Soils: carbon sink or source?

Article for 26 March 2007: 

Meir P, Cox P, Grace J. 2006.The influence of terrestrial ecosystems on climate. Trends in Ecology and Evolution 21:254-260.

This is a review article that promised a stimulating discussion of the global function of soils and their response to one of the most significant (or at least newsworthy) issue of the 21^st century - Climate Change.

The past few decades have seen considerable effort from the scientific community into understanding the interactions between global carbon cycles and global climate. Much of this effort has gone into understanding the ocean-atmosphere systems (perhaps understandably, given the proportion of Earth's surface occupied by oceans) with the uncertainties about oceanic responses to projected increases in atmospheric CO₂ now estimated to be lower than for other Earth sub-systems.

The authors review short- to medium-term mechanisms by which terrestrial ecosystems influence global climate. There is no discussion for climatic effects over "geological" time scales, such as biotic-atmosphere-silicate weathering effects and feedbacks, or the influence of the clay mineral factory in soils on organic carbon stabilisation. It's a frustrating review though, identifying many areas where we have insufficient knowledge of the influence of terrestrial carbon cycling on climate, but not really pointing the way forward except to identify, in general terms, the type of information needed.

We wondered whether the scope of the problem is just too large, requiring a "theory of everything" to generate any definitive answers. Nevertheless, it's a useful review, and is well-suited as reading material for our first-year unit in Earth Systems as an introduction (or revision material) to short- to medium-term carbon cycling.  

Photograph by blog author