Organic Carbon Storage in Rivers in the United States – Ellen Wohl
As part of a national-scale inventory of organic carbon stored along river corridors in the United States, we are measuring the organic carbon content of floodplain soils along rivers of the tallgrass and shortgrass prairies, shown below:
Several studies suggest that floodplain organic carbon (OC) stocks represent globally significant reservoirs of OC that can remain in storage for timespans of 103-104 years, but numerous questions remain regarding the inputs, storage, and exports of OC from river corridors. The primary objective of this research is to examine how the potential control variables of time since deglaciation and ecosystem engineering by beaver influence the spatial distribution and magnitude of organic carbon stocks and fluvial export. The secondary objectives are to use a stratified random sampling design to quantify OC stocks (Mg C/ha) in the form of downed large wood and floodplain soil OC; quantify OC export in the form of dissolved and particulate OC and large wood; and relate OC stocks and export to hillslope and channel processes and potential control variables, including forest stand age and species composition, hillslope stability, valley geometry, channel planform, discharge of water and suspended sediment, and time since deglaciation. Starting in Summer 2020, we will address these objectives by sampling soil and dead wood OC throughout two watersheds, the Rio Exploradores of Chilean Patagonia and the Stehekin River of the U.S. northern Cascade Range. We will use a multi-stage sampling technique by first delineating the basin into strata based on drainage area, then by valley lateral confinement within each drainage area stratum. Within each valley confinement stratum, we will (i) take a simple random sample of points across the floodplain of the river and sample the soil to a maximum depth of 1 m at each point and (ii) randomly select reaches ~ 10 channel widths in length to sample for instream and floodplain wood volume.