Nitrogen oxides emissions in relation to microbial parameters at 13 European forest sites

Kaltenburg-Lindau

2004

S. 5151

SonderdruckBandaufführung

120773

Nitrous oxide is one of the main greenhouse gases produced by microbes in soils. Together with NO it is a precursor of ozone. European forest soils are substantial sources of nitrogen oxides and may become even more in future. Wihtin the EU-Project NOFRETETE the underlying microbial processes were studied. Thirteen soils from different European countries were investigated for microbial biomass, nitrogen mineralisation, nitrification, substrate availablity and microbial community composition. The results of these analyses were related to field measurements on nitrogen deposition and the emission of nitrogen oxides. In addition the effects of temperature and soil moisture on gas exchange were studied in incubation experiments. The analyses of potential nitrogen mineralisation and microbial biomass N showed that there were clear differences of microbial turnover and nitrogen retention between the sampling sites, which were mainly related to soil moisture and pH value. NO production increased exponentially with soil temperature. Very high activation energies of 125 to 199 J K-1 mol-l were observed in soils from two beech forests in Central Europe. N2O emissions also increased exponentially with soil temperature but activation energies were lower. Increasing soil moisture lead to enhanced N2O emissions in moist soils, whereas NO production declined when optimum moisture conditions were exceeded. From our results we concluded that nitrogen deposition aswell as temperature are important factos triggering nitrogen oxides emissions from forest soils. However, different microbial communities show different sensitivities to these influences.