Within the past century modifications to Southeastern US river systems for navigation and flood control have permanently altered the natural hydrologic and geomorphic processes of most bottomland hardwood forest (BLH) floodplains. Some BLH ecosystems are subsequently exhibiting a transition from hydric to more mesic tree species communities, a transition possibly driven by mechanisms within the regeneration process. The purpose of this study was to evaluate the phenology of BLH tree species regeneration and to identify the effects of hydrologic patterns on BLH recruitment. We established 155 1 x 1 m plots in the floodplains of two wildlife management areas (WMAs) in northern Louisiana where we are monitoring seedling emergence, growth, and survival for the 2016-2018 growing seasons. We also established five groundwater monitoring wells in the WMAs to collect long term data on surface and groundwater patterns.
Results/Conclusions
During the 2016 growing season, we documented 1737 individual seedlings among 19 species; in 2017 we documented an additional 515 new seedlings among 12 species. The most abundant seedling was swamp privet (Forestiera acuminata) with 1069 seedlings, followed by American elm (Ulmus americana; n=470), overcup oak (Quercus lyrata; n=102) and water elm (Planera aquatic; n=101). Seedlings at the least flooded or non-flooded sites were dominated by American elm, green ash (Fraxinus pennsylvanica; n=86), and sugarberry (Celtis laevigata; n=61), most of which emerged from early May through early June. In contrast, seedlings at the more flooded sites generally emerged from June through August; these sites were dominated by overcup oak, water elm, swamp privet, willow oak (Quercus phellos; n=-49), and Nuttall oak (Quercus texana; n=21). Not all species were present at every site, and though there was some overlap between groups of species, data collection remains ongoing to evaluate discrepancies between sites.