FLOODING AND FOREST SUCCESSION IN A MODIFIED STRETCH ALONG THE UPPER MISSISSIPPI RIVER

This research examines the effect of a rare flood on floodplain forest regeneration in a 102-km stretch of the Mississippi River beginning 2 1 km above the mouth of the Ohio River. The river has been restricted by levees and navigation structures and subjected to sediment dredging to maintain a stable navigation channel. Because the bank erosion-acc retion process has been slowed or eliminated, cottonwood (Populus spp. ) and willow (Salix spp.) communities regenerate poorly in the modifie d river environment. An unusually large flood in 1993 destroyed the en tire ground vegetation layer, killing 77.2% of the saplings and 32.2% of the trees. The flood created an alternative mechanism for cottonwoo d and willow to regenerate under canopy openings, enabling the communi ty type composition of the present-day forest to be sustained for the next 50 years. Over time, however, the forest will likely exhibit cons iderable compositional fluctuation. (C) 1998 John Wiley & Sons, Ltd.