Ozone Impacts on Carbon Sequestration in Northern and Central European Forests

The ozone impacts on forest carbon sequestration were assessed for some northern and central European countries. The analysis was based on UN-ECE statistics regarding forested areas, forest growth and harvest rates for the 2000-2005 period. This was combined with ozone exposure — growth response relationships for different forest types and age-classes in combination with nation-wide values for AOT40 April — September.The following conclusions were made: 1. The by far most important countries for carbon sequestration in the forest living biomass carbon stocks were Sweden, Finland, Poland and Germany. 2. The estimated annual increase in the living biomass carbon stocks under current ozone conditions for the ten countries was 171 M t CO2e yr-1, while it was estimated to have been 190 M t CO2e yr-1 under pre-industrial ozone levels. 3. The difference caused by current ozone conditions on the annual living biomass carbon stock change was thus 19 M t CO2e yr-1, i.e. the carbon sequestration in these countries would have been 10 % higher in the absence of the ozone pollution problem. 4. The magnitude of the predicted relative ozone effect for the different countries strongly depended on the gap between forest growth and harvest rates 5. The knowledge regarding ozone impacts on mature trees under field condition is to a large extent incomplete and further research is strongly needed. The abatement of the ozone pollution problem clearly has the co-benefit to increase the carbon sequestration in northern and central European forests for at least some decades into the future.

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