How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Soil Organic Carbon in Old-Growth Forests
Zhou, G., Liu, S., Li, Z., Zhang, D., Tang, X., Zhou, C., Yan, J. and Mo, J. 2006. Old-growth forests can accumulate carbon in soils. Science 314: 1417.

The authors note that "old-growth forests have traditionally been considered negligible as carbon sinks because carbon uptake has been thought to be balanced by respiration." As a result, they report that "the soil carbon balance of old-growth forests has received little attention."

What was done
In an attempt to rectify this situation, Zhou et al. say they "conducted a study to measure the long-term dynamics (1979 to 2003) of soil organic carbon stock in old-growth forests (age > 400 years) at the Dinghushan Biosphere Reserve in Guangdong Province, China."

What was learned
The eight scientists report that "soil organic carbon concentration in the top 20-cm soil layer increased between 1979 and 2003 from about 1.4% to 2.35% at an average rate of 0.035% each year," also noting that "measurements on a total of 230 composite soil samples collected between 1979 and 2003 suggested that soil organic carbon stock in the top 20-cm soil layer increased significantly during that time (P < 0.0001), with an average rate of 0.61 Mg C ha-1 year-1."

What it means
In discussing their results, Zhou et al. state that although "the driving forces for this observed high rate of soil organic carbon increase in the old-growth forests are not clear at present," their study "suggests that the carbon cycle processes in the belowground system of these forests are changing in response to the changing environment [our italics]."

We agree, having reported frequently on analogous observations in the aboveground portions in such forests (see, for example, many of the items we have archived under the heading of Forest (Old) in our Subject Index, where the researchers involved in the work reported there have often suggested that the ongoing rise in the air's CO2 content is likely a - or even the - primary force behind the phenomenon, aided by warming and in some cases enhanced nitrogen deposition).

Reviewed 28 February 2007