The Upper Mississippi River floodscape: spatial patterns of flood inundation and associated plant community distributions

Questions: How is the distribution of different plant communities associated with patterns of flood inundation across a large floodplain landscape? Location: Thirty-eight thousand nine hundred and seventy hectare of floodplain, spanning 320 km of the Upper Mississippi River (UMR). Methods: High-resolution elevation data (Lidar) and 30 yr of daily river stage data were integrated to produce a 'floodscape' map of growing season flood inundation duration. The distributions of 16 different remotely sensed plant communities were quantified along the gradient of flood duration. Results: Models fitted to the cumulative frequency of occurrence of different vegetation types as a function of flood duration showed that most types exist along a continuum of flood-related occurrence. The diversity of community types was greatest at high elevations (0-10 d of flooding), where both upland and lowland community types were found, as well as at very low elevations (70-180 d of flooding), where a variety of lowland herbaceous communities were found. Intermediate elevations (20-60 d of flooding) tended to be dominated by floodplain forest and had the lowest diversity of community types. Conclusions: Although variation in flood inundation is often considered to be the main driver of spatial patterns in floodplain plant communities, few studies have quantified flood-vegetation relationships at broad scales. Our results can be used to identify targets for restoration of historical hydrological regimes or better anticipate hydro-ecological effects of climate change at broad scales.