Climatic conditions for emergence and flight of mountain pine beetle: implications for long-distance dispersal

A significant shift in the mountain pine beetle (Dendroctonus ponderosae Hopkins, 1902) range has been attributed to long-distance dispersal from the observed spatiotemporal patterns of beetle infestations in the recent outbreak in western Canada. However, long-distance dispersal is still the least understood aspect of mountain pine beetle ecology. In particular, the mechanisms responsible for the three major phases of long-distance dispersal, the ascent, transport, and descent, are poorly known. In this study, we used the North American Regional Reanalysis meteorological data (1999–2010) to determine climate conditions under and above the forest canopy during mountain pine beetle emergence and flight at the landscape scale. We found that climate conditions are distinct during emergence and flight. They provide an ideal underlying environment to facilitate the potential long-distance dispersal. Climate conditions are unstable under the forest canopy during emergence, which would help loft beetles above the forest canopy to initiate long-distance dispersal. The first direct evidence from wind directions above the forest canopy suggests that atmospheric transportation of mountain pine beetle in the planetary boundary layer is aided by wind.