The interactions of carbon with soil ecosystems are essential to understanding the mechanisms of soil carbon sequestration.  Carbon sequestration through agricultural ecosystems may be a prominent factor in the mitigation of climate change, as it is capable not only of offsetting emissions produced by the agricultural sector, but also of offsetting other emission sources.  Storing carbon in organic form has secondary benefits in that soil organic carbon (SOC) improves soil structure, quality and fertility, as well as improving water quality and preventing erosion (Lal, 2004).

 

Carbon mineralization by microorganisms is responsible for the release of co2 from soils, and is affected by factors such as the climactic conditions, the quality and composition of organic matter, the interaction with soil chemistry, and the location of organic matter in the soil (Jastrow and Miller, 1997).  The rate of mineralization affects the length of time that carbon can be stored in organic form, thus influencing the duration of carbon sequestration.  The three primary mechanisms responsible for  long term organic matter stabilization are biochemical recalcitrance, chemical stabilization and physical protection.

 

Physical protection of organic matter is directly tied to the structure and aggregation of soils. Aggregate sizes are classified by diameter where aggregates >2000 um are considered large macroaggregates; 2000-250 um, are small macroaggregates; 250- 53 um, are classified as microaggregates; and less than 53 um, are silt-sized microaggregates and silt and clay particles (Denef, 2004). Larger aggregates contain more SOC however this carbon content is more labile than in microaggregates, due to a lack of chemical stabilization properties like that which is found in microaggregates  and clay particles(Jastrow and Miller, 1997). Additionally, SOC in macroaggregates is more vulnerable to breakdown as macroaggregates are water soluble and subject to physical disturbance, thus soil management practices greatly impact aggregate size and therefore SOC.

 

  This study examined the relation between microbial breakdown of organic carbon as it was affected by aggregate size, and attempted to determine if tillage and cropping practices held an influence on this process.