Partial harvesting of dry Douglas-fir forests: Stand structure, range habitats and maintenance of biodiversity using small mammal indicators

Abstract

Our study used 'stand structures' and 'ecological indicators' as inferences to managing dry Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) forests for timber, biodiversity and range habitat attributes at 10-12 years after partial harvesting. Forest structures included densities and sizes of Douglas-fir and species and structural diversity of total conifers. Ecological indicators included cattle forage species in the understorey vegetation and three small mammal species: a closed-canopy specialist, the southern red-backed vole (Myodes gapperi Vigors) and two early successional species, the long-tailed vole (Microtus longicaudus Merriam) and heather vole (Phenacomys intermedius Merriam). Harvesting treatments were across a gradient of historical cut, individual tree selection and patch cut sites in the upper Interior Douglas-fir (IDFdk) biogeoclimatic zone near Summerland, British Columbia, Canada. Small mammal populations were sampled from 2006 to 2008. Closed-canopy forest structure seemed to maintain populations of red-backed voles in the harvested sites. Development of understorey vegetation in harvest-origin openings was similar across the levels of partial cutting and provided at least five plant species for cattle forage. Patches of grassland and shrubland in all treatment sites maintained viable populations of long-tailed voles and heather voles. These three small mammal indicators represent both late and early successional conditions in these IDF forests, which need to be managed for multiple objectives. Long-term monitoring of indicators will verify relationships with the components of biodiversity that they represent. © Institute of Chartered Foresters, 2011. All rights reserved.