| INTRODUCTION The increase of intensity of open pit extraction of mineral resources results in the increase of the rate of land degradation. This process is common in the northwestern Russia; 22900 ha were damaged in the territory of Leningrad oblast as reported for January 1, 2010. [10]. The processes of ecosystem restoration on disturbed lands were impeded for a diverse reasons. Great amount of overburden rock was placed on the surface in the course of opencast mining; this rock was often very specific by properties, composition, suitability for plant cover restoration, and differed drastically from parent rocks of natural landscapes, to which zonal plant communities were adapted. Low concentrations of nutrients in overburden rock were often the factor, limiting restoration of technogenic ecosystems [38, 42]. Application of mineral fertilizers and organic ameliorants do not often enhance the processes of colonization by vegetation. This was connected with the fact that easily soluble substances were quickly lost by initial soils, and organic fertilizers were intensely mineralized in the absence of developed soil adsorption complex [1, 2]. Quarries of constructional and nonmetallic materials were suitable objects for studying some elementary soil-forming processes. Technogenic and especially post-technogenic ecotopes were good model to study the regularities of colonization by plants the sites without soil and plant cover and to estimate the rates of processes developing at initial stage of ecosystem formation in the course of primary succession. As a rule, the succession of phytocenoses in the territory of rock-disposal complexes occurs gradually, beginning with the appearance of algocenoses. Then, separate plant communities are formed; meadow communities usually dominate at initial stages, and forest communities replace them with time. Regular changes begin in spatially heterogeneous soil layer, as edaphic influence of plants increases. Transformation of biogenic (soil) layer occurs along with the phytocenosis change; first, the sod of young soils is destructed in the course of displacement of meadow vegetation by the forest one, and a thin eluvial horizon can be formed under phytogenic fields of coniferous species. It was noted that microbial cenoses in young ecosystems had no pronounced dominants, and this was typical for early stages of ecosystem development unlike the stable ecosystems [10]. Some researchers considered that planting of seedlings was an optimal method of reclamation, because soil development was closely connected with the plant cover formation and accumulation of critical mass of dead organic matter. One can enhance the rate of pedogenetic processes by promoting the appearance of closed tree stand [6]. Plant community, which determines the appearance and development of all other components of ecosystem via starting the biological turnover of the matter and the main soil- forming processes [6]. |
