Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA

► We examined floodplain forest vegetation and soils across a flood duration gradient. ► Soils trended toward silt/clay and >5% OM from 0% to ∼40% of the growing season flooded. ► Tree diversity declined from 0% to ∼40% of the growing season flooded. ► Uniformly high silt/clay and OM and low tree diversities were found >40% flooded. ► Flooding exerts primary control over soils and trees where inundation >∼40% flooded.