Postpyrogenic digression of forest ecosystems in the mountain Cis-Baikal region

Abstract

The results of long-term studies of the role of the pyrogenic factor in the dynamics of forest ecosystems in the mountain Cis-Baikal region are considered. The consequences of surface fires in the full range of their intensity, from weak to extremely strong, are analyzed. The damage characteristics in pine and larch stands, differentiated by the types and degrees of fire impact, were obtained: burning and drying on stems, death of crowns with weakening the viability of trees, anomalous thinning. Fire scars on the surface of the tree stems, as an indicator of the degree of fire impact, serves as an external diagnostic sign of the post-fire condition of specific individuals. The higher on the stem fire scars are, the greater part of the tree was exposed to harmful thermal effects. But due to the variability in growth expressed in forest stands, trees differ in their reaction to such impacts. Young Scots pine Pinus sylvestris L. and the Siberian larch Larix sibirica Ledeb. tree stands are largely damaged and, as a rule, die after the exposure to medium-intensity fires, and at the age of 10-15 years even die after low intensity surface fires. The most vulnerable to fires are tree species with thin bark, such as Siberian stone pine Pinus sibirica Du Tour, Siberian spruce Picea obovata Ledeb., Siberian fir Abies sibirica Ledeb. and flat-leaved birch Betula platyphylla Sukacz. It is noted that 100-120-year-old Siberian stone pine stands are largely damaged by low-intensity surface fires, and are completely damaged after intense surface fires. The quantitative indices of liquid and solid surface runoff at the burnings are given. Mathematical models for the formation of liquid surface runoff and associated erosion of soils on burned areas are proposed, depending on the main factors affecting the development of these processes. The pyrogenic destruction of forest ecosystems inevitably results in the degradation of mountain soils, the restoration of which after surface fires takes many decades.

Keywords

• pine-larch tree stands
• surface fires
• destruction
• surface liquid and solid runoff
• Baikal region