Successions which take place while draining mires and paludified forests are of postreclamation nature, and affect cenotic and species diversity of the forests. K.K.Bush and A.A.Abolin (1968) distinguished three stages in the drainage succession: initial stage of slow changes in the communities, fundamental transformation stage, and relative stabilization stage. The initial stage in the succession is 15-30 years long.

Investigations were carried out in the most wide spread sedge- and dwarf shrub-sphagnum types of pine stands drained 20 years ago. The woody layer of the communities changed considerably through this period. Under mesoeutrophic conditions pine density tended to decrease and the share of birch to grow, a great number of spruce saplings appeared under the canopy. Under oligotrophic conditions birch takes root in the undergrowth. Species diversity of woody vegetation grows.

Soil cover is quick to react to changes in environmental conditions. A general trend is observed towards the diminution in the role played in the soil cover by hygrophilous mire species and the growing abundance of mesophilous species. As the stand density in the sedge-sphagnum pine stand increases the total cover of the grass-dwarf shrub and moss layers gets more sparse the species diversity however getting richer.

Investigations carried out by L.S.Kozlovskaya (1976) demonstrated that already in the first postdrainage years the abundance and the number of groups of animals who mineralise plant residues grew, the active life of invertebrates grew longer, a new more xerophilous cenosis was formed.

The data obtained allow to conclude that forest drainage results in the fundamental transformation and increases cenotic and species diversity in paludified forest ecosystems in the first postdrainage period.