Simulation of soil hydrology and establishment of a nitrogen budget of a Mountain Forest

The water fluxes through the mountainous forest ecosystem ‘Mühleggerköpfl’ were simulated by means of the mechanistic soil physical model Hydrus ID. The objective was to set up a nitrogen budget in order to decide if the ecosystem accumulates nitrogen or if nitrogen leaks from the site. The simulated annual loss of N by percolation ranges between 0.4 and 1 g N m^?2 yr^? and is smaller than the annual input by bulk and occult deposition, which combines to approx 1.2–1.5 g N m^? yr^?. Obviously the forest soil presently accumulates N. With an N input-rate exceeding the N output, the operationally defined status of N saturation is not yet reached. Comparing the magnitude of the N pool in the soil (several kg N m^?2) with the rate of the annual increase (a few g N m^?2yr^?1), the process of N saturation is apparently slow.