Consortium for Research on Enhancing Carbon Sequestration in Terrestrial Ecosystems (CSiTE)

Julie Jastrow, Argonne contact (jdjastrow@anl.gov)

CSiTE conducts research to provide the understanding required to develop successful approaches for enhancing belowground carbon sequestration in terrestrial ecosystems as a partial mitigation of CO2-induced climate change.  CSiTE research is integrated across Argonne, Oak Ridge, and Pacific Northwest National Laboratories and several partnered universities.  CSiTE addresses the following research and development needs at multiple scales:  (1) What are the physical, biological, and chemical processes controlling soil carbon input, distribution, and longevity? (2) How can these processes be exploited to enhance terrestrial carbon sequestration? (3) How do terrestrial carbon sequestration strategies relate to and influence other strategies to mitigate climate change? (4) What is the long-term potential for terrestrial carbon sequestration to mitigate climate change at a global scale?  These needs are addressed by developing (1) laboratory and field research to elucidate the mechanisms and processes that control soil carbon inputs and the distribution and longevity of soil carbon; and (2) conceptual and computational models for extrapolation of process understanding across space and time.
 

To facilitate investigation of the mechanisms and processes promoting sustained terrestrial carbon sequestration, initial CSiTE research focused on existing field sites with long-term manipulations expected to be accumulating carbon – such as the chronosequence of prairie restorations at the Department of Energy’s Fermilab National Environmental Research Park in northeastern Illinois.  Disturbance associated with long-term cultivation of soils releases large amounts of stored soil organic matter as CO2 to the atmosphere.  Restoration of degraded soils and ecosystems can be a major strategy for reversing soil organic matter losses and enhancing soil carbon sequestration.  In our studies using both a chronosequence approach and repeated sampling of restored tallgrass prairies at Fermilab, we found sustained carbon accrual rates of 0.4 Mg C ha‑1 yr‑1 over a period of 26 years in surface soils typical of the Corn Belt Region.  Estimates based on comparison of agricultural soils to native prairie remnants suggest these soils have a carbon storage potential of about 35 Mg C ha-1 and chronosequence modeling predicts that 50% of this potential can be reached in 100 years.  Most of the accumulated soil carbon is derived from turnover of the extensive prairie root system; however, our studies of soil microbial communities have found that mycorrhizal fungi contribute an average of 5% of the carbon inputs to soil organic matter with greater proportions occurring during the initial years of restoration.  In addition, analysis of repeated samples collected over a period of 19 years from several prairie plots and grassland dominated by smooth brome (a cool-season, Eurasian pasture grass) revealed that more carbon has been sequestered under prairie than under brome and that sequestration rates under prairie are affected by soil hydrologic conditions.  Our results demonstrate that restoration of tallgrass prairie vegetation can rapidly restore soil organic carbon lost from surface soils through cultivation and has the potential to sequester relatively large amounts of carbon in the soil over decadal time scales.

In 2007, CSiTE reorganized around seven scientific themes (see diagram) and coordinated its research activities around existing and planned field experiments with switchgrass (Panicum virgatum) and other bioenergy crops.  The overarching hypothesis is that simultaneous biofuel feedstock production and enhancement of soil carbon sequestration are sustainable.  The use of bioenergy crop production as our test bed to study terrestrial carbon sequestration in an intensive, vertically integrated study will give our findings immediate application to the development of an important energy technology, in addition to advancing terrestrial carbon sequestration technologies.

Our role in CSiTE’s integrated switchgrass experiments includes a variety of tasks.  We are measuring net ecosystem production, and we are involved in quantifying belowground carbon inputs, their initial transformation to soil organic matter, and the traits of roots and associated mycorrhizal fungi that lead to greater and longer carbon sequestration.  We are also investigating physicochemical mechanisms of soil organic matter stabilization and the potential for saturation of these mechanisms on soil carbon sequestration.  In addition, we are studying how changes in the abundance and activity of functional groups of soil microbes affect soil carbon sequestration.

Links
CSiTE web page:  http://csite.ornl.gov/
Fermilab prairie restorations:  http://www.fnal.gov/pub/about/campus/ecology/index.html