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| OFRI research technicians Mandy Roberts and Shane Stuart assess a wind-damaged site southwest of Kapuskasing, Ontario. |
Windthrow—when wind uproots or breaks a tree—is a common natural disturbance in boreal forests. Whether it happens depends on several factors, including how big a tree is, how healthy it is, how strong its root system is, whether it is growing by itself or in a group, and whether it’s growing on a windy site.
Resource managers grapple with two types of wind disturbance: severe wind storms that cause catastrophic windthrow, knocking down entire stands, and post-harvest windthrow, especially in partially cut stands in which the trees that were left behind fall down.
OFRI researcher Rongzhou Man and partners are studying both types of wind disturbance in boreal mixedwood forests in northern Ontario in hopes of improving forest regrowth. Their studies include the following:
- During a severe wind storm in 2006, aspen-dominated mixedwoods south of Kapuskasing suffered catastrophic windthrow. This event is allowing Man to study how various silvicultural treatments affect forest regeneration and vegetation recovery. Within the windthrow area, Man is comparing how well trees are growing back in areas left alone with those that are salvage logged (after one or two years) and planted (with and without tending). Salvage logging not only makes use of the wood but also reduces habitat for damaging insects such as bark beetles, which infest the windthrown trees but then move to nearby healthy forests. Researchers will compare results from the treated areas with tree growth and development in a nearby clearcut.
- Red Lake District staff are studying the effects of windthrow in the Whitefeather Forest, where trees in a 1,000 ha area of conifer-dominated forest blew down in 2007. Man’s role was to help design a study that would provide scientifically sound results. Here, too, researchers are interested in how the new forest grows back, both trees and other plants. They are looking at what happens when these areas burn and are left to grow back naturally compared with when they burn and are seeded with jack pine. Researchers will compare results from the burned and regenerated areas with those from nearby untreated areas.
- In a completed study, Man worked with partners to monitor wind damage following partial harvesting compared with that in a nearby unharvested mixedwood in northeastern Ontario. They found that all species were susceptible to wind damage; few live trees were damaged but more of those were in the partially harvested areas; and live trees fell mostly in the first year after harvest while
more dead trees fell during a major wind storm four years after harvesting. They concluded that wind may affect the viability and feasibility of future treatments in partially harvested mixedwood stands. For details, see Wind Damage in a Partially Harvested Mixedwood Stand in Northeastern Ontario (Forest Research Report 175), available from information.ofri@ontario.ca.
Results of these studies will provide a better understanding of how mixedwood forests change and regrow after windthrow and how to ensure adequate densities of crop trees following severe wind storms. For more information about this research, contact Rongzhou Man.
