Reforesting the jack pine barrens: a long-term common garden experiment

Long-term common garden experiments provide the unique opportunity to assess the individual life-long and regeneration response of different tree species to their shared environment. The survival, growth, and regeneration of three locally native, 22 regionally native, and 16 nonnative (exotic to North America) tree species were measured in a common garden experiment established in 1888 on the jack pine barrens of northern lower Michigan. None of the stems from the 32 hardwood species survived. The conifers Pinus resinosa (35%), Picea abies (24%), and Pinus strobus (7%) had the highest survival of original stems; several stems of Juniperus virginiana, Picea glauca, Pinus rigida, and Thuja occidentalis also survived. Regeneration was dominated by Pinus strobus, P. resinosa, Picea abies, and Pinus sylvestris in the plantation and by P. strobus, unplanted P. banksiana, P. sylvestris, and unplanted Quercus spp. in the old field next to the plantation. Regeneration from Prunus serotina, Populus alba, Robinia pseudoacacia, Fraxinus americana, Acer rubrum, and A. platanoides was present in the plantation and/or adjacent old field. The survival, relatively low productivity (site indices of 28–29 for Picea spp. and 44–45 for Pinus resinosa and P. strobus), and regeneration of the species planted at this site indicate that P. resinosa is the best species for wood production while P. strobus would be best to provide long-term forest cover. The nonnative Pinus sylvestris and Picea abies performed as well as or better than species native to the jack pine barrens. Pinus sylvestris is successfully recruiting outside of the original plantation next to the native early successional species P. banksiana and P. strobus. Within the plantation, Picea abies had high survival and regenerated as much as the native dominant Pinus strobus. The naturalization of nonnative Pinus sylvestris and Picea abies in this plantation suggests that these species have the potential to become invasive in the jack pine barren ecosystem.