Effects of nitrogen deposition on nitrogen cycling in an Aleppo pine stand in Athens, Greece

High levels of nitrogen deposition measured in throughfall fluxes in 2002, reaching 38 kg ha(-1) year(-1), affected the biogeochemical cycle of N in an Aleppo pine (Pinus halepensis) stand situated in Athens, the capital of Greece. The N fluxes in bulk deposition were far lower than those in throughfall indicating high levels of dry deposition in the city of Athens. The amounts of N in litterfall and those stored in the forest floor and mineral soil were not high, while the mean residence time of N in the forest floor, derived from fluxes equations, decreased considerably due to the high levels of N fluxes in throughfall deposition. Nitrogen concentration in needle tissues was high and this resulted in a high ratio of N/Zn. Zinc availability was low due to the alkaline nature of soil in the study area. Fast N cycling may affect the living status of Aleppo pine, which is an oligotrophic plant species capable of occupying poor soil sites. Nitrogen eutrophication may adversely affect forests grown on calcareous soils by developing nutrition imbalances between N and micronutrients, the solubility of which depends on soil pH values.