Complex effects of site preparation and harvest on snowshoe hare abundance across a patchy forest landscape

Abstract

Maintaining forest biodiversity requires an understanding of how forest-dependent species respond to a variety of forestry activities. This is particularly true for mammals, which often act as keystone species or focal species for conservation efforts in forest ecosystems. Snowshoe hares (Lepus americanus) serve as an important herbivore and prey resource throughout their range in the boreal forest. We examined the response of hares to partial and clearcut harvest, site preparation activities (post-harvest burning or chemical/mechanical preparation for regrowth), and precommercial thinning, using pellet plots on 359 forest stands across an expansive landscape in northern Idaho over a 5-year period. Hares initially responded negatively to harvest, with clearcut harvest having a greater negative impact than partial harvest, and this response was exacerbated by site preparation activities. Mid-successional stands (15–40years old) that had been clear cut with site preparation treatments applied or partially harvested with no site preparations applied had greater snowshoe hare pellet counts than mature or recently harvested stands. Pre-commercial thinning had no detectable effect on hares in this landscape. Our findings suggest an interaction between site preparation and type of harvest (clear-cut vs. partial), which suggests that both the initial negative impacts and subsequent positive response to site preparation as stands age are attenuated somewhat in partially harvested vs. clear-cut stands. Our results likely relate to the influence of management activities on vegetative cover, which is strongly related to hare abundance in a variety of systems. They suggest that silvicultural activities such as site preparation could be damaging to hare populations when applied widely across landscapes, particularly when young age classes predominate. However, because the effects of harvest and site preparation are largely transitory, use of these techniques may not substantially depress hare populations if enough stands can be maintained in the 15–40year age class.