What was done
At a site on Great Dun Fell in the United Kingdom, root birth and death rates were determined from biweekly mini-rhizotron video images obtained over one experiment of 6 month's duration and another of 18 month's duration in an upland grassland where the soils of half of the treatment replications were artificially maintained 2.8°C above ambient at a depth of 2 cm.

What was learned
Heating the soil of the ecosystem by 2.8°C above ambient increased both root production and root death by approximately equivalent amounts.

What it means
In the words of the authors, "the data presented here suggest that the effect of a warmer climate will be a similar acceleration in both [root] birth and death processes and these will have no direct effect on the soil carbon store."  Hence, we further conclude that this null effect of temperature suggests that a concurrent increase in the air's CO2 concentration likely would lead to an increase in the soil carbon store, because of the increase in plant productivity that would be provided by the aerial fertilization effect of atmospheric CO2 enrichment.  And this CO2-induced increase in soil carbon storage would tend to slow the rate of rise of the air's CO2 content.