Productive yet wild: Reconciling timber harvesting and small mammal conservation via understory protection harvesting in managed boreal landscapes of Alberta, Canada

The intensification of forest management demands innovative strategies that reconcile timber production with biodiversity conservation. This study evaluates the ecological effectiveness of Understory Protection (UP) harvesting, a spatially explicit method designed to minimize understory conifer damage, compared to Natural Disturbance Harvesting (NDH), where such vegetation is typically lost. Using a randomized block design, we deployed motion-triggered camera traps at 57 blocks representing four forest treatments: NDH, Unharvested forest (OG), and two UP sub-treatments: structurally intact UP_Buffer and more exposed UP_Trail. NDH and UP_Trail treatments, characterized by reduced canopy cover, green tree basal area and elevated grass cover and shrub density, favored both early-seral specialist and generalists such as Sorex shrews, Peromyscus maniculatus, Zapus princeps, and Lepus americanus. In contrast, UP_Buffer and OG treatments, characterized by late-seral structural conditions, supported greater habitat use intensity and higher naïve occupancy by old forest specialists including Clethrionomys gapperi, Glaucomys sabrinus, and Tamiasciurus hudsonicus. Notably, Clethrionomys gapperi and Glaucomys sabrinus occurrence was insensitive to time since harvest, indicating structural retention, not stand age, was the key predictor of their presence in the range of conditions measured. These results suggest that UP harvesting supports a diverse small mammal assemblage by integrating complementary habitats (UP_Buffer and UP_Trail). Critically, the within-stand heterogeneity established by UP_Buffer accelerates ecological recovery toward old-growth conditions, rapidly providing habitat for old forest-associated species in managed boreal forests.