Floodplains are among the world’s economically-most-valuable,environmentally-most-threatened, and yet conceptually-least-understood ecosystems. Drawing on concepts from existing riverine and wetland models, and empirical data from floodplains of Atlantic Coast rivers in the Southeastern US (and elsewhere when possible),we introduce a conceptual model to interpret a continuum of longitudinal variation in floodplain ecosystem functions with a specific focus on biotic change. Our hypothesis maintains that major controls on floodplain ecology are either external (ecotonal interactions with uplands or stream/river channels) or internal (wetland-specific functions), and the relative importance of these controls changes progressively from headwater to mid-river to lower-river floodplains. Inputs of water, and sediments,nutrients, flora, and fauna from uplands-to-floodplains decrease,while the impacts of wetland biogeochemistry and obligate wetland plants and animals within-floodplains increase, along the length of a river floodplain. Inputs of water, or sediment,nutrients, and fauna from river/stream channels to floodplains are greatest mid-river, or lower either up- or down-stream. While the floodplain continuum we develop is regional in scope,we review how aspects may apply more broadly. Management of coupled floodplain-river ecosystems would be improved by accounting for how factors controlling the floodplain ecosystem progressively change along longitudinal riverine gradients.
Source: usgs.gov