Long-term modeling of soil C erosion and sequestration at the small watershed scale

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Climatic Change, 80:73-90

DOI:https://doi.org/10.1007/s10584-006-9167-6· OSTI ID:901167

Izaurralde, R Cesar C; Williams, Jimmy R; Post, W M; Thomson, Allison M; Mcgill, William B; Owens, Lloyd; Lal, Rattan

The soil C balance is determined by the difference between inputs (e.g. litter, crop residues, decaying roots, organic amendments, depositional C) and outputs (e.g. soil respiration, dissolved organic C leaching and eroded C). Two competing hypotheses suggest erosion may either increase or decrease output. One hypothesis states that C from eroded fields becomes “sequestered” in depressional areas and thus is rendered unavailable for decomposition. An alternative hypothesis argues that due to aggregate breakdown during erosion events, physically-protected C becomes accessible, thereby increasing oxidation of C and emission of CO2. This study applied the EPIC (Erosion Productivity Impact Calculator) model to evaluate the role of erosion-deposition processes on the C balance at the small watershed scale. The experimental records of three small watersheds (~1 ha) from the USDA North Appalachian Experimental Watershed facility north of Coshocton, OH were used in the study. Predominant silt loam soils in the area have developed from loess-like deposits over residual bedrock. Soil and crop management in the three watersheds has changed over time. Currently, watershed 118 (W118) is under a corn (Zea mays L.) - soybean (Glycine max (L.) Merr.) no till rotation, W128 is under conventional till continuous corn, and W188 is under no till continuous corn. Predictions of sediment C yields were made through simulation of an entire range of ecosystem processes including plant growth, runoff, and water erosion. A simulated sediment C yield of 39 kg C ha-1 y-1 compared well against an observed value of 31 kg C ha-1 y-1 in W118. EPIC overpredicted the soil C stock in the top 30-cm soil depth in W188 by 21% of the measured value (36.8 Mg C ha-1). Predictions of soil C stocks in the other two watersheds (42.3 Mg C ha-1 in W128 and 50.4 Mg C ha-1 in W188) were off by <1 Mg C ha-1. Although these results do not directly answer any of the two prevailing hypotheses, they do provide insight as to the importance of erosion-deposition processes in the C cycle at the small watershed scale. In future work, the APEX model, the landscape version of EPIC, will be used to study the role of erosion and deposition as sources or sinks of atmospheric C.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 901167
• Report Number(s): PNNL-SA-45368; KP1702020
• Journal Information: Climatic Change, 80:73-90, Journal Name: Climatic Change, 80:73-90
• Country of Publication: United States
• Language: English

Related Subjects

water erosion
soil deposition
sediment carbon
atomospheric carbon dioxide
soil carbon sequestration