Channelization, levee construction and floodplain drainage have altered many riverine and small stream systems within MLRA 134 (Southern Mississippi Valley Loess) over the past 100 years. These modifications have the potential to drastically change the ecosystem and impact the functions of the floodplain. Studies have examined these effects in floodplains but there is limited research specific to local landforms. The objective of this study was to compare woody vegetation using plot-based methods in both altered and unaltered sites for three different floodplain landforms (alluvial flat, levee, and poorly drained backswamp/slough) in MLRA 134. Six different riverine systems of varying altered status (channelized vs. non-channelized) were selected for sampling. A 200 m transect was established at each site, and three 15 x 15 m plots were randomly placed along each transect. Canopy cover was measured in each plot using a densiometer. The identity and height of all woody plants over 60 cm tall was determined and richness and species densities were calculated within each plot. Diameter at breast height was measured for trees taller than 1.5 m and total basal area per plot was determined. A PCA was used to compare species composition between the different treatments.
Results/Conclusions
Preliminary data showed differences in community properties between landform types and suggested that channelization has impacted some of these properties within some of the sites. Canopy cover was similar amongst all sites except the unaltered alluvial flat which had higher canopy cover. Poorly drained sites differed the most in composition when compared to other landform sites. In addition, the composition of the non-channelized slough differed from the channelized backswamp. Although there were differences in species richness between the three landform types, with poorly drained sites the lowest and alluvial flats the highest, altering the floodplain hydrodynamics did not appear to have affected richness within landform type. Total basal area was lowest in backswamps/sloughs, regardless of altered status; however these poorly drained landforms had similar tree densities when compared to most of the other sites. The highest total basal area and highest tree densities occurred within one of the channelized alluvial flats. Further examination will determine if soil properties have been altered in these riverine systems leading to changes in the vegetative community structure. Using an ecosystem approach to examine how altering streams and drainage systems affects the environment may subsequently help guide management decisions in these riverine systems.