Objectives of this research were to determine the effect of altered hydrology on species composition and radial growth of trees in floodplain forests of the Lower Kaskaskia River. The Carlyle Dam caused significant changes in hydrology below the site of installation. Flood frequency and duration at a site 6.4 km below the dam was significantly reduced. Flood frequency was more variable at the site 6.4 km below the dam prior to dam installation. Post-dam flood frequency and duration were related to overstory and midstory species composition for all sites, whereas pre-dam hydrology was not related. This indicates that the current species composition has adjusted to post-dam river hydrology. Medium to high post-dam mean annual flood frequency and flood duration, were related to Acer negundo/Acer saccharinum, Acer saccharinum , and Acer saccharinum/Fraxinus pennsylvanica overstory assemblages. Low to medium post-dam mean annual flood frequency and flood duration were related to Betula nigra/Ulmus americana and Celtis occidentalis overstory assemblages. The overstory stratum could potentially succeed to Celtis occidentalis, a shade tolerant species dominant in the midstory strata if current conditions continue. Increasing % clay was related to Acer negundo/Acer saccharinum, Acer saccharinum , and Acer saccharinum/Fraxinus pennsylvanica overstory assemblages. Increasing % sand was related to Betula nigra/Ulmus americana and Celtis occidentalis overstory assemblages. Soil texture was not significantly related to midstory species composition. Increasing Quercus palustris basal area was related to increasing pre-dam flood duration, and no post-dam Quercus spp. relationships to hydrology were found. Significant relationships of radial growth to flood and climate variables were found, although variables were not always related in the same manner to radial growth. Generally, the relationships of climate and flood factors were different after dam installation than before. The Carlyle Dam has altered hydrology and changed tree species composition and radial growth along the Lower Kaskaskia River. Further research concerning the central floodplain forest is needed at the landscape scale to address the consequences of hydrologic alterations throughout our large river systems.

Of all the outputs of forests, water may be the most important. Streamflow from forests provides two-thirds of the nation's clean water supply. Removing forest cover accelerates the rate that precipitation becomes streamflow; therefore, in some areas, cutting trees causes a temporary increase in the volume of water flowing downstream. This effect has spurred political pressure to cut trees to increase water supply, especially in western states where population is rising. However, cutting trees for water gains is not sustainable: increases in flow rate and volume are typically short-lived, and the practice can ultimately degrade water quality and increase vulnerability to flooding. Forest hydrology, the study of how water flows through forests, can help illuminate the connections between forests and water, but it must advance if it is to deal with today's complexities, including climate change, wildfires, and changing patterns of development and ownership. This book identifies actions that scientists, forest and water managers, and citizens can take to help sustain water resources from forests.

This report is a literature review concerning the impacts of flooding regime modification on bottomland hardwood forest wildlife habitats of the lower Mississippi Valley. Documented effects on forest vegetation and wildlife populations are described. The composition and structure of the bottomland are an important determinant of the quality and type of wildlife habitat available. These forest characteristics are, in turn, largely influenced by the flooding regime. In general, overstory diversity and perennial understory diversity and productivity are lowest in near-permanently flooded habitats and increase in areas flooded less frequently and for shorter periods of time. Nonflooded areas are often, but not always, less diverse and productive than infrequently flooded areas. A permanent change in flooding regime is likely to cause a gradual change in composition and structure, resulting in forest characteristics similar to those normally found under such hydrologic conditions. Tree growth, regional habitat diversity, and land clearance patterns may also be influenced by modifications to the hydrologic regime.