Organic carbon storage in floodplain soils of the U.S. prairies

Abstract

Two data sources, field‐collected samples and values in the NRCS SSURGO database, were used to estimate organic carbon concentration (%) and stock (Mg C/ha) in floodplain soils along rivers of the tallgrass and shortgrass prairie within the United States. Field sampling of 6 sites in the tallgrass prairie and 6 sites in the shortgrass prairie (total sample size of 370 vertical cores) indicates that percent organic carbon within a planar cross section through floodplain sediment at a site is spatially heterogeneous and does not decline systematically with depth, but statistical analyses indicate that soil organic carbon is randomly distributed. The median values of organic carbon concentration at both field‐sampled and sites remotely sampled based on soil maps in the tallgrass prairie are significantly higher than those of the shortgrass prairie. Median values of organic carbon stock are not significantly different between those obtained from forested sites for comparison and either shortgrass or tallgrass prairie sites but are significantly higher at tallgrass than at shortgrass prairie sites. These results are surprising because upland net primary productivity in prairies is lower than in forested sites. We infer that the historical abundance of floodplain wetlands in river corridors of the tallgrass prairie results in high organic carbon stocks in tallgrass prairie river corridors. This implies that management designed to enhance carbon sequestration should focus on floodplain soils, especially in the tallgrass prairie region, as well as on upland forests.

Quantitatively Estimating Carbon Sequestration Potential in Soil and Large Wood in the Context of River Restoration

“…Existing databases can also be used to estimate floodplain carbon stock semi-quantitatively. Soil maps, including those available for much of the United States through the SSURGO online database (Soil Survey Staff, 2021), provide representative values for soil texture with depth, total organic carbon, bulk density, and soil thickness for a soil series, and these parameters can be used to calculate soil organic carbon stock (e.g., Wohl and Pfeiffer, 2018). Existing databases for large wood are largely nonexistent, although regional case studies that quantify expected wood loads based on position in the river network or channel width are available for a few locations, such as Washington State in the United States (Fox and Bolton, 2007).…”

Geomorphic regulation of floodplain soil organic carbon concentration in watersheds of the Rocky and Cascade Mountains, USA

“…In the context of the carbon cycle, floodplains can act as a major component of the biospheric carbon pool (Aufdenkampe et al, 2011;Battin et al, 2009). Floodplain soils can act as a substantial pool of OC despite their relatively small aerial extent, indicating that floodplains may be disproportionately important compared to uplands in terms of carbon storage (D'Elia et al, 2017;Hanberry et al, 2015;Sutfin et al, 2016;Sutfin and Wohl, 2017;Wohl et al, 2012Wohl et al, , 2017a. Mountainous regions, due to their high primary productivity (Schimel and Braswell, 2005;Sun et al, 2004), may play a substantial role in the freshwater processing and storage of OC whereby they retain sediment and water along the river network (Wohl et al, 2017b).…”

Recognizing the ephemeral stream floodplain: Identification and importance of flood zones in drylands

“…Dry streams and floodplains account for approximately 4.4[0.4–9]% (0.08 [0.01–0.17] Pg year −1 C) of CO 2 emissions from watercourses globally but over 50% of CO 2 emissions from watercourses in drylands (von Schiller et al, 2017). However, ephemeral stream floodplains can also store carbon in their soils (Harms & Grimm, 2012; Wohl & Pfeiffer, 2018) and in surficial deposits of large wood and coarse particulate organic matter (Wohl & Scamardo, 2022). Antecedent moisture can suppress the activity of microorganisms that moderate gas emission from ephemeral stream floodplains, so that successive floods during the wet season are less likely to cause a large gas emission compared with individual flows during the dry season (Harms & Grimm, 2012).…”