Thu, Aug 05, 2021:On Demand
Background/Question/Methods
The Upper Mississippi River Floodplain Forest (UMR-FF) is located in the heart of the driftless region, an ecological system unique to the Midwest defined as an area unaffected by glacial drift from the last North American continental glacier. This diverse region is home to several characteristic plant species including the imperiled American elm (Ulmus americana). Studies have assumed ecological shifts in the UMR-FF as the historically dominant tree species and understory species have changed, creating intermittent habitats and raising concerns for tree regeneration of the American elm. A recent UMR-FF inventory dataset considering a variety of parameters (pool location and American elm canopy class, health class and diameter at breast height) was analyzed to determine trends in health and population characteristics of the American elm population.
Results/Conclusions Analysis revealed American elm differences between northern UMR-FF from Hastings, MN to Genoa, WI and southern UMR-FF from Lynxville, WI to Guttenburg, IA suggesting shifting regime trends. Over 50% of the elm in the inventory were found in southern pools showing a decline of elms in northern populations. Trends also reveal a decline in healthy elm characteristics within northern pools where healthy trees and co-dominant canopies were less common compared to the elms in southern pools. With the absence of the American elm’s broad crown, the UMR-FF is facing a change in understory species leading to subsequent shifts in all tiers of forest vegetation. There are multiple factors, including understory invasive species, Dutch Elm Disease infection rates, hydrological fluctuations, and deer herbivory that may influence native tree regeneration, but we require additional data to understand the impacts on the American elm and the historically prominent tree species of the UMR-FF.
Results/Conclusions Analysis revealed American elm differences between northern UMR-FF from Hastings, MN to Genoa, WI and southern UMR-FF from Lynxville, WI to Guttenburg, IA suggesting shifting regime trends. Over 50% of the elm in the inventory were found in southern pools showing a decline of elms in northern populations. Trends also reveal a decline in healthy elm characteristics within northern pools where healthy trees and co-dominant canopies were less common compared to the elms in southern pools. With the absence of the American elm’s broad crown, the UMR-FF is facing a change in understory species leading to subsequent shifts in all tiers of forest vegetation. There are multiple factors, including understory invasive species, Dutch Elm Disease infection rates, hydrological fluctuations, and deer herbivory that may influence native tree regeneration, but we require additional data to understand the impacts on the American elm and the historically prominent tree species of the UMR-FF.