The birds of Pasvik / E. I. Khlebosolov, O. A. Makarova, O. A. Khlebosolova [et al. ; English transl. Nikita Chernetsov]. - Ryazan : Golosgubernii, 2007. - 175 с. : ил., портр.

£./. Khlebosolov The mountain tundra is a landscape for the birds of open habitats. Relatively low mountains situated in Pasvik are characterised by vertical z o n ­ ality from the forest at the bottom to the m ountain tu n d ra on the hilltops. In the lower parts o f the slopes pine or mixed forests grow. T hen a narrow birch forest belt goes (Fig. 2.1.F) which grades into crooked birch forest (Fig. 2.1 .G ). H igher up the mountain tundra with mosses, lichens and low shrub is situated (Fig. 2.1 .H ). Here a large num ber o f wetlands and small lakes may be found. The southern part o f the Pasvik valley is located in the boreal zone and c o n ­ tains pine and mixed pine and birch forests. F u rth er n o rth , boreal zone grades into the alpine zone where birch forests o f the m ountain tu n d ra type prevail (Wikan et al. 1994). In the Pasvik valley the zonal lowland tu n d ra is practically lacking. However, they may be found in some adjacent areas o r even ju t in to Pasvik. Here specific avian communities are formed that are typical o f the zonal tu n d ra and sig­ nificantly differ from avian comm unities o f the m oun tain tund ra. 2 .3 . Main ecological groups of birds The current studies o f comm unity ecology are characterised by gradual tran si­ tion from the description o f the structure o f comm un ities to th e study o f the m e ch ­ anisms o f their formation and functioning. An im po rtan t step in this d irection is identification o f functional relationships between the organism s in the community. To do this it is necessary to identify ecological groups o f different hierarch ical lev­ els related to the degree o f their functional sim ilarity (o r difference) and to u n d e r­ stand the relationships between them . Identification o f the elem en tary ecological