Xu et al. 2009

Xu C, Guo L, Ping C-L, White DM. 2009. Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska. Journal of Geophysical research 114, G03002.

These authors examined the isotopic composition and organic matter distribution in soil horizons and particle size fractions from two soils in Alaska, a moist acidic tundra and a moist non-acidic tundra. The organic matter quality and quantity in the deeper part of the active layer and down into the permafrost, material estimated to be between 3000 and 7000 years old indicated high susceptibility to microbial activity, that is, decomposition to CO2 and subsequent release to the atmosphere.

I read this paper as part of my background reading to understand the potential uses of a Picarro field-portable carbon isotope analyser; this paper includes a description of the δ13C values of organic matter throughout the soil / permafrost profiles of these Alaskan soils. These values, and the associated discussion of signatures of microbial activity, suggest it is quite possible to distinguish the source of CO2, permafrost-SOM, deep-SOM, shallow/autotrophic, based on the 13C content of effluxing CO2 and / or CO2 at various depths within a soil profile. Table 5 is particularly valuable in this regard.