Soil carbon saturation: a new model of soil organic matter stabilization and turnover

Stewart, Catherine E., author
Paustian, Keith H., advisor
Six, Johan, committee member
Conant, Richard T., committee member
Sutton, Sally, committee member
Journal Title
Journal ISSN
Volume Title
The soil C saturation concept suggests an ultimate capacity of the soil to store C, dictating the rate and duration that soil may be effective in mitigating increasing atmospheric C02. This places a physicochemical limit on soil that is associated with textural, mineralogical and structural soil properties. This concept has been articulated in terms of four theoretical pools capable of C saturation: non-protected, physically- (micro-aggregate), chemically- (silt + clay), and biochemically-protected pools. My dissertation represents a multifaceted approach to examine C saturation in both whole soil and measurable soil fractions representing the four conceptual C pools. I evaluate the soil C saturation concept theoretically by modeling these relationships using published whole soil data, primary field data and through laboratory experiments. Analyses using published long-term soil C data from agroecosystem experiments suggested that within a given site, there was little support for models including C saturation, but when all sites were combined; there was strong support for the C saturation model. In general, published data were too sparse to adequately test individual sites. To evaluate the concept of C saturation for the four C pools, I used a three-part density, chemical, and physical fractionation scheme combined with modeling, using new data collected from eight agroecosystems in the US and Canada. I found that the chemically- and biochemically-protected pools showed strong evidence for C saturation, while the non-protected and physically-protected pools were non-saturating. In a 2.5 year laboratory experiment, I tested C stabilization rates and limits at two C addition rate to soils differing in soil C content and physicochemical characteristics. I found C saturation dynamics were most evident in the chemically-, biochemically- and some micro-aggregate protected C pools. I found greater C accumulation in the non-protected pool of the high C soil, suggesting C saturation of other pools. I conclude that SOC sequestration in many soils may be influenced by C saturation dynamics, impacting both decomposition kinetics and C stabilization. Soil C sequestration may be overestimated in models that do not account for C saturation dynamics.
2006 Spring.
Includes bibliographical references.
Rights Access
Soils -- Carbon content
Atmospheric carbon dioxide
Associated Publications