Transpiration Rates, Climate and Soil Water Balance of Eucalyptus Grandis Afforestation on Temperate Grasslands in ne Argentina

Fast-growing Eucalyptus plantations evidence high rates of evapotranspiration. The increasing afforestation rates may affect local soil water balances. In this study, we measured transpiration rates in E. grandis at individual and stand level and we modeled it based on climate variables and soil water storage through a climate time series 1981-2010. We also estimated the aboveground net primary productivity and the water use efficiency based on regional empirical models. Transpiration rates were measured by the constant heat measurement method in 6 to 12 trees in three 100 m(2) plots in an 11-year-old plantation. The model fitted suggested that stand transpiration of E. grandis plantation near harvest age is limited by soil water storage and that the water table does not constitute an additional water source. The transpiration of E. grandis plantation was about 800 mm year(-1) which approximates 90% and 40% of the annual precipitation in dry and wet years, respectively. Our estimations compared well to other regional studies and suggest that stand transpiration, aboveground net primary productivity, and water use efficiency can be made based on simple climatic variables. A deeper discussion is needed to evaluate the impact of E. grandis transpiration rates at the regional scale.