This post got me thinking about the research paper.  I must confess I didn't read it.  But if they chose a field that wasn't long-term no-till, the microbial population would be different.  Many no-tillers have noticed that early on in the adoption of no-till, their mulch cover stays around for awhile.  After a few years, it seems like you just can't keep the mulch anywhere near as long -- which is a concern in warmer climates.  The microbial population has shifted, and is quite a 'digester.'  This *might* explain some of the results of the research paper.  Pure conjecture, here.