The ecological legacy of the mountain pine beetle in the southern Rockies: forest change and disturbance interactions
Date
2014
Authors
Perovich, Carlyn, author
Sibold, Jason, advisor
Hobbs, N. Thompson, committee member
Jacobi, William R., committee member
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Abstract
Mountain pine beetle (Dendroctonus ponderosae; MPB) outbreaks are naturally occurring ecological disturbances in western North America, but the last two decades have seen eruptions of unprecedented severity and extent. These outbreaks have created novel conditions in lodgepole pine forests that have historically had disturbance regimes dominated by large, stand-replacing fires. Previous research has found that MPB outbreaks increase relative abundance of non-host species. I use the lodgepole pine forest on the west side of Rocky Mountain National Park to examine mechanisms in this predicted forest change and the ecological legacy of the mountain pine beetle outbreak, particularly in terms of its implications for future disturbances. The recent mountain pine beetle outbreak increased spatial heterogeneity of species composition as a result of spatial variability in mechanisms of post-outbreak forest composition. Post-outbreak variances of up to 5 times greater and patch sizes up to 7 times smaller than pre-outbreak conditions. The increase in species heterogeneity will inhibit future landscape-level bark beetle outbreaks, though projected increases in Engelmann spruce and subalpine fir may make post-MPB forests more susceptible to other disturbances, including drought and fire. The MPB outbreak has increased landscape asynchrony, which will increase resiliency to future disturbances. However, this heterogeneity is a result of more spruce and fir on the landscape, species which are less adapted to projected future climate conditions.
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Subject
bark beetles
regeneration
forest
disturbance