Seasonal and Longitudinal Variations in Suspended Load Connectivity Between River Channels and their Margins

Input of organic matter into stream channels is the primary energy source for headwater ecosystems and ultimately carbon to oceans hence an important component global cycle. Here, we quantify organic-rich fine sediment mobilization, transport, storage in a Strahler fourth-order during individual intermediate-sized storm events. By combining measurements fallout radionuclides (FRNs) 7Be 210Pb stable water isotopes with conceptual model suspended load trapping by channel margins, find that bed was consistently margins. Relative on export increased through spring summer, perhaps related in-channel decomposition debris as indicated its FRN exposure age changing bulk δ13C composition. Trapping riparian margins limits transport distances, which, given sufficient discharge fully suspend load, nearly independent sub-bankfull discharges. Limited data indicate fractional size where occurs decreases increasing watershed area. Increasing length decreasing margin area results systematic downstream decoupling from local terrestrial exchange. These findings provide framework understanding dynamics formerly glaciated regions production fluxes are generally low thus annual input major budget.