Assessing ozone and nitrogen impact on net primary productivity with a Generalised non-Linear Model

Some studies suggest that in Europe the majority of forest growth increment can be accounted for N deposition and very little by elevated CO2. High ozone (O-3) concentrations cause reductions in carbon fixation in native plants by offsetting the effects of elevated CO2 or N deposition. The cause-effect relationships between primary productivity (NPP) of Quercus cerris, Q. ilex and Fagus sylvatica plant species and climate and pollutants (O-3 and N deposition) in Italy have been investigated by application of Generalised Linear/non-Linear regression model (GLZ model). The GLZ model highlighted: i) cumulative O-3 concentration-based indicator (AOT40F) did not significantly affect NPP; ii) a differential action of oxidised and reduced nitrogen depositions to NPP was linked to the geographical location: iii) the species-specific variation of NPP caused by combination of pollutants and climatic variables could be a potentially important drive-factor for the plant species' shift as response to the future climate change. (C) 2012 Elsevier Ltd. All rights reserved.