Recovering from the storm
of the century
By Greg MacCormack

OTTAWA — The ice storm of 1998 is remembered as the worst ice storm on record. Trees were damaged across Ontario, Quebec, and the Maritimes as well as the northeastern United States.

Ontario was pelted with 85-110 millimetres of freezing rain that would wreck the maple syrup and wood lot industries. These industries, like the trees they depend on, are only now recovering from the storm.

Canadan Forest Service graph of dammaged areas.

Forests damaged

Accumulated ice caused tree branches to bend and eventually break off. Larger branches near the top of trees crashed into branches below causing them to break with a distinctive snapping sound. Wade Knight from the Ontario Woodlot Association said the ice storm left many trees with a “brush cut” or crown damage. In some areas, the trunks of smaller trees snapped from the weight of the ice.

According to Thomas Knowland, a researcher for Natural Resources Canada, maps of damaged areas resemble a “checkerboard.” Small changes in elevation or exposure to wind created variations in tree damage, even in a small stand. Knowland says tree mortally doubled the year following the ice storm.

Ken Farr, a science advisor for Forestry Canada, said trees with a wide crown structure typically found in urban environments, had more damage than trees in forests. Forest trees grow more vertically and have less surface area where ice can accumulate.

Farr says various species of trees faired better than others. He notes that conifers, such as spruce or pine, were relatively unharmed since they evolved at northern latitudes where ice storms and snow are a common occurrence. Farr says they “fold up like an umbrella.”

Long-term damage

This tree suffered serious crown dammage.

Knight says trees take a long time to die — longer than we might think. The long-term damage that followed the storm was less apparent. The ice storm stressed trees and left them susceptible to infestation and disease and further extremes in climate.

Knight said a drought in 2000 further weakened trees and killed some that were already damaged by the ice storm.

How a tree dies

Knowland’s research shows that the amount of sugar stored in the roots remained at lower levels for three years following the ice storm. This lack of sugar slowed overall tree growth in the spring since plants survive winter on stored plant sugar or starch. Stored starch also provides energy for the formation of buds so leaves can form and provide new energy through the process of photosynthesis. Knowland says starch builds up through spring and summer reaching its height in the autumn just before a tree enters dormancy.

Ken Farr, science advisor to the Candian Forest Service.

Infestations can also threaten weakened trees. Farr says invasive species such as the Asian Longhorn Beetle and the Emerald Ash Bore are spreading despite the best efforts of the federal government. The Longhorn Beetle has been known to attack healthy trees in Canada, something it does not do in its native Asian habitat.

Farr adds damaged trees are also affected by fungi such as mushrooms and conks, which can grow in areas exposed by the loss of limbs. Conks are lingified or hardened fungi that resemble steps.

How a tree heals

A tree continues to grow after the ice storm.

Farr explains trees do not heal like humans. The area affected is compartmentalized — the tree will effectively stop sap and nutrient flows to the damaged areas, preserving nutrients for the undamaged parts of the tree.

The Cambium layer

The cambium layer, which grows just under the bark, will eventually grow over damaged areas to cover them up. This will make the tree less susceptible to infestation and disease.

Gaining new girth

Not all trees recover at the same rate. David Chapeskie, from the Great Lakes Forestry Service, says maple trees might take an additional four to six years to recover from the ice storm. Where as poplars, which grow much faster, recovered in only a few seasons.

He says some trees have not recovered because they have a set growth pattern, regardless of environmental conditions. Coniferous trees fall into this category. They only grow for a short period in the spring. Deciduous trees grow throughout spring and summer, with the exception of oak, which grows like a conifer.

The ice storm stunted trunk growth as well. During testing in the Eastern Ontario Model Forest, Knowland observed that it took four years for a tree to start adding to its diameter.

Branching out

Undamaged parts of the tree will grow new branches. Farr says sunlight reaches branches that were previously covered by upper branches. And when this happens, systems of “backup” buds that normally lie dormant are activated — creating new or epicormic growth. Seven years later, an urban tree might have an odd shape featuring a large twenty-year old limb with new shoots branching out vertically from the awakened buds.

Farr adds this new growth is most susceptible to additional loss since only a few layers of growth are holding the branches in place.

Trees that experts like Farr describe as “odd” will stand in silent testament to a storm that is often described as a once-in-a-century event. Perhaps Farr is correct when he said trees are more resilient than people give them credit for.

Money will grow on trees, eventually

The ice storm was an event that continues to be felt by people whose livelihood depends on trees. Seven years have passed and nature is still repairing the damage done by freezing rain. Some damage lingers on.

Experts disagree on when industries reliant on the forest will return normal. Once the trees recover, the industries that rely on them can recover as well. Knowland says research suggests that maple sap will return to pre-storm levels in two to three years, although this is subject to weather conditions which could affect the health of trees and their recovery. McLachlan says sap production may already be back to normal, since weather can have a large impact on sap production. Knight says it will take years for local wood lot owners to recover from the ice storm.

Souring the syrup industry

Nelson McLachlan, President of the Ontario Maple Syrup Producers Association, says the ice storm caused many problems. He says some owners in the worst hit areas resorted to turning their trees into lumber in an attempt to recover their losses. Other maple syrup producers were more fortunate and were able to keep trees in production, though at a reduced rate.

“Conservative tapping guidelines prescribing no more than two taps per tree, regardless of size, are recommended where the maple trees are under stress or have lost 25% or more of their live crown;” says Chapeskie in a 1999 article. “Trees smaller than 30 centimetres in size should not be tapped under these circumstances.” This reduces stress to the trees and allows large trees to remain in production. Another option used by maple syrup producers was to move their taps to trees that were not being tapped and that were not as damaged. However, sugar bush owners may not have enough undamaged trees to shift production to while they wait for their trees to heal.

An American researcher, Moore, concluded in 1951, “the volume and sugar concentration of the sap was related to crown depth, density and height. Trees with live crown ratios averaging 50 to 75 per cent of their total height yielded about 25 per cent more sap than similar sized trees with crown ratios less than 50 per cent. ” Knowland says low root starch levels impacted the quality of the sap in the maple trees. With less sugar in the sap, more sap is required to make syrup.

Wood lots Damaged For Years

This tree escaped serious harm

Wood lot owners lost thousands of dollars due to the ice storm. Knight says the storm harmed many trees before they could be harvested. He adds, trees are sold according to the length and quality of boards they can produce. Damage creates knots and causes the wood to discolour. These deformities can decrease the tree’s value dramatically.

Knight says many wood lot owners are “weekend warriors” and are still cleaning up after the storm. They continue to cut down dead trees and cart them away. Many of these trees are already decomposing and are worthless as lumber. The ice storm effectively thinned out a number of wood lots. The thinning out process normally allows the remaining trees to grow better with less competition maximizing the profitability of the wood lot. However, unlike a selective thinning, the storm damaged all of the trees to some extent.