Determining drivers of floodplain forest regeneration success and failure on the Upper Mississippi River in Minnesota and Wisconsin

The floodplain forests of the Upper Mississippi River (UMR) Basin play a critical role in maintaining water quality, wildlife habitat, and recreational opportunities. However, these forests systems are not static. Interactions among shifting climatic patterns, invasive species (especially reed canarygrass (Phalaris arundinacea)), forest health (e.g. Dutch elm disease and emerald ash borer), herbivores, low tree species diversity, and aging stands with limited regeneration are threatening to push these forest communities past critical ecological “tipping points.” These tipping points lead to drastic shifts in community composition and structure (e.g. conversion to non-forest conditions), making ecosystem restoration and rehabilitation significantly more difficult and greatly reducing the resilience of these systems. Within the UMR floodplain in Minnesota, Wisconsin and northeast Iowa (UMR Pools 1-10), this problem is particularly acute – current forest inventory data indicates that forest regeneration is completely absent over 57% of inventory plots and of the areas. Of the remaining plots with documented regeneration, almost 25% of plots are dominated by ash or elm regeneration, but both of these species have minimal potential for long-term survival on the sites due to insects and diseases. Without viable regeneration, these forests will convert to non-forest cover types in coming decades as current canopy trees begin to die. Proactive management actions can aid in reducing the chance of future forest loss, but there is limited research or institutional knowledge along the Upper Mississippi available on the mechanisms driving regeneration of key floodplain forest tree species and, therefore, management actions to promote regeneration of trees often result in failure. The current study aims to identify key drivers of regeneration for a handful of currently widespread floodplain forest tree species and to test a set of management techniques to promote the establishment of regeneration from seed. This information is critical for developing management strategies to ensure long-term viability of UMR Floodplain Forests.The primary goal of this research is to identify factors in existing floodplain forests on the Upper Mississippi River in Minnesota, Wisconsin and northeast Iowa that are associated with establishment and growth of regeneration from seed and planted tree seedlings in the most northern reach of the navigable portion of the Upper Mississippi River. Understanding dynamics of light-seeded species, primarily eastern cottonwood (Populous deltoides), silver maple (Acer saccharinum) and river birch (Betula nigra) is critical to this study, but other floodplain species may be incorporated as well. The research will also aim to test a set of silvicultural approaches for promoting natural regeneration in this region based on the current understanding of the silvics of these species. Because light availability, flood inundation, and soil saturation are key drivers of tree species distribution in these floodplains, the research will focus on assessing regeneration conditions across gradients of these drivers.
Categories: Science and Technology and other Research and Development.