Greenhouse gases from forest soils

Greenhouse gases from forest soils
Reactive nitrogen compounds from agriculture, transport, and industry lead to increased emissions of the greenhouse gas nitrous oxide (N2O) from forests in Europe. Nitrous oxide emission from forest soils is at least twice as high as estimated so far by the Intergovernmental Panel on Climate Change (IPCC). This is one of the key messages of the first study on nitrogen in Europe (European Nitrogen Assessment, ENA) being presented at the International Conference "Nitrogen and Global Change 2011" in Edinburgh, Scotland.

Reactive nitrogen compounds (e.g. NH3 and NOx) are mainly of anthropogenic origin. After their deposition on forests via air, they are partly converted into nitrous oxide (N2O). Following carbon dioxide and methane, nitrous oxide is the third biggest producer of the greenhouse effect. One kilogramme of nitrous oxide is about 300 times as greenhouse-effective as the same amount of carbon dioxide. The ENA study performed by more than 200 scientific and political experts from 21 countries and 89 organisations concludes that the input of reactive nitrogen from air in the European forests so far has been underestimated significantly. Based on the information now available, about 2 to 6% of the atmospheric reactive nitrogen is converted into nitrous oxide that is emitted from forest soil into the atmosphere again. The corresponding estimate of the IPCC so far was about 1% only. Over a forest area of 188 million hectares, deposition of reactive nitrogen increased from 1860 to 2000 by 1.5 million tons per year. This corresponds to an annual increase in reactive nitrogen per hectare forest by about 8 kilogrammes.