OOS 32-4 - How important is molecular structure for the decomposition of soil organic matter?

Wednesday, August 8, 2012: 2:30 PM
B113, Oregon Convention Center
Markus Kleber, Department of Crop and Soil Science, Oregon State University, Corvallis, OR

A long tradition of soil organic matter research has generated the belief that there is “stable” soil organic carbon, thought to be recalcitrant because molecular compounds such as aromatic rings and aliphatic chains are joined to polymeric macromolecules by processes of secondary syntheses. The Carbon-Quality Temperature (CQT) theory posits that such materials are “low quality” substrates, because they require large Arrhenius activation energies for full conversion to CO2.
The (supposed) requirement of greater activation energies has generated the notion that the decomposition of "low quality" = "recalcitrant" organic compounds should be more sensitive to elevated temperatures than the decomposition of less complex, more “labile”  compounds . 


In this contribution I review and examine the role of molecular structure (aka "soil organic matter quality" or "inherent recalcitrance") for soil organic matter decomposition. I will attempt to provide answers to the questions: How does molecular structure of soil organic matter factor in the complex chain of events that convert reduced soil carbon to CO2? and: How important is perceived "recalcitrance" of organic carbon for the temperature sensitivity of soil organic matter decomposition ?