Leśne Prace Badawcze / Forest Research Papers December 2015, Vol. 76 (4): 401–409 DOI: 10.1515/frp-2015-0039 Available online: www.lesne-prace-badawcze.pl reView article Submitted: 20.01.2015, reviewed: 01.02.2015, accepted after revision: 19.05.2015. © 2015 M. Baciak et al. e-ISSN 2082-8926 The effect of selected gaseous air pollutants on woody plants Michał Baciak, Kazimierz Warmiński, Agnieszka Bęś* University of Warmia and Mazury in Olsztyn, Department of Environmental Toxicology, ul. Prawocheńskiego 17, 10-720 Olsztyn, Poland * Tel. + 48 89 5233336, e-mail: agnieszka.bes@uwm.edu.pl Abstract. the article discusses gaseous air pollutants that have the greatest impact on forest ecosystems. this group of pollutants ncludes sulfur dioxide (SO 2 ), nitric oxides (NO and NO 2 ) and ozone (O 3 ). in the 20 th century, the major contributor to forest degradation was sulfur dioxide, a gaseous substance with direct and po- werful phytotoxic and acidifying effects. Since then, sulfur dioxide emissions have been signifcantly reduced in Europe and North america, but they continue to grow in east asia along with china’s economic boom. Nitric oxides affect woody plants directly by entering through the stomata and indirectly through soil acidifcation and environmental eutrophication. Ozone, in turn, is found in photochemical smog and is produced by conversion of its precursors (nitric oxides, organic compounds and carbon monoxide). it is a strong oxidizing agent which disrupts various physiological processes, mostly photosynthesis and water use in plants, but is also the air pollutant that exerts the most toxic effect on forest ecosystems. Keywords: forest degradation, air pollution, ozone, sulfur dioxide, nitric oxides 1. Introduction Forest ecosystems, which cover about one-third of the world’s land area (Matyssek et al. 2012), present one of the main parts of biosphere. they affect the composition and the quality of atmosphere and also shape climate conditions both on regional (local) and global scales. the presence of forest ecosystems, which serve as the connection between atmo- sphere and biosphere, infuences cycling of large amounts of matter as well as energy fow in nature (Noe et al. 2011). Forests could be found in almost all climate zones. they are very diverse both in their species composition and in their vertical and horizontal structure (Misson et al. 2007). Owing to the large area covered by forests, they are very sensitive to pollutants present in atmosphere, especially gases (inclu- ding sulphur dioxide (SO 2 ), nitric oxides (NO x ) and tropos- pheric ozone (O 3 )). Such pollutants affect forest ecosystems disrupting growth of trees (wamelink et al. 2009; liu et al. 2011), changing species composition or increasing suscep- tibility of forests to biotic factors such as insect outbreaks (Paoletti et al. 2010). acid gases (SO 2 and NO x ) indirectly affect forests by acidifying soils, which changes soil fuids and infuences accessibility of nutrients (Bytnerowicz et al. 2007; wu et al. 2011). currently, around the world, more and more attention is paid to air quality parameters. the re- search is being conducted in order to limit negative effects of gaseous air pollutants on forest ecosystems. Cross-bor- der movement of air pollutants to large distances presents another signifcant problem. Owing to such reasons, Japa- nese forests are infuenced by pollutants originating from Eastern Asia (Gbondo-Tugbawa, Driscoll 2002; Chiwa 2010). in europe during 1970s and 1980s, increased emis- sion of sulphur dioxide, nitric oxides and dust resulted in ca- tastrophic destruction of forests in central and northern parts of the continent together with the so-called ‘black triangle’ covering the bordering areas of Poland, czechoslovakia and GDr. large number of environmental projects were imple- mented in order to improve air quality in that region as a re- sult of which the situation in the area signifcantly improved. New forest areas emerged as a consequence of decreased emissions of toxic air polluting compounds (Blažková 1996; Szaro et al. 2002; Bytnerowicz et al. 2004; Maňkovská et