Long-tailed vole (Microtus longicaudus) population outbreaks and refugia after clearcutting of coniferous forests: The search for fluctuations and hotspots

Long-tailed vole populations increased in abundance on newly clearcut sites and reached independent peak numbers (62, 96, and 134/ha) at 3-4 years post-harvest in three different areas and time periods, thus supporting H1. Long-tailed voles were consistently at very low numbers in uncut forest, and hence this habitat did not provide a refuge or source area for voles, thereby supporting H2. We had some evidence to support H3 that long-tailed voles seemed to persist at low numbers (<5/ha) in riparian refuge sites. Where both species of voles were present, results tended to not support H4. We conclude that M. longicaudus did not have a multi-annual population fluctuation in abundance, at least for the 9- to 11-year periods post-harvest that we investigated. Thus, tree mortality from an outbreak population of M. longicaudus, occurring at 3-4 years post-harvest, could be avoided by planning regeneration planting after this single peak population has subsided. Some long-tailed voles may persist past the peak population in, or near, riparian sites. These voles did not occupy old-growth forest, and hence they presumably migrate to new clearcuts via road networks facilitated by linear grass-dominated habitats.