Epiphytic lichens indicate recent increase in air pollution in the Mongolian capital Ulan Bator

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Mongolia is one of the least densely populated countries of the world with 2·6 million people occupying an area of 1·5 million km². A high proportion of the population and economy is concentrated in the capital Ulan Bator, which has 1 million inhabitants. Ulan Bator is characterized by its high elevation (1350 m), low precipitation (300 mm), high annual sunshine duration, and its location in a basin. The city is surrounded by mountain ranges to the north and to the south. Furthermore, it is the coldest capital of the world with an annual mean temperature of −3·7°C (Hilbig et al. 2004). Outside Ulan Bator and a few industrial areas, including a large copper plant near the second-largest city Erdenet, Mongolia’s air is extremely pure (ADB 2006). Therefore, Mongolia’s forests, which cover 10% of the country (Erdenechuluun 2006) harbour a rich epiphytic lichen vegetation (Cogt 1995). Most of these woodlands are conifer stands that form the southernmost range of the continuous Siberian taiga forests (Gunin et al. 1999). Eighty percent of the forest area of Mongolia is covered by Larix sibirica (Savin et al. 1978), while other important tree species in the taiga include Pinus sibirica, P. sylvestris, Picea obovata, Abies sibirica, and Betula platyphylla (Hilbig 1995; Dulamsuren et al. 2005). Dominant epiphytic lichen species in the larch-dominated taiga include Bryoria fuscescens, B. nadvornikiana, Evernia mesomorpha, Flavopunctelia soredica, Hypogymnia bitteri, H. physodes, Lecanora symmicta, Melanohalea septentrionalis, Parmelia sulcata, Usnea sp., and Vulpicida pinastri (Biazrov 1974; Hauck et al. 2007).