Landscape ecosystem diversity of river floodplains in northwestern Lower Michigan, U.S.A.

We present a classification and comparison of river floodplains using an ecological, multifactor approach integrating physiography, hydrology, soil, and vegetation within a relatively homogenous macroclimate. Aerial photographs and field reconnaissance were used to locate 22 river valley transects along nine major rivers in the Manistee National Forest, northwestern Lower Michigan. Distinct ecosystems along each transect were sampled extensively. Twenty-three floodplain ecosystem types were identified and classified primarily on the basis of physiographic systems and fluvial landforms within a regional context. Physiographic systems are broad-scale, surficial landforms characterized by distinctive form, parent material, soil, hydrologic regimes, and vegetation. We examined landscape ecosystem differences between different physiographic systems, within a physiographic system, and on a single fluvial landform. Different physiographic systems have different kinds and patterns of floodplain ecosystems in successive valley segments along a river. Within a physiographic system, the physiographic position of different fluvial landforms and ecosystem types within a single fluvial landform leads to marked ecosystem diversity laterally away from the river. The results indicate that physiography is an important determinant of floodplain ecosystem diversity and that an ecological, multifactor approach is useful in distinguishing floodplain ecosystems at multiple scales within a regional context.