Global Change Biol. 14, 2910–2922 (2008)
The influence of elevated atmospheric CO2 on soil's ability to store carbon is a matter of great debate, with some studies reporting increases in soil organic matter — and hence carbon storage — and others, no change or even a loss. Now, a nine-year investigation suggests that increased litterfall could enhance soil carbon storage in a greenhouse world.
John Lichter, of Bowdoin College, Maine, and colleagues, examined the effect of CO2 enrichment on soil carbon sequestration in a loblolly pine plantation. The forest, one of many Free Air CO2 Enrichment (FACE) experiments across the globe, was exposed to elevated CO2 concentrations (200 microlitres per litre above ambient levels) between 1996 and 2005. During this time, the forest floor accumulated an extra 30 grams of carbon per square metre per year. This build up of soil carbon could not be attributed to a decrease in the decomposition of organic matter and was probably the result of increased litterfall.
Although this represents a noteworthy increase in forest carbon storage, it is still small relative to human emissions, say the authors. However, with the first generation of FACE facilities set to close, the sustainability of this carbon sink will remain a mystery for a long time to come.