Influence of Fires on Pine Forest Floristic Diversity of the Eastern Transbaikal Territory

The article shows the effect of extensive and repeated forest fires on the floristic diversity of pine forests typical for the forest-steppe zone of the Eastern Transbaikal territory. Pine forest general description carried out according to the materials of the forest valuation of1994, before the extensive fires. The floristic composition of long-term non-burning plant communities in different stages of secondary succession after fires was determined by the method of sample plots. Indexes of species abundance accumulation and rare species, and the share of forest and adventive plant species were used to estimate the biodiversity of plant communities. Pine forestland is formed by a variety of forest types, where rhododendron pine forests dominate by area; while cereal mixed herbs pine forests occupy the smaller area. Sedgy, mountain-lapideous, ledum and riverine pine forests occupy up to 5 % of the total area. Area ratio of monodominant and oligodominant forests to a certain extent associated with slope direction. Monodominant forests areas are larger than oligodominant forests areas on the slopes of the North-West and the South-West exposure; while oligodominant forests occupy large areas on southern, northern, western and eastern slopes. Young and middle-growth plantations were more than 50 % of the forestland before the extensive forest fires. There were about 40 % of ripening forest stands and up to 10 % of mature and over mature forest stands of the total forested area. The age ratio of plantation has changed a little after fires, however, old-growth plantations over 110-130 years old has failed. The number of plant species in the long-term non-burning forest areas is significantly higher than in burnt areas, logged lands and pine crops. The index of species abundance accumulation is higher in logged lands and plantations without burnings. The index of rare species have decreased from 1.25 (long-term non-burning plantations) to 0.25 after fires. The share of adventive plant species as well as plants native to steppe communities had increased in burnt areas. As a research result, it was established that forest fires led to a significant decrease in forest cover, area of long-term non-burning forests, unique plantations of woody plants, species diversity, indexes of species abundance accumulation and rare species, the share of plant communities in forest species and colonization of plant communities in burnt areas by alien species. The results of the work can be used in assessment of the impact of climate change and fires on biological diversity of forest communities in the region, development of measures for biodiversity conservation, planning of forest thinning and reforestation, etc.