An evaluation of Alnus (alder) germplasm in five diverse nonagricultural environments in Minnesota (USA)

To reach the goal set by the United States Department of Energy to replace 30% of 2004 gasoline usage with biofuels by 2030, the U.S. will need to consider diverse biomass feedstock sources, such as the plant genus Alnus. This genus contains nitrogen-fixing species that grow in a wide variety of challenging conditions. This study focused on 13 species of Alnus and was designed to determine survival, and above ground biomass production in five diverse environments unsuitable for food production agriculture in Minnesota, USA. Additionally, seven Salix and four Populus selections, that have been tested in short rotation woody biomass systems, were included for comparative analysis. Ten of the 13 Alnus species died from winter injury at all locations or produced above ground biomass at levels well below individual site averages. These ten Alnus species are not well suited for the soils and climate in the upper Great Lakes region. However, three species, A. glutinosa, A. incana, and A. viridis exceeded 90% survival at all five sites and produced significantly more aboveground biomass than the other Alnus species. On a low-nitrogen site with coarse sandy soils, the three species produced an average of 5.35 megagrams per hectare of above ground biomass over a three year period. This exceeded the biomass production of all other materials in the trial including commercially available Populus and Salix selections confirming the a priori expectation that Alnus' potential symbiosis with nitrogen-fixing bacteria promotes increased growth on low fertility soils.