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A Floodplain Continuum for Atlantic Coast Rivers of the Southeastern US: Predictable Changes in Floodplain Biota along a River’s Length

Batzer, DaroldP., Noe, GregoryB., Lee, Linda, Galatowitsch, Mark
Wetlands 2018 v.38 no.1 pp. 1-13
animals, biogeochemistry, coasts, ecological function, ecosystems, fauna, floodplains, flora, highlands, models, nutrients, rivers, sediments, stream channels, water, wetland plants, wetlands, Southeastern United States
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 explain a continuum of longitudinal variation in floodplain ecosystem functions with a particular 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, 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, sediment, nutrients, and fauna from river/stream channels to floodplains are greatest mid-river, and 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.