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Carbon Contents of Nordic Forest Soils
Callesen, I., Liski, J., Raulund-Rasmussen, K., Olsson, M.T., Tau-Strand, L., Vesterdal, L. and Westman, C.J.  2003.  Soil carbon stores in Nordic well-drained forest soils - relationships with climate and texture class.  Global Change Biology 9: 358-370.

Bellamy et al. (2005) recently determined that significant stocks of carbon had been lost from the top 15 cm of soils across England and Wales between 1978 and 2003, which phenomenon they attributed to "climate change," noting that over the period of study the mean temperature of England and Wales had risen by approximately 0.5C; and because of their stating that "losses of soil carbon in the UK, and by inference in other temperate regions, are likely to have been offsetting absorption by terrestrial sinks," their work was reported prominently in the popular press, where one account said that "rising temperatures resulting from climate change are likely causing soil in England and Wales to lose large amounts of carbon, possibly further contributing to the greenhouse effect."

It was a tidy little feedback loop of the type adored by climate alarmists: it was positive, and, therefore, self-enhancing.  However, as is revealed by the study of Callesen et al., its applicability is much less wide-ranging than it has been made out to be.

What was done
Soil organic carbon (SOC) contents of forest floors and mineral soils to a depth of 100 cm were determined for 234 well-drained Danish, Finnish, Norwegian and Swedish forests between latitudes 55 and 68N and longitudes 6 and 28E, after which a number of analyses were performed on the data.

What was learned
Callesen et al. report that "soil organic carbon in forest floors and mineral soil + forest floors was positively correlated with temperature and precipitation in the study region."  In addition, they say that "a similar increase in SOC with temperature and precipitation was found in nine pine stands on sandy soils within the same latitude range but between 22 and 29E (Vucetich et al., 2000) representing the same temperature gradient but a lower precipitation range."  The positive correlation with temperature was greatest for coarse-textured soils, less for medium-textured soils, and negligible for fine-textured soils.

What it means
The Nordic scientists say "the increase in SOC with temperature and precipitation is interpreted as an indirect effect of higher net primary production."  More specifically, they say that, in Europe, "increasing site productivity has been reported in both nemoral forests and in boreal forests at higher latitudes (Eriksson and Karlsson, 1996; Skovsgaard and Henriksen, 1996; Cannell et al., 1998)," and that this increase "could be attributed to increased atmospheric CO2 concentrations along with the fertilizer effect of nitrogen deposition, and management regimes optimizing forest production."

In light of these broad-based findings, it can be appreciated that just the opposite of what Bellamy et al. claim to be occurring in the top 15 cm of soils in England and Wales is happening in the top 100 cm of soils throughout much of the rest of Europe, producing a negative feedback to both rising air temperatures and CO2 concentrations.

Bellamy, P.H., Loveland, P.J., Bradley, R.I., Lark, R.M. and Kirk, G.J.D.  2005.  Carbon losses from all soils across England and Wales 1978-2003.  Nature 437: 245-248.

Cannell, M.G.R., Thornley, J.H.M., Mobbs, D.C. and Friend, A.D.  1998.  UK conifer forests may be growing faster in response to increased N deposition, atmospheric CO2 and temperature.  Forestry 71: 277-296.

Eriksson, H. and Karlsson, K.  1996.  Long-term changes in site index in growth and yield experiments with Norway Spruce (Picea abies L.) (Karst) and Scots Pine (Pinus sylvestris) in Sweden.  European Forest Institute Research Report 5: 79-87.

Skovsgaard, J.P. and Henriksen, H.A.  1996.  Increasing site productivity during consecutive generations of naturally regenerated and planted beech (Fagus sylvatica L.) in Denmark.  European Forest Institute Research Report 5: 91-97.

Vucetich, J.A., Reed, D.D., Breymeyer, A., Degorski, M., Mroz, G.D., Solon, J., Roo-Zielinska, E. and Noble, R.  2000.  Carbon pools and ecosystem properties along a latitudinal gradient in northern Scots pine (Pinus sylvestris) forest.  Forest Ecology and Management 136: 135-145.

Reviewed 28 September 2005