Acceleration of Forest Structural Development for Large Trees and Mammals: Restoration in Decades or Centuries?

There is a demand for more progressive restoration directives to regenerate forest ecosystems impacted by harvesting, wildfire, insect outbreaks, and mineral resource extraction. Forest may take many decades even centuries without active silvicultural intervention grow large trees that provide suitable habitat various wildlife species. We tested the hypotheses (H) that, compared with unmanaged (unthinned old-growth) stands, large-scale precommercial thinning (heavy <500 stems/ha) of young lodgepole pine (Pinus contorta var. latifolia), at 20–25 years post-treatment, would enhance: (H1) architecture overstory (e.g., diameter, height, crown dimensions); (H2) mean (i) total abundance species diversity forest-floor small mammals, (ii) tree squirrels; (H3) relative use mule deer (Odocoileus hemionus). were three levels densities crop trees/ha: 353 (low), 712 (medium) 1288 (high), an unthinned, old-growth stand replicated areas in south-central British Columbia, Canada. Mammal measured during period 2013 2015. Mean diameter was significantly different among stands low-density, medium-density, having diameters larger than high-density unthinned stands. height highest volume low-density 2.1 5.8 times higher high-density, hence partial support H1. mammals 1.9 2.4 other treatment abundances per red squirrel (Tamiasciurus hudsonicus) (range 4.8 12.0) northern flying (Glaucomys sabrinus) 3.2 4.3) similar but variable counts pellet-groups/ha thinned 3.8 4.2 2.3 respectively. Thus, H2 supported, squirrels not. Enhanced not supported. To our knowledge, this first concurrent measurement several mammal heavily thinned, across replicate study post-treatment. Although all responses significant, there strong indication restored forests via heavy (<500 trees/ha) produced (at least dimensions) 33 42 old. Comparable albeit greater merchantable volume, ranged from 120 167 age. Restored capable supporting these be achieved rather centuries.