Modeling Carbon Dynamics

Summer 2004

As the main building block of life, carbon anchors all organic things, from DNA to fossil fuels. But carbon is not necessarily fixed; it moves through the land, ocean, and atmosphere.

In fact, forces such as soil erosion and soil deposition can influence the exchange of carbon between terrestrial ecosystems and the atmosphere.

To better understand these movements, SAIC researchers Shuguang Liu and Norman Bliss have developed a model (Erosion-Deposition-Carbon-Model) that simulates the effects of rainfall-induced soil erosion and deposition on the dynamics of soil organic carbon. (Their research used data compiled from a farm in Tate County, Mississippi, which had been converted to agriculture from forest land around 1870.)

In their ESTC award-winning paper, Liu and Bliss show that soil erosion and deposition tend to reduce carbon dioxide (CO2) emissions from the soil into the atmosphere. (CO2 is released into the atmosphere through the respiration of soil organisms feeding on plant material.)

This reduction occurs by exposing low carbon soil at eroding sites and by burying high carbon-containing soil at sites of deposition. Moreover, eroded carbon buried in wetlands and water bodies can further contribute to reducing the rates of increase of atmospheric carbon dioxide. (In contrast, when forests are cleared for agriculture, some carbon in living material and soil is released, causing atmospheric CO2 concentrations to increase.)

Liu and Bliss do not want to imply that soil erosion and soil deposition on croplands are beneficial to the environment. Indeed, they stress that these forces decrease site fertility, contribute to nonpoint pollution, and reduce the efficiency and life expectancy of waterways and reservoirs. Rather, the researchers suggest that failing to account for the impact of soil erosion and deposition may contribute to an overestimation of the total historical carbon released from soils because of land usage.

Liu and Bliss' paper, "Modeling Carbon Dynamics in Vegetation and Soil under the Impact of Soil Erosion and Deposition," appeared in Global Biogeochemical Cycles.

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