Water use of a bioenergy plantation increases in a future high CO2 world

Tricker, P.J., Pecchiari, M., Bunn, S.M., Vaccari, F.P., Peressotti, A., Miglietta, F. and Taylor, G. (2009) Water use of a bioenergy plantation increases in a future high CO2 world. Biomass and Bioenergy, 33 (2). pp. 200-208. ISSN 0961-9534 doi: 10.1016/j.biombioe.2008.05.009

Abstract/Summary

Fast-growing poplar trees may in future be used as a source of renewable energy for heat, electricity and biofuels such as bioethanol. Water use in Populus x euramericana (clone I214), following long-term exposure to elevated CO2 in the POPFACE (poplar free-air carbon dioxide enrichment) experiment, is quantified here. Stomatal conductance was measured and, during two measurement campaigns made before and after coppicing, whole-tree water use was determined using heat-balance sap-flow gauges, first validated using eddy covariance measurements of latent heat flux. Water use was determined by the balance between leaf-level reductions in stomatal conductance and tree-level stimulations in transpiration. Reductions in stomatal conductance were found that varied between 16 and 39% relative to ambient air. Whole-tree sap flow was increased in plants growing under elevated CO2, on average, by 12 and 23%, respectively, in the first and in the second measurement campaigns. These results suggest that future CO2 concentrations may result in an increase in seasonal water use in fast-growing, short-rotation Populus plantations.