiration) and runoff. The annual average precipitation was 1147 mm and average evapotranspiration was 1092 mm. The runoff was only 3% of the precipitation, because of high soil infiltration and the flat topography where the trees are planted. Evapotranspiration rates varied from 781 mm to 1334 mm during the years of the study and are strongly influenced by variations in annual precipitation and leaf area index. When the precipitation was close to the regional mean annual precipitation of 1350 mm there was enough water to supply the demands of the trees and produce some runoff. Biomass production was high and the peak annual growth rate was 95 m3 ha−1 year−1. The UAPE model [Soares, J.V., Almeida, A.C., 2001. Modeling the water balance and soil water fluxes in a fast-growing Eucalyptus plantation in Brazil. J. Hydrol. 253, 130–147] was used to estimate the water balance and the widely used 3-PG model [Landsberg, J.J., Waring, R.H., 1997. A generalised model of forest productivity using simplified concepts of radiation-use efficiency, carbon balance and partitioning. For. Ecol. Manage. 95, 209–228] was used to estimate forest growth and water-use efficiency.