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Soils Reveal Global Warming Paradox

Story supplied by LU Press Office

Forests may not be able to slow down global warming as effectively as previously thought according to new research published in Science by a team from the Lancaster Environment Centre and the University of York.

The research found that as CO2 levels rise, the potential of forest soils to absorb atmospheric CO2 - and thereby slow down global warming - may be much less than previously thought.

The Natural Environment Research Council funded experiment was carried out on young trees in Lancaster University's prominent "Field of Solardomes" that used to overlook the M6 motorway.

The study warns that the potential of terrestrial ecosystems to absorb the increasing amounts of CO2 that we add to the atmosphere every year- and thereby slow down global warming - may be considerably smaller in a future "high CO2 world" than previously thought.

The researchers planted over 500 young trees of six species in eight tonnes of specially treated soil in twelve of the solardomes, and measured the amount of carbon that the trees were removing from the atmosphere and transferring to the soil over two years. The domes were filled with air at one of four different CO2 levels. One group was at current CO2 levels (around 380 parts per million) and the other three groups were at around 480, 580 and 680 parts per million. These are the CO2 concentrations expected to be reached at different points within the next 100 years.

Although a significant quantity of new carbon was retained in the soil beneath all trees, scientists discovered that with increasing CO2 concentration less new carbon was retained in the soil - the converse of what was expected. It was assumed that under higher CO2 conditions the trees would grow faster and release more carbon into the soil via the roots and that therefore, more carbon would be retained in the soil. The experiment showed that this may not be the case, because at increased CO2 concentrations more of the extra carbon transferred to the soil by the tree roots was simply released back into the atmosphere through the respiration of soil micro-organisms.

Fri 16 September 2005