Old White Spruce, Bark Beetle and Forest Succession on Cape Breton Island

Jamie Simpson

A few years ago I found myself tramping over a 400 acre woodlot in Cape Breton, hired by a family to provide advice on what to do with their forestland. None of the dozen or so family members wanted large-scale cutting, but beyond that opinions ranged from ‘just let it be’ to ‘but we have to do something’. Oh, and what about fire risk with all the dying spruce? I quickly realized my role was part forester, part mediator. The family’s key question was what to do with the patches of mature white spruce growing on old pasture land. As with almost all of eastern Nova Scotia, the white spruce were in various stages of decline due to the bark beetle.

As it happened, the family’s woodland provided an interesting case-study in forest ecology, particularly in forest succession. To set the stage a little, about half the property was covered with mature hardwood forest typical for the site: mostly sugar maple, beech and yellow birch. The other half had been farmland, let go to forest at various times over the past half century or so, and had grown back with mostly white spruce mixed with bits of red maple, fir and white birch. Some patches of white spruce had been clearcut 15 years ago, some patches were still reasonably vigorous, and some were well along the path to falling apart.

The patches of falling down white spruce told a rather interesting story of rapid forest succession in action. Pretty darn exciting, I know. As shown in the accompanying photos, seedlings of sugar maple, yellow birch, white ash and beech were well established wherever enough trees had died to allow partial light to reach the ground. Some of the young hardwood were already reaching over my head. These old-field white spruce stands were well along a transition to shade-tolerant mixed hardwood stands.

As I walked along I thought about why the sugar maple and yellow birch seedlings in these areas were growing so well. Anyone who plants hardwood knows that they can be tricky to establish. One plus was the moderate microclimate that the dead and dying spruce provided: not too sunny, not too shaded, not too hot, not too dry. The other plus, I surmised, was that the tangled mess of fallen spruce provided a physical barrier to browsing deer. Interested in this theory, I searched the scientific literature and, sure enough, found a study confirming that a mess of tree tops and branches left on the ground after harvesting helps protect seedlings from hungry deer.

So, what did I tell the family? In my report I explained that white spruce was not the natural forest cover for their land; while the bark beetle is hastening its decline, white spruce wasn’t destined to survive much longer on their land anyway. I suggested that they could indeed do some limited harvesting of some of the still-living white spruce to provide logs for their building projects, and that they had lots of potential to harvest firewood from the hardwood stands. Where the white spruce was already too far gone, I told them no need to worry, because the dead and dying spruce were nurturing the next forest – don’t lift a finger, and enjoy watching a new mixed hardwood forest grow, a forest much better suited to their property. In time, they may consider doing some pre-commercial thinning to help encourage tree species that would be common in old forests, such as sugar maple and yellow birch.

Some might suggest that the property should be “sanitized” by clearcutting to address the bark beetle problem. While such cutting might help to temporarily reduce the local population of bark beetles, it would not do much to stem the bark beetle infestation on a regional scale. The cause of the bark beetle outbreak is the un-natural abundance of mature white spruce across eastern Nova Scotia; the bark beetle problem won’t be solved until these white spruce forests evolve into new, more diverse forests that are less vulnerable to bark beetle.

As for fire danger, I explained that heavy tree-cutting would actually increase fire risk for their forest by putting a large amount of tinder-sized branches close to the ground, without any shade to keep things moist. As well, the fine branches of the dead and dying spruce (the material that adds to the fire danger) fall to the ground gradually, and are quickly decomposed, thereby avoiding a large build-up of dry branches close to the ground. As the young hardwood trees grow, they provide additional shade, thereby keeping temperatures down and moisture levels up, warding off fire hazard.

The areas on the property where white spruce had been clearcut some 15 years previously also told an interesting story. A few scattered young hardwood trees had grown in the clearcut, but were in rough shape. They were heavily branched due to lack of shade and stunted by repeated animal browsing.

With my report in hand, the family and I walked parts of the woodlot so they could see for themselves my key findings. Fortunately, all members of the family felt that their concerns and wishes for the property were respected: there was no need for drastic measures to reduce fire hazard or to renew the forest, but there were also ample opportunities for limited harvesting to meet their lumber and firewood requirements. A few years from now, I look forward to walking this family’s property again to see how their forest, and their understanding of their forest, evolves.

4 comments
  1. gifford1949 said:

    This is a great story Jamie!

  2. David Blackwell said:

    Enjoyable and enlightening reading as so much of what to say here is. I presume O.K. to share with others (including internationally).

    • Hi David – thanks so much for the good words here. And yes, please do share if you wish. All the best, Jamie

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