Research Investigating Aspen Decline in Niobrara Valley

Research was initiated in 2015 to understand what may be causing a decline in the extent of hybrid aspen trees along the Niobrara River.

The hybrids (Populus xsmithii) are a genetic mix of the quaking aspen (Populus tremuloides) and bigtooth aspen (Populus grandidentata).

Two primary tasks were completed during the year.

1) “Leaf material for genetic analysis” and “root cuttings for clonal propagation in greenhouse experiments” were collected by Nick Deacon, a postdoctoral associate, and Jake Grossman, a graduate student, according to a project report provided to the National Park Service, the project sponsor. Both are from the University of Minnesota.

Root cuttings were collected from “all Niobrara aspens stands of as well as stands of quaking aspen and big toothed aspen from NE, SD, MN, IA, and WI.

2) An analysis of aspen stand condition at Smith Falls State Park was completed by James Robinson, a graduate student at the University of South Dakota. Also evaluated were the “effects of herbivory and management on growth and condition of aspen suckers. Findings provided implications for future management of aspen stands.”

Two manuscripts were prepared from these analyses, the report said.

The unique hybrid aspens – relicts of a Pleistocene age northern boreal forest - occur in the cool and moist spring-branch canyons along the river, notably on the southern slope of the Niobrara valley. The stands are currently in decline, “due to pathogen infestations, fire suppression, competition with invasive red cedar, ungulate browsing, drought stress and potentially changes in the spring freeze-thaw cycles due to climate change,” according to the project proposal.

“An understanding of the genetic diversity and hybrid status, age structure and health, ecological niche and historical rate of range contraction, and drought and freezing tolerance physiology, is of paramount importance for understanding the fate of these important heritage organisms,” the proposal said.

This is a three year project, financed by the Niobrara National Scenic River office of the National Park Service at Valentine. The project grant was for $381,439.81.