By Lisa Boonstoppel-Pot
Ash borer is just the start of future forest decimation with hemlock, butternut and beech trees also facing serious threat, concluded a forest study conducted by the Maitland Valley Conservation Authority (MVCA) as it was revealed 20 per cent of forest in Huron County is made up of standing deadwood.
“When you are walking in the forest, you have a one in five chance of putting your hands on a dead tree,” said Erin Gouthro, a watershed ecologist with MVCA who spoke on forest health at a meeting focused on forest health trends hosted by the Huron County Water Protection Steering Committee and Sustainable Huron in Clinton on November 25.
“This isn’t going to end with the ash borer,” added Gouthro in a presentation that had a doomsday knell as she outlined the declining diversity in the forest canopy. However, she did reveal tree size is larger in many woodlots and forest management practices do increase the health of forests.
Her goal, she said, is to “raise the signals” about the health of forest ecosystems before deciding what the next approach will be.
She and professional forester-in-training Matthew Shakespeare explained how the intensive two-year forest study was conducted and what it revealed. Forests are generators of basic human needs such as air, climate, soil and water. Forests are also reservoirs of biodiversity.
Both upland and lowland, along with private and public woodlots were surveyed to answer questions about diversity, regeneration, structure and disturbance. What is the health of the forest? What are the current challenges and how can forests be improved? Gouthro and Shakespeare learned that 86 per cent of Huron County’s natural areas are forests which translates into a 16.04 per cent (526.6 square kilometres) forest cover over the county (2020 numbers). That is a decline from 16.5 per cent (538 square kilometres) in 2000.
Maple trees are, by far, the most abundant species making up 41 per cent of all forest trees. Standing deadwood is 19 per cent, ash is nine per cent, pine six per cent, other coniferous are nine percent and other deciduous (including black cherry, American elm, yellow birch, American basswood, trembling aspen, American beech) make up the rest.
Before settlement, hard maples were a dominant species but so were American beech, elm and hemlock. Ash, on the other hand, wasn’t a dominant pre-settlement tree. Tracking species populations over time was an interesting part of the study and revealed how ash and soft maple began to dominate the landscape after settlement before ash was decimated by the Emerald Ash Borer.
In the wake of the ash decline, the study examined which seedlings are most dominant in today’s forest and discovered 61 per cent of seedling are ash, 18 per cent are sugar maple, seven per cent are red maple, six per cent are black cherry, two per cent are American elm and two per cent are Norway spruce. Invasive species such as glossy buckthorn and common buckthorn also had a large presence in the seedling count.
In terms of sustainability, size matters. A sustainable forest requires 50 metres square per hectare of trees. Tree size also matters. There needs to be more trees with a basal size (the horizontal area of trees 1.3 meters off the ground) over 15 metres square/hectare for a forest to be sustainable. There are more trees with a larger basal area in 2022 than in 2000.
“This is a good thing!” said Gouthro. “That tells us the management practices we put in place to decrease diameter cutting has a positive effect on the forests.”
More good news came from healthy trees versus stressed tree numbers. Of live trees scouted, 54 per cent were labeled healthy while 23 per cent were labeled stressed. Of those trees that were stressed, the most common reasons were insects, invasive plants, tree cutting and windthrows.
Gouthro and Shakespeare conducted three specific case studies:
Plot #1: This private maple and beech stand in East Wawanosh which had emerald ash borer and beech bark disease present. It had been logged at intervals. Concerns in this stand were the presence of glossy buckthorn, the infestation of beech bark disease and threat of beech leaf disease. The ash regeneration is threatened by the Emerald ash borer.
Plot #2: The stand of maple and ash had been logged at intervals and stem-wounds from logging were present, indicating poor forestry practices. Trees were smaller and the forest had been infiltrated with reed canary grass, multiflora rose, dame’s rocket, garlic mustard and common buckthorn. Trees had been uprooted by wind and killed by Emerald ash borer.
Plot #3: This maple and beech tree forest had not been logged had many windthrows and beech bark disease present. This forest had very low species diversity with three living tree species, two of which were dying from pest and disease. It has 59 per cent standing deadwood, from large, dead beech trees meaning this forest was releasing carbon rather than storing it.
“From these plots, we learned that not stewarding or managing forest puts the forest at risk,” explained Gouthro. “When forests are not stewarded, we risk losing them to invasive species and disease.”
Gouthro said monitoring is part of sustainability because threats to forest health can be identified via monitoring which leads to resolutions.
During question period, it was asked what the trajectory of the Emerald Ash Borer is and will it die out or sweep back through to kill younger ash trees. Gouthro said they simply do not know. It might sweep back through, taking down saplings, relegating future ash trees to being a shrub tree that never gets a chance to grow into large trees. Right now, Emerald Ash Borer leaves behind ash trees smaller than nine centimeters. However, it eats ANY size of black ash trees.
There are indications that three species of parasitic wasps released into Ontario forests might one day prove effective in controlling (but not eliminating) the ash borer.
During the forest study, Gouthro and Shakespeare also kept their eyes out for trees that are disease resistant. “We found some elms that survived and we are hoping they can throw seed and come back into the landscape, but that may take 200 years or so,” said Gouthro.
Now, the best path moving forward is active stewardship and management. “The disturbances that are here and coming are having a major impact,” concluded Gouthro. ◊