Even Deserts are Carbon sinks–DUH

Some are in a tizzy that carbon dioxide stimulation would increase carbon sink effect in arid desert.

I would suggest that makes sense, and that the effect of carbon dioxide on deserts is to increase ground cover.
One thing that struck me as odd about their abstract is they ignored the obvious–water vapor is a much more important green house gas than carbon dioxide.
http://politicalhotwire.com/current-events/103195-who-would-have-guessed-deserts-absorb-immense-amounts-co2.html