Transformation and Reconstitution of Vegetation in the Pre-Baikal

The work represents the results of perennial studies of the structural-dynamic organization of the phytocoenoses, which are subjected during a long period to anthropogenic impact in different, for geographical conditions, areas of western and south-eastern Pre-Baikal. The composition of phytocoenoses, which form at cuttings of forests of different composition and typology is found out. The following parameters are determined: species composition, synfolial differentiation and dominant species of the soil cover reflecting the dynamics of reconstitutional stages of polydominant light-coniferous forests of Pre-Baikalian type. We noticed the peculiarities of transformation and reconstitution of the coenoses, which during a long period are used for haying and pasturage formed on the site of earlier cut timber stands at the boundary with the extrazonal steppe. During last decades, a gradual forestation of these territories is observed, the steppe plants species in the soil cover are replaced by forest species characteristic for the light-coniferous taiga. On the site of cuttings of dark-coniferous taiga in the first half of the last century in the southern part of Pre-Baikal, forests form with dominance of more hydrophilic trees species in undergrowth and young growth – fir and spruce replace cedar everywhere. This is probably due to secular forests dynamics with replacement of forest forming trees species on the background of climate changes during last decades. There are as well changes in the species composition of plants on the soil cover of forming dark-coniferous taiga.