Fig. 2.

Flows of N between the plants and soil under elevated CO₂ and O₃. Even though elevated CO₂ increases plant biomass production and thus increases the plant demands of N, the mineral N released in the decomposition process is quickly taken up by the plants. In contrast, elevated O₃ decreases plant biomass production and thus the demand of N by the plant. Since the input of organic material is reduced under elevated O₃, the mineralization process is also decreased, which leads to an accumulation of total N. Lastly, possibly due to the availability of organic material under elevated O₃, a higher abundance of the denitrifier gene was observed compared to ambient O₃ plots.