The experimental research in Salatín (Western Tatra Mts., Slovakia) address the impact of nitrogen (N) deposition on ecosystem of alpine grasslands. The site was exposed during last 50 years to high acid deposition with maximum rates of wet deposition at least 15–20 kg N ha-1 yr-1 and 20–25 kg S ha-1 yr-1. The experiment consists of 5 replicated treatments: 20, 60, and 150 Kg N ha-1 yr-1, 50 Kg P ha-1 yr-1 and the control, 25 plots in total.
The achieved results indicate significant effects of N deposition on the grassland ecosystem chemistry and productivity in very acid conditions of the site (pH 3.5 in the control treatment). The experimentally increased N deposition resulted in a depletion of both base cations and soluble aluminum, and an increase in extractable iron concentrations. As a consequence, the aboveground biomass decreased. We suggest that this site have reached a new and potentially more toxic level of soil acidification in which aluminum release is superseded by iron release into soil water (Bowman et al., 2008).
The study demonstrates that the alpine meadow ecosystem at Salatín Mt. is fully saturated with N, which restrict microbial activities. The application of phosphorus (together with potassium) stimulate the utilization of nitrogen, enhance the primary production, thereby saturate the microbes with C-substances and probably protect the ecosystem against acidification.
We did not record decrease of plant species richness (usual consequence of N enrichment) probably because of previous selection of tolerant species by long-term high rates of N deposition of N. However, decreased abundance of lichen species Cetratia islandica and increased abundance of grass species Festuca supina were recorded recently. Certain shifts in abundance of some other species were detected as well.

This research was supported by NSF grant No. OISE-0112281 and VEGA grant 02/0217/09.