Rising CO2 levels likely to have impact on soil, says EU


Source: European Commission, Environment DG

One issue of concern is the relationship between above ground (e.g. by trees) and below ground (e.g. by soil microbes) carbon cycling. Soil fertility appears to play an important role in this process as higher CO2 levels lead to greater competition between microbes and trees for soil nutrients, according to new research.  Soils are an important sink for carbon and understanding how microbes that fix carbon react to changes in soil fertility and atmospheric CO2 may become increasingly important in the context of global climate change.

Researchers from the University of Tuscia, Italy studied soil microbes at the POPFACE1 experimental plantation over a five-year period. POPFACE is a plantation of three species of poplar trees in central Italy with controlled atmosphere facilities. This allowed researchers to test the effects of different atmospheric concentrations of CO2 and levels of soil nitrogen on the ability of microbes to sequester carbon.

The research explored the impact of raised atmospheric CO2 levels on carbon sequestration by soil microbes. When soils were richer in nitrogen, microbes processed more carbon, leading to a greater release of CO2 into the atmosphere. This release of CO2 was also affected by the species of poplar and season. In unfertilised soil where nitrogen was limited, microbes living beneath trees in a raised CO2 atmosphere sequestered more carbon.

The researchers also investigated whether increased CO2 levels would alter the microbial community in the plantation. Nitrogen levels were more important than the CO2 level or the poplar variety in determining the range of microbes in the soil. The research suggests that the application of nitrogen based fertilisers, sometimes used to stimulate growth of young trees, will lead to greater CO2 loss from soils.

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