CDR LTER

Quaking aspen (Populus tremuloides) is the most cosmopolitan tree species in North America and an important native at Cedar Creek and across the Midwest. Aspen stands are quite common through eastern, central, and northern Minnesota, and occur sporadically in cool, wet microclimates across the Great Plains. Currently, these stands are in decline, are poorly reproducing in the wild, and are suffering from a range of stresses. Climate change associated phenomena, drought and altered freeze-thaw cycles, have contributed to massive aspen dieback, especially in the American West. We have received funding from the National Park Service to assess the genetic diversity and hybrid status, age structure and health, ecological niche and historical rate of range contraction, and drought and freezing tolerance physiology of an aspen stand of interest at the Niobrara National Scenic River (NNSR) in northern Nebraska. As part of this project, we are also studying genetic diversity and physiological vulnerability to climate change in quaking and bigtooth (P. grandidentata) aspen populations in Minnesota, Wisconsin, Iowa, South Dakota, and Nebraska. We will use genetic markers to identify genetically unique stands and compare growth and survival of these to populations of the parent species under different drought and freeze-thaw conditions. This study will allow us to better pinpoint the causes of decline in the NNSR aspen stands and aspen stands across the upper Midwest, and potentially provide guidance to managers on the prioritization of particular stands for conservation or in identifying genetic sources for any ex situ conservation or assisted migration.