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 1D. 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(-1) and is smaller than the annual input by bulk and occult deposition, which combines to approx 1.2-1.5 g N m(-2) yr(-1). 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(-2) yr(-1)), the process of N saturation is apparently slow.