Generalized Model for the Temporal Evolution of the Carbon Sequestration Potential of Eroding Watersheds

Carbon (C) balance in dynamic landscapes is significantly influenced by lateral re- distribution of topsoil and associated soil carbon (C) across different landform po- sitions. Over the last two decades, the conceptual and mechanistic basis for how soil erosion can induce a significant terrestrial sink for atmospheric carbon dioxide has been well established. However, we still lack a broadly applicable, but versatile/simple mathematical representation of how soil erosion invokes a C sink in which C input rates to the soil outpace release rates of C in eroding watersheds. This is especially true for systems that experience large erosion events that can quickly lead to large shifts in soil organic matter stock at both eroding slopes and deposi- tional landform positions of the same watershed. Here, we present the mathematical representation for the erosion-induced C sink where an eroding watershed is concep- tualized as being made up of one eroding and one depositional box, and C dynamics is simulated assuming first order kinetics and a one-pool soil C model. This process- based time-evolution analysis is presented to guide empirical field and lab studies in this subject.