Early stand production of hybrid poplar and white spruce in mixed and monospeciﬁc plantations in eastern Maine A. S. Nelson • M. R. Saunders • R. G. Wagner • A. R. Weiskittel Received: 22 March 2011 / Accepted: 29 November 2011 / Published online: 14 December 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Forest plantations in the northeastern United States comprise a small propor- tion of the total forest area. Most plantations are typically softwood dominated and managed for sawlog and pulpwood production, while high-yield hardwood plantations for bioenergy feedstocks have not been as widely investigated. The objective of this study was to compare the biomass production of planted white spruce (Picea glauca (Moench) Voss) and hybrid poplar (Populus spp.) plantations (four clones) in monoculture, and in mixture of the two on a typical reforestation site in Maine. Three years following planting, hybrid poplar height and ground line diameter growth rates began to diverge among clones, and by 6 years, the Populus nigra 9 Populus maximowiczii (NM6) clone clearly outperformed three Populus deltoides 9 Populus nigra clones (D51, DN10 and DN70) both in pure stands and in mixtures with white spruce. In mixture, we found the yield of white spruce to decline as the yield of hybrid poplar increased. Overall, yields of white spruce monocul- tures were comparable to those reported in eastern Canada, while the hybrid poplar bio- mass yields were substantially lower than those reported from studies on abandoned agricultural lands, likely due to the harsher soil conditions at our site. The dominance of rocky and poorly drained sites (like the one tested in this study) across Maine will likely limit the feasibility of widespread hybrid poplar plantations, and thus constrains their potential use as a bioenergy feedstock. Keywords Mixed-species plantations  Biomass production  Short-rotation hardwoods  Bioenergy feedstock  Harsh-site regeneration A. S. Nelson (&)  R. G. Wagner  A. R. Weiskittel School of Forest Resources, University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755, USA e-mail: andrew.s.nelson@maine.edu M. R. Saunders Department of Forestry and Natural Resources, Purdue University, 715 W. State St., West Lafayette, IN 47907-2061, USA 123 New Forests (2012) 43:519–534 DOI 10.1007/s11056-011-9296-2