A "nitrogen bonus" - a speed up in carbon sequestration due to N deposition - has been reported for European forests. The increase of severe drought episodes creates now the opposite concern, i.e. N deposition exacerbating drought effects because of higher water demand arising from N-stimulated leaf area and growth. Since this may negatively affect growth and C sequestration, we term it "N-penalty". This project intends to test the "N-penalty" hypothesis for the Swiss forests. By statistical modeling and quasi-experimental analyses based on N deposition estimates, drought indices and NFI data, we assess interacting effects of N deposition and drought on forest health and productivity.
2020 - 2021