Regional moose (Alces alces) responses to forestry cutblocks are driven by landscape-scale patterns of vegetation composition and regrowth

Abstract

Forestry activities are globally widespread and can have a large positive or negative influence on wildlife. Wildlife responses to forestry cutblocks (defined areas where trees were harvested) vary as a function of forest succession, which differs across systems. Across their distribution, moose (Alces alces) and forestry are often closely associated. Moose are predicted to select for cutblocks because of greater browse quantity in early successional vegetation, but moose responses to cutblocks are inconsistent across studies. Our objective was to compare moose spatial responses to cutblocks as a function of year since cut between study areas (Prince George South [PGS] and Bonaparte [BP]) while considering differences in vegetation composition and regrowth to better inform forestry planning in British Columbia, Canada. We characterized cutblocks by dominant tree species as a proxy for vegetation composition and estimated the normalized burn ratio (NBR) from multispectral satellite imagery as an index of vegetation regrowth (i.e., structure). We then examined the use of cutblocks by moose dependent upon vegetation composition and NBR using generalized additive mixed effects models. Next, we used locations of collared moose and nearby available locations to examine moose responses as a function of year since cut and used those responses to group cutblocks into age classes, which were incorporated into resource selection functions (RSF) to compare moose responses between study areas. Vegetation composition differed between study areas, and although cutblocks in both study areas followed similar regrowth trajectories, NBRs for cutblocks > 13 years post-logging in PGS exceeded those in BP. Moose demonstrated greater use of locations within cutblocks with intermediate NBRs and dominanted by spruce (Picea engelmannii × glauca) versus Douglas fir (Pseudotsuga menziesii var. glauca). Moose responses as a function of year since cut varied seasonally, but across seasons, moose tended to avoid new cutblocks (1–8 years), select for regenerating cutblocks (9–24 years), and avoid older cutblocks (25–40 years). In both study areas, RSFs revealed that moose avoided new cutblocks, but moose in PGS were more likely to select for regenerating cutblocks in comparison to BP. Our analyses suggest that the use of cutblocks by moose is a function of year since cut, vegetation composition, and vegetation regrowth, likely resulting from differences in browse quantity and lateral cover. To maintain stable moose populations, managers should consider vegetation composition and regrowth during forestry planning, and future research should focus on identifying region-specific forestry thresholds for moose.