GreenWood Resources proposes to develop hybrid poplar growing stock of improved water-use efficiency using a strategy of species selection, inter-specific hybridization, and varietal selection. The proposed work will lead to an increase in the cost-efficiency of current sawlog production and future biomass production at GreenWood's Boardman Tree Farm. Improvement in the physiology of varietal water use efficiency will also lead to reductions in greenhouse gas emission. Moreover, growing stock of improved water use efficiency will enable short-rotation forestry as a renewable source of cellulosic energy feedstock on sites of marginal agricultural quality using low-input silviculture in targeted regions of the western United States. The water-use efficient hybrid poplar energy varieties developed in this project will initially be used in developing biomass feedstock plantation support for a local cellulosic bio-refinery.