Ecological Estimation of Forest Succession Patterns in Central Angara Region

Abstract

It is now widely recognized that the forests of the Angara region, as they look today, developed essentially under the influence of fires (Popov 1957, 1982; Krauklis 1975, 1985; Buzykin and Popova 1978). Fires are a common disturbance event and an important ecological factor in taiga forests. Over the last few decades, spatial patterns of forest communities, at different stages of post-fire succession, are undergoing complicated changes due to increasing forest resource exploitation. Intensive forest harvesting leads to a great increase of areas occupied by young stands. In most parts of the Angara region, fires and cutting cause the replacement of climax dark conifers by light coniferous and hardwood species. Relatively frequent surface fires destroy dark conifer regrowth and the subordinate (lower) wood layer composed of spruce, fir, and Pinus sibirica, thereby hamper their regeneration. Wide local variations in age structure, species composition, and productivity of southern taiga forests of the Angara region are attributed to the heterogenity of ecological site conditions and different patterns of fire occurrence and harvesting, which in turn determine specific microclimatic situations. Since regeneration processes after human-caused disturbances in fact obey, the same laws as natural vegetation succession, it is reasonable to study post-fire and post-cutting vegetation successions in the context of general vegetation cover dynamics.