Soil carbon review (backlog No. 1)

This one's from 21 May 2007:
Davidson EA, Janssens IA (2006) Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature, 440:165-173.

A useful article on the face of it, especially in light of Article 3.4 of Kyoto which allows for carbon credits on the basis of increased soil carbon storage. It provides a good summary of many of the concepts and issues relating to carbon cycling in soils...

...but we were frustrated by a few things. Not the least some omissions and errors: for example, activation energies are not, as the authors claim (p. 165), "related to the ambient temperature..." (they create temperature dependence for chemical reactions, but do not themselves depend on temperature - Wiki). The process of carbonate weathering and formation in soils was not considered, a simplification of the idea of "soil" carbon that does not necessarily make much sense given that carbonate dissolution depends on the partial pressure of CO₂. We also felt the list of factors affecting temperature sensitivities of soil organic carbon decomposition (p. 167) was perhaps incomplete. No mention was made, either, of the observations from arid ecosystems that photodecomposition of soil organic matter may be important (see Austin AT, Vivanco L 2006 Nature 442:555-558).

The temperature-sensitivity of soil organic carbon decomposition has been contentious recently, but the authors make no firm conclusion either way, nor makes any great deductive leaps in conclusion. This may be fair enough, given the complexity of the issue. And that's perhaps what the article lacks - sufficient complexity (especially in light of the omissions). It certainly makes for good undergraduate reading, and has well-drawn and informative diagrams that will no doubt find their way into numerous lectures. But cutting-edge review? - maybe not.