Can someone provide good references on grasslands and carbon sequestration?

I've been asking the same question.  Everyone at TNC seems to be focused on forests as carbon sinks, so I've had trouble getting references.  Recently, I Googled "grasslands carbon sequestion" and got a number of very interesting and encouraging references.  I'm in the process of checking them out with Joe Fargione the CUSCR Regional Scientist and others.  I'll let you know what I hear.  Let me know if you hear from others.  This could be the strongest case for global grassland conservation that has come along to date.