Dosing vodka or vinegar will consume alkalinity for a short period of time because an organic acid is formed. As the organic acid is consumed, the alkalinity will be released. I suspect other carbon sources could produce organic acids, as well.
As nitrate is consumed, alkalinity will be released. This article discusses alkalinity in the nitrogen cycle.
http://reefkeeping.com/issues/2004-12/rhf/index.htm
The theory behind carbon dosing is that some of the biomass is exported via skimming. That's very difficult to prove or quantify, but carbon dosing does seem to work very will in many systems.