93 Beskydy, 2010, 3 (1): 93–102 © Mendelova univerzita v Brně ISSN: 1803-2451 Air pollution load and nutrient status of Norway spruce forest stands in the north-western part of Slovakia Z. Sitková, P. Pavlenda, H. Pavlendová, T. Priwitzer, T. Hlásny Z. Sitková, P. Pavlenda, H. Pavlendová, T. Priwitzer, T. Hlásny, National Forest Centre – Forest Research Institute in Zvolen, T. G. Masaryka 22, 960 92 Zvolen, Slovakia, sitkova@nlcsk.org Abstract: Sitková, Z., Pavlenda, P., Pavlendová, H., Priwitzer, T., Hlásny, T. 2010: Air pollution load and nutrient status of Norway spruce forest stands in the north-western part of Slovakia. – Beskydy, 3 (1): 93–102 The article summarizes the results of research of air pollution load, site conditions, and nutrition of spruce stands in the Kysuce and Orava regions (Beskydy Mts.). The region was intensively exposed to air pollution from emission sources in neigh- bouring countries mainly in the 1970s and 1980s. At present, this region is affected by a vast decline of spruce stands, which is thought, at least partly, to be related to air pollution. Long-term research during the last decade indicated: i/ decrease in SO 2 and NO x concentrations, ii/ although the trend of sulphate concentration in precipi- tation is decreasing, the deposition of sulphur and especially nitrogen remain rela- tively high, iii/ in general, there is no evidence of continued forest soil acidification, and the share of the area with an exceedance of critical load of total acidity is decreas- ing, iv/ the nutrition status of spruce is relatively good, v/ ground-level ozone exceeds the concentration that could damage the trees. Key words: air pollution, atmospheric deposition, forest soils, trees nutrition, spruce stands Introduction Acid emissions (especially SO 2 and NO x ) to the atmosphere culminated at the break of the 80s and 90s throughout Central Europe. However, intensive research of air pollution im- pacts on forest started only aer emissions had declined or stablised. The currently observed worsening of forest health status or even exten- sive forest decline indicates that some roots of this problem lie in the former anthropogenic load. This area did not receive too much atten- tion in the past on a national scale, therefore questions that have arisen in relation to recent spruce decline lack many univocal answers (Minďáš, Pavlenda, 2004). North-western Slova- kia is one of the regions with the most intensive air pollution impact on forest soils (Pavlenda, Ištoňa 2003; Pavlenda, Ištoňa, 2004; Pichler et al., 2006). Therefore, attention was paid to a de- tailed investigation of current air pollution sta- tus, nutrition of spruce stands, and persisting anthropogenic load. Such knowledge allows for the stating of starting points for forest manage- ment, and the identification of potential risk to forests in this region. This paper summarizes recent knowledge regarding the following indicators of air pollu- tion load and the impact thereof on forest eco- systems: air pollution, critical loads exceedance, chemical composition of precipitation (deposi- tion), litterfall, soil solution, soil conditions, and forest stands nutrition. Material and methods Results of several research projects analysing the data from various research plots or regions as well as from various time periods (Fig. 1) are summarized in this paper. Methods used for the analysis of respective indicators of air pollu- tion load are given in Tab. 1. The study region is part of the forest regions Západné and Stredné Beskydy; and the geomor- phological units Moravsko-sliezske Beskydy, Turzovská vrchovina, Jablunkovské medzi- horie, Kysucké Beskydy, Kysucká vrchovina,