Many plant species in the arctic ecosystems are placed at the boundaries of their areals and have patched distribution. Even the slight anthropogenic impact on the plant species population may result in the deformation of population structure, that was stated after the millennium of evolutional process, and to the modification of populational-genetic and phytocoenotic parameters of ecosystem. The most probable consequences of these changes is the loss of ecosystem biodiversity, that demonstrates in the loss of species number in the phytocoenosis, changes natural species with the apophyte and adventive plant species.
The comparative evaluation of tolerance of the tundra phytocoenosis and primitive plant aggregations to the different anthropogenic impacts and their possibilities to autorevegetation was investigated in 1991-1995 years at the Yamal peninsula and Bolshezemelskaya tundra (northern hypoarctic tundra subzone). The zonal plant communities in these conditions are the dwarf shrub and willow shrub tundras, that located at the plain habitats and have small typological diversity.
The more vulnerable communities are the patched dwarf shrub tundras and primitive plant aggregations of deflational patches, that are located at high parts of hills and covered by the thin snow layer in winter. The stability and revegetation of plant cover (PC) in these conditions are very difficult, such as the soils usually have the primitive development, poor nutrient compounds and good drainage. The activization of wind erosion processes and the increase of scale opened patches take place after the disturbances of PC. The most difficult revegetation takes place after the efflorescence of the melkozem layer. The similar sites at the Yamal peninsula and Bolshezemalskaya tundra have squares at hundreds of hectares. The revegetation of plant projective cover at the boring well sites, that are located at these places has 10-20% in 2 years after works were terminated. The pioneer species that first occupy these sites are /Salix nummularia, Arctous alpina, Empetrum hermaphrodium, Leymus arenarius, Festuca ovina, F. rubra, Tanacetum bipinnatum, lichens of Stereocaulon genus and some other plant species. The first and middle stages of revegetation are characterized by the presence of the adventive plant species.
Herbaceous and herbaceous-moss bogs are placed at other pole of tolerance. These bogs are located at the relief depressions and come across the rivers valleys and between them. These plant communities are characterized by the fast revegetation of PC and the slight introgression of apophyte and adventive species in consequence of peculiar conditions. But after the intensive and large-scale deformation of these bogs with the use of heavy tractors, after the full PC deletion and homogenization of soil layers possible the considerable demonstration of termokarst phenomenon and forming different lake systems. The recovering of these ecosystems is very problematic.
The good indicators of the PC changing in tundra after anthropogenic impacts are the slope and flood meadows. These communities are located at the ecological niches with the optimal microclimatic and edaphic conditions, and have the most rich plant species diversity. After invasing in the region of anthropophyte plant species these meadows are most favorable and basic polygons for their primary adaptation and selection of varieties, that have possibilities for the introgression into zonal plant coenosiums.
Dr. Igor Lavrinenko Institute of Biology Komi Sci. Centre Ural Division, RAS Kommunisticheskaya, 28 167610 Syktyvkar, RUSSIA Phone: 7 (8212) 42 53 04 Fax: 7 (8212) 42 01 63