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

In the alpine regions, more than half of the yearʹs 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% of N released by N 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.