Less than 40% of the once vast bottomland hardwood forest (BLH) ecosystem in the southeastern US remains, due to conversion to agriculture and urban expansion. Today, most remnants are second and third-growth with precious few old-growth and mature forests remaining in the landscape. The mature remnants often differ markedly from their young counterparts and are highly valuable as references to guide ongoing restoration efforts. Our primary aim was to summarize the ecological and physical attributes of exemplary old-growth and mature BLH forests for comparison with younger floodplain forest examples from the literature. Our secondary objective was to assess threats to these remnants, along with current management strategies and opportunities. We identified and selected four mature forest study sites that span the historic distribution of BLH: Congaree Swamp National Park in central South Carolina, Four Holes Swamp in coastal South Carolina, Jean Lafitte National Historical Park and Preserve in coastal Louisiana, and the Cache River Natural Area in southern Illinois.
Results/Conclusions
Although they make up a relatively small portion of the landscape compared to their upland counterparts, mature and healthy BLH forests, particularly ones with seasonal flooding and flow, have high productivity. They provide habitat for wildlife and numerous other species and are thus critical for supporting regional biodiversity. Mature BLH forests are also responsible for the provisioning of many ecosystem goods and services, including flood control, maintenance of water quality, and nursery habitat for commercial fisheries, to name a few. Despite their greater functionality compared to younger forests, they are often embedded in a highly modified landscape and thus vulnerable to effects of surrounding land use changes and hydrologic alterations. The very conditions that support high native biodiversity make BLH forests also susceptible to spread of exotic species. In coastal areas, freshwater floodplains are further eroded by chronic sea level rise and saline storm surges. Hydrologic restoration, control of exotics, and connection of fragments to each other and to migration corridors are key steps for conservation of mature remnant forests and resurrection of the greater BLH ecosystem.