My former postdoc turned Assistant Professor, Marie Anne de Graaff, just had a new paper come out in Soil Biology and Biogeochemistry (DeGraaff_SBB_InPress). In it we were able to further explore the favorite topic of our research, namely how plant root processes and properties influence soil biogeochemistry and microbial communities/processes. While many scientists and laypeople alike have been interested in harnessing the amazing productivity of switchgrass for cellulosic biofuels for some time, not as many may appreciate that this incredible productivity takes place not only in the harvestable aboveground tissue, but also extends belowground to the root systems! Switchgrass can send roots meters deep into the soil year after year due to its perennial nature, and in doing so may increase soil carbon storage (or sequestration) over more conventional annual crops. Switchgrass exists in many varieties which have primarily been explored and exploited for their productivity under various potential cropping regimes for biofuel feedstock production. In this paper we explored the potential for varietal differences in root production and properties to effect their own decomposition rates and also how this in turn may influence soil organic carbon turnover (e.g. priming).
The results were fairly impressive. As you can see above, even with the naked eye, differences in root properties can be fairly striking. Varieties show differences in the amount of material invested in fine (smaller) roots vs. coarser (larger) roots. These differences in turn have effects on how fast the roots decompose, and how much they ‘prime’ the decomposition of resident soil organic carbon. While the experiments were done in laboratory incubations so its hard to directly translate to in farma results, it certainly argues for further consideration of belowground properties of these crops in future applied ag research. Consideration not only of their aboveground potential for ethanol, but perhaps the value of switchgrass crops on the carbon offset market could result, with a greater understanding of the role of switchgrass in increasing soil carbon storage.
Marie Anne had a very productive postodoc while here at ORNL for which I can take very little credit. She came into our lab already motivated and well prepared, got right to work with multiple experiments and was able to move results from the lab to papers amazingly efficiently. This recent paper represents some of the last work she initiated here at ORNL and then was able to finish up in her new position at BSU. We are continuing this kind of research in my lab in various projects and collaborations (including this one with Professor de Graaff)
A few fun photos from past work!
Hydroponically Grown Switchgrass (photo from Chuck Garten)
Cutting Alleys for us to get to some switchgrass plots in Milan, TN in 2007 (photo from Robin Graham)