Stabilization and destabilization of soil organic matter—a new focus

Interest in soil organic matter (SOM) is ramping up as concern mounts about steadily increasing levels of atmospheric CO2. There are two reasons for this. First, there is hope that improvements in crop, forest, and soil management may allow significant amounts of CO2 to be removed from the atmosphere and sequestered in soil. Second is the possibility that increased soil respiration rates, associated with climate change, will unleash a positive feedback in which temperatures rise even faster than now expected. Other reasons have long existed for understanding SOM dynamics, such as SOM as the source of most of the nonfertilizer N needed for plant growth, but the specter of run-away climate change seems to have now overtaken these other justifications. Much of the work on SOM triggered by climate change has involved measuring pools over large areas and, especially, changes in those pools over time (Smith 2004; Bellamy et al. 2005). Other work has sought to measure changes in soil C and N stores under elevated CO2 regimes (Lin et al. 1999; Six et al. 2001; Jastrow et al. 2005). But it is widely recognized that measuring such changes is not enough. We have to understand the mechanisms underlying soil organic matter stabilization if we are to predict the course of CO2 flux between atmosphere and soil under a changing climate and a steadily increasing demand for agricultural and forest products. A 6-year project led by Prof. Ingrid KögelKnabner (Soils as Source and Sink for CO2—Mechanisms and Regulation of Organic Matter Stabilization in Soils, funded by Deutsche Forschungsgemeinschaft) was arguably the first major formal effort in this direction. The project also hosted the First International Conference on Mechanisms of Soil Organic Matter Stabilization as part of a mid-term project review. The conference (Munich, October 2003) was attended by about 140 people from 12 countries. Several American SOM scientists asked if a follow-up conference in the US was warranted. The response was enthusiastic and funding was secured from US sources including the National P. Sollins (&) Forest Science Department, Oregon State University, Corvallis, OR 97331, USA e-mail: [email protected]