Abundant reed canary grass precludes successful floodplain tree seedling germination. The establishment of reed canary grass (Phalaris arundinacea), which is extremely aggressive and difficult to control, has increased dramatically over the past 15 years in the Upper Mississippi River floodplain forest ecosystem. Since the Upper Mississippi River floodplain forest is a key migratory route for waterfowl and forest interior bird species it is important to understand the extent to which reed canary grass is impacting this system, the key variables that contribute to the success and spread of reed canary grass in these forests, and how these variables can inform management and restoration decisions. This study examined the extent cover of reed canary grass and the correlation between reed canary grass extent and canopy openness, stand age, and percent shoreline in lock and dam pools three through nine of the Upper Mississippi River floodplain forest. We analyzed data gathered between 1995 and 2006 from 2603 U.S. Army Corps of Engineer forest stands. 20m x 20m plots were located every 20m within each stand for a total of 1 to 20 plots/stand depending on stand area. Dominant over and understory species, tree age, dbh, and basal area were recorded in all plots.
Results/Conclusions Floodplain forest dominated by silver maple and emergent marsh dominated by river bulrush occupy large portions of the study area. Much of the current floodplain forest is even-aged, between 50 and 70 years old, and dominated by silver maple. Of the 8243 hectares surveyed, reed canary grass was one of the three most dominant understory species (based on an ocular estimate of frequency) in 48% of plots surveyed. Preliminary analysis indicates that reed canary grass dominance was negatively correlated with canopy closure r = -.637 and positively correlated with percent shoreline r = .453 based on Pearson’s correlation. Moreover these initial results indicate that variables such as available light and edge may create opportunities for reed canary grass to invade and dominate floodplain forest sites expanding out from the initial invasion site. Since much of the canopy in the forests currently not highly impacted by reed canary grass will die back with in the next 50 to 70 years (based on stand age) it is important to develop management and restoration scenarios that incorporate techniques that minimize canopy openings and buffer the shoreline.
