Colonization of storm gaps by the spruce bark beetle: influence of gap and landscape characteristics
Abstract:• After storm disturbances, there is a risk for degradation of the quality of fallen trees, and for subsequent tree mortality caused by the spruce bark beetle Ips typographus (L.) (Coleoptera: Curculionidae). Models assessing the risk for bark beetle colonization of different kinds of storm gaps would be a valuable tool for management decisions.
• The present study aimed to determine which gap and landscape characteristics are correlated with the probability of colonization of wind-felled Norway spruce trees by I. typographus.
• The study included 36 storm gaps, varying in size from three to 1168 wind-felled spruces, created by the storm Gudrun in southern Sweden in January 2005.
• In the first summer, on average, 5% of the wind-felled spruces were colonized by I. typographus. The percentage of colonized wind-felled trees per gap was negatively correlated with the total area of storm gaps within 2000 m in the surrounding forest landscape.
• In the second summer, the proportion of colonized trees increased to 50%. Both gap (mean diameter of wind-felled trees and basal area of living spruce trees) and landscape variables (amount of spruce forest) were significantly correlated with colonization percentage and explained almost 50% of the variation between gaps.
• There was no relationship between gap area and colonization percentage. This implies that landscapes with many large storm gaps, where logging resources will be most effectively used, should be salvaged first.