Modelling of nitrogen dynamics in an Austrian alpine forest ecosystem on calcareous soils : A scenario-based risk assessment under changing environmental conditions

Wien

2007

S. 159-165

SonderdruckMonographie

137648

We modeied the behavior of an Austrian alpine forest ecosystem on calcareous soils underVhanging ciima'te and atmosp'heric nitrogen deposItion scenarios. The change ofnitrate leaching, emission rates of nitrogen Compounds, and forest productivity were caiculated using four process-oriented modeis for the periods 1998-2002 and 2048-2052. Each model reflects with high detail a segment of the ecosystem: PnET-N-DNDC (photosynthesis-evapotranspiration-nitriflcation-denitrification-decomposition; shortterm nitrogen cycling), BROOK90 (water balance for small and homogenous forest watersheds), HYDRUS (water flux in complex and heterogenous soils), and PICUS vi .3 (forest productivity). The nitrogen balance model (NBM) combines the individual results into a comprehensive picture and extends the specific values beyond the limits of the individual modeis. The evaluation of the findings was outlined with TRAGE, a model enabling a long-term prognosis of nitrogen cycling in annual time steps. Temperature increase and nitrogen input are influenced by various components and processes of the forest ecosystem. An increase of the temperature of 2.5°C led to an enhancement of the N2O emission rates and affected the mineralization and the nitrification rates with the consequence of increased nitrate leaching into the subsoil. Enhanced nitrogen input also showed notable effects on nitrate leaching.