Characterization of Soil Processes in Bottomland Hardwood Wetland-NonwetlandTransition Zones in the Lower Mississippi River Valley

摘要

This document reports results of a 4-year study of bottomland hardwood soils.Study purposes were to characterize the effects of saturation and inundation on soil processes in nonwetland, transitional, and wetland to provide data for identifying and delineating wetlands from nonwetlands in the Lower Mississippi River Valley. Detailed technical information for constructing and installing equipment to measure soil redox potential and oxygen content is provided. Soil redox potential, oxygen, content, and water table depth were measured at several soil depths on five transects in Louisiana and Mississippi. These data were compared with soil profile descriptions, hydrologic zonal classification, and the presence of hydric soils to determine relationship among soil redox conditions and diagnostic wetland indicators. Tree-coating constituents were also measured to determine if plant adaptations are effective indicators of wetland soil conditions. Results indicated that large areas of bottomland hardwood forests in the Lower Mississippi River Valley are not inundated or saturated for long periods during the growing season. There are very wet, almost permanently inundated sites, but those areas that are seasonally inundated are oxidized and aerobic throughout the root zone for most of the growing season. Saturated, anaerobic conditions for as little as 10-15% of the the growing season appear sufficient to induce wetland soil characteristics (mottling, gleying, low chroma colors) in the soil profile. These wetland soil characteristics were generally more reliable than the plant root coatings in delineating wetlands.