Inorganic nitrogen storage in alpine snow pack in the Central Alps (Switzerland)

In the alpine regions, more than half of the year`s precipitation is conserved as snow. We investigated inorganic ion storage in snow pack at 2500 m (a.s.l.) in the Central Alps, Switzerland. Chemical composition of snow was dominated by nitrogenous and sulphate ions. Ion pools showed high local and inter-annual variability (2002, 2003), but differences in ion pools were not simply due to varying snow depth. The highest soluble nitrogen (N) pools were found in March (1.1-1.7 kg N ha(-1)). Later, in spring (April and May), N pools in snow were significantly lower (0.5-0.8 kg N ha(-1)). Ion storage in snow was compared with N fluxes in rain, which ranged between 2. 0 kg and 3.3 kg N ha(-1) summer(-1). Both forms of wet precipitation yielded a total wet N input into alpine grasslands of maximal 5.0 kg N ha(-1) a(-1). Atmospheric N deposition data for alpine ecosystems in the European Alps are rare and the monitored data here deviate by a factor of 2 from modelled N deposition. Nitrogen deposition in the alpine zone of the Central Alps is much smaller than previously assumed, but N pools stored in snow correspond to, at the most, 34 mineralisation in alpine soils. Net N mineralisation accounts for only a fraction of the annual N uptake of alpine plant; thus, the additional N source by melting snow contributes substantially to alpine plants N uptake, particularly during periods when N demands are highest.