Forest Fungi Research: Fighting a Hidden Enemy

By Carolyn Grey
March 2011

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Internal butt rot of pre-commercially
thinned balsam fir

Hidden beneath seemingly healthy balsam fir stands, forest fungi launch an attack on the trees’ base and roots, causing slow and silent damage. What is this pest that is wreaking such devastating damage — known as root and butt rot — among balsam fir, as well black and white spruce?

Natural Resources Canada (NRCan) researchers with the Canadian Forest Service’s (CFS’s) Canadian Wood Fibre Centre (CWFC) in Corner Brook, Newfoundland and Labrador, are studying the possible causes and effects of root and butt rots in pre-commercially thinned balsam fir stands.


Detecting the Enemy
Part of the challenge in studying these fungi is their ability to go undetected, with no external signs that they are already causing tree damage.

“It used to be a long, tedious process just to isolate and identify these fungi,” says Gary Warren, Forest Pathologist at the CWFC. “Today, new tools using DNA molecular techniques have lead to a much more efficient process that greatly increases the speed and accuracy of fungal identification.”




Root of the Problem

Vials containing Coniophora puteana
(brown rot fungus).

Studies have shown that many factors play significant roles in the presence and severity of root and butt rot, such as tree species, the age of the stand, both at the time of thinning and at present; the intensity of thinning; and site conditions such as soil type, moisture, fertility, location and other factors currently being investigated.

“Our research is trying to identify the various factors responsible for the increase in root and butt rots and how these factors may affect the fungi responsible for the problem,” says Gary. “The aim is to reduce the loss of tree wood volume and to improve fibre quality.”


Yielding Interesting Results

Windthrow caused by butt rot in a balsam fir
spacing trial in north-western N.B.

Sites that are over-stocked with young balsam fir are sometimes thinned to encourage the trees to grow faster with less branches and straighter stems. But scientists have long wondered whether pre-commercial thinning increases the incidence of root and butt rot.

Early results show that, although thinning reduces competition and allows for better initial growth and form in balsam fir trees, the damage from root and butt rot is happening earlier. Accordingly, in order for forest managers to maximize the amount and quality of the fibre, trees may need to be harvested at an earlier age than originally planned.

An important part of this research involves determining current levels of fibre loss and assessing the future impacts of forest fungi. Although many of the major root and butt rot fungi have been identified, there are still many more unknown to forest science.

“With this research, the ultimate goal is to assist forest managers to get the best yield possible from this forest fibre resource,” concludes Gary.



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