by Andrei IVANOV, Cand. Sc. (Geogr.), Lomonosov Moscow State University Now who bears the palm in landscape modification-of all the beings populating the globe Man is considered to be in the lead, sure. But do we know that animals, too, are contributing to environmental modification by changing their habitats and creating specific geosystems of different hierarchical levels? Now and then they evolve into a principal formative factor of the environment. THESE BUSY DIGGERS Zoogenic complexes created by burrowers are fairly common here and there. In tundra plains of the north these are colonies of lemmings and Arctic (polar) foxes; these are badgers in the forest belt zone; and gophers and marmots in steppes (vast grassy plains of southeastern Europe and central Siberia) and semideserts. Lemmings dig an intricate system of far-flung burrows with rather long passages (15 to 35 cm, or 6-14 in.), nest and feed homes, and 5 to 20 inlet holes. Their colonies give rise to specific plant communities and lumpy microrelief features that may be many inches tall. The vital activity of these rodents is responsible for the higher presence of humus (organic matter) inстр. 38 soil, good humidity and aeration of surface soil and more vigorous processes within it. The depth of the active soil layer increases, too. The biogenic elements obtained from their excretions are mineralized fast to join in the circulation of substances, while the holes and "tunnels" dug by the rodents improve soil drainage and aeration, and cause to increase thaw depths from 35 cm (14 in.) to as much as 60-70 cm (24-28 in., respectively). A colony of such tireless diggers is able to move as much as 250 kg of earth per hectare (or 100 kg per acre). Depending on how long a colony of lemmings has been inhabiting a particular patch of ground, it gives birth to a specific plant community (phytocenosis), with many plants exhibiting profuse growth compared with their neighbors. Thus, if we take the Vrangel Island loca ... Read more