Ips sexdentatus Börner damage in Siberian pine-dominated forests of southern Central Siberia

Abstract

The subject of this study is an active outbreak of the six-toothed bark beetle (Ips sexdentatus) in the Manskoye forest management unit of Krasnoyarsk Krai (Altai-Sayan mountain-taiga forest region). The objective of this study is to evaluate the impact of the bark beetle on the deterioration of forest stand health and sustainability, particularly in stands dominated by Pinus sibirica. The research methods employed included forest pathology monitoring, an integrated assessment of stand health, the visual detection of damage to Siberian pine by the six-toothed bark beetle using standard indicators, and a statistical analysis of empirical series of tree distribution by diameter. The health of forest stands, including Siberian pine, has been severely weakened, with the current-year mortality rate representing a medium-to-severe degree of disturbance. The damage to Siberian pine in the bark beetle outbreak area is from weak to severe with a predominance of trees that have already been damaged and left by the bark beetle. The share of the stem volume of inhibited trees is less than 10%. The bark beetle colonizes trees of any size in proportion to their representation in the stand structure. In the six-toothed bark beetle outbreak area, the majority of trees exhibiting signs of damage are dead. The average health category of affected trees is classified as dying-dead. The proportion of inhibited living trees in the 2-3 health classes was 14-19%, indicating an increase in the aggressiveness of the xylophage. This is due to the high numbers of the xylophage in combination with preliminary violations of the resilience of forests due to anthropogenic activity and negative changes in site conditions.