On Natural Distrubance in the Boreal Forest

Over most of the boreal forest in Canada, a disturbance regime “consisting of high-severity stand-replacing events” (above) predominates, with fire and insects being the major agents of disturbance. Harvesting is predominantly by clearcutting.

Many companies are now attempting to clear-cut in a manner that mimics the primary natural disturbance in the western boreal forest, namely, fire. As a result of fire, there is much variety in species and ages of vegetation in the Canadian boral forest. Recent Sustainable Forest Management Network research has found that fires have varied greatly in frequency and intensity in the North American mixedwood boreal forest over the last 6,000 years. The short fire cycles (50-100 year) are emulated by today’s cutting cycles, but longer fire cycles (300 years) are also “normal”. During short fire cycles, early successional species of hardwoods predominate whereas late-successional softwood species have predominated during the longer cycles. Maximum landscape diversity is found between these extremes.

To better approximate the variable results of forest fires at the stand and landscape levels and thus help maintain biodiversity, some companies are now modifying their clearcutting practices. Modifications include making cutblocks more curved and irregular in shape; leaving standing dead trees, small islands of live trees, and woody material on the ground; leaving old conifers as seed trees to improve genetic biodiversity. Equipment that protects small conifers for regeneration purposes is being used in Quebec and elsewhere. Senate Subcommittee on the Boreal Forest, 1999

An introduction to Canada’s boreal zone: ecosystem processes, health, sustainability, and environmental issues
J.P. Brandt et al, 2013 in Environmental Reviews, 2013, 21(4): 207-226. The introductory paper is followed by a suite of papers dealing with various aspects of Canada’s boreal forest.

Natural Disturbances in Canada’s Boreal Forest (Video)
Natural Resources Canada, 2010 Fire and insects are the major agents of disturbance in Canada’s boreal forest.

Harvesting the Boreal Forest (Video)
Natural Resources Canada, 2010 illustrates the view that clearcutting emulates the Boreal Forest NDR, while acknowledging that patches of residual unharvested forest need to be left for wildlife.

Natural disturbance emulation in boreal forest ecosystem management — theories, strategies, and a comparison with conventional even-aged management
imo Kuuluvainen and Russell Grenfell Canadian Journal of Forest Research, 2012, 42(7): 1185-1203.

Forest Management Guide for Natural Disturbance Pattern Emulation Version 3.1
Ont. Min. Nat. Res.,Queen’s Printer for Ontario, Toronto. 40 p. 2001