COMPARISON OF SEDIMENTATION AND LEAF LITTER DECOMPOSITION RATES AMONG MODIFIED 
RIVER FLOODPLAIN SYSTEMS IN THE LOWER MISSISSIPPI ALLUVIAL VALLEY.

Mehdi Molavi and Jack W. Grubaugh
Department of Biology, University of Memphis, Memphis, TN 38152.

River floodplain systems of the lower Mississippi Alluvial Valley (LMAV) have 
been modified extensively through channelization and levee construction to 
facilitate human activities. These impacts potentially influence floodplain 
ecosystem functions such as leaf litter decomposition. Sediment accumulation and 
leaf litter decomposition rates were determined in floodplain habitats along six 
differentially impacted river systems (two "unimpacted," two channelized, and 
two channelized/leveed) in western Tennessee. 
Decomposition rates varied significantly with litter type (Drummond's red 
maple>site-specific leaf litter>water oak). Sediment accumulation rates differed 
among treatments, with highest accumulation occurring in "unimpacted" systems 
and lowest in channelized/leveed systems. Depressional areas of the floodplain 
exhibited significantly lower sedimentation rates than non-depressional areas, 
suggesting depressional sites are maintained by scouring. Additionally, 
decomposition rates were significantly and negatively correlated to sediment 
accumulation rates. These results indicate that sedimentation is a controlling 
factor of leaf litter decomposition in floodplains of the LMAV, regardless of 
source or type of anthropogenic modification.

Keywords: Drummond's red maple, water oak, channelized and leveed, lower 
Mississippi Alluvial Valley, leaf litter decomposition