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Ecol. Forestry & Conservation
DRAFTING
Also view on this website: Natural Disturbance Regimes
– How logging left Atlantic Canada’s trees vulnerable to Hurricane Fiona
By Haley Ritchie in the Narwah, Nov 22, 2022 “A century of overplanting money-making species helped Fiona ravage east coast forests. Can woodlots bring back biodiversity while also turning a profit? “..the Maritime forest has changed a great deal since the time that the members of the Wabanaki Confederacy — including the Mi’kmaq, Maliseet, Passamaquoddy, Penobscot and Abenaki — were stewarding it. Old-growth forests have been cleared for agriculture and heavily logged: according to the Nova Scotia Nature Trust, only 0.6 per cent of the province’s forest is over 100 years old. And replanting has usually meant focusing on a less diverse collection of species and ages than was here originally. That youth and homogeneity puts the region at greater risk during natural disasters. After Hurricane Juan, University of New Brunswick forest management professor Anthony Taylor led an extensive study looking at how forests are impacted by extreme winds.Published in 2019, the study used aerial photography and satellites to analyze how wind damage varied based on topography, weather, soil and forest structure. It found that having a greater amount of hardwood species and pine reduced the effect of wind damage to a lot or forest. Tall stands were most vulnerable, especially those dominated by shallow-rooted spruce and balsam fir. Unfortunately, the two most vulnerable species are also overrepresented in the region, as a result of their value for softwood lumber and pulp and paper. “Over the last century, we’ve been carrying out forest management practices that promote more spruce and fir,” said Taylor. “So by default in the forest, it’s already been a bit more vulnerable to blowdown, because we have much more of the spruce and fir.” Taylor’s study found that while forests dominated by a single species that had been replanted after a clearcut were hurt by wind, so were areas in mixed forests that were more selectively thinned. Both harvesting methods created vulnerabilities.“I don’t know if anyone has a solution yet, but it’s definitely on a lot of minds. If you believe the science and the projections of climate change, then we’re going to be in for more wind and it’s going to impact our forests,” Taylor said. “If we know that our spruce and fir forests tend to be more susceptible to wind, but we really depend on them for our economy here, then what do we do?” He also pointed out a caveat from the study — which suggested that regardless of species or topography, 10 minutes of sustained winds of 100 km/h can topple most trees. “At a certain threshold it doesn’t matter what your forest is made of — likely a lot of it is going to blow down,” he said…”
– Forest structure more important than topography in determining windthrow during Hurricane Juan in Canada’s Acadian Forest
Taylor, A. R., et al (2019). I Forest Ecology and Management, 434, 255–263. https://doi.org/10.1016/j.foreco.2018.12.026 Highlights
• Wind speed had highest influence over stand vulnerability to windthrow.
• Following wind speed, stand structure most important in determining windthrow.
• Tall stands dominated by spruce and balsam fir were most vulnerable to windthrow.
• Topographic exposure ranked low in overall influence on windthrow.
• Contrary to expectations, mesic soils were most vulnerable to windthrow.
– The Effects of Hurricane Juan on Managed Stands Commercially Thinned in Central Nova Scotia
Tim McGrath & Jan Ellingsen. 2009. NS Natural Resources Report FOR 2009-4, No.89 “Many commercially thinned (CT) stands in Nova Scotia were severely damaged by hurricane Juan in September 2003. Despite this it was observed that some commercially thinned stands were not impacted. In an attempt to determine whether stand conditions affected damage levels in commercially thinned stands, a survey was made in the winter of 2003/2004 with assistance from several Nova Scotia Forest Industry firms and the Nova Scotia Department of Natural Resources (NSDNR). A relationship was discovered to exist between the number of trees removed in the thinning, the slenderness of the trees and the wind damage. Stands with an average slenderness ratio of between 80-85 were damaged by Juan when removal levels exceeded 40% of the trees (30% of the basal area) . When stands had stouter trees with H/D ratios averaging between 70 and 75, tree removal levels could be up to 50% (40% of the basal area) before wind damage occurred.”
– The Growing Impact of Wind
Marlie Knowlton for Forest Nova Scotia “There’s no doubt that a changing climate impacts the forestry sector. From heavy snow and ice to droughts and wildfires, it can feel like we’re always trying to recover. The growing frequency of wind events is the latest to impact our forests. David McMillan of McMillan Forestry says, “Because we’re in a province that gets way more wind events, we’ve had significant blow down occur in the last two big winds that we had this winter. Those were not hurricane-rated winds. When you listen to the experts, they’ll talk about how Nova Scotia, PEI, we get 150 more wind events than New Brunswick or Maine.” While not always classified as hurricanes, high wind storms can cause severe damage, particularly in the form of blowdowns where entire sections of forests are felled by strong winds. Because Nova Scotia is, essentially, stuck in the Atlantic Ocean, McMillan says, “We’ve got to modify what we’re doing and come up with a model to manage our forests sustainably and ecologically in such a way that it’s hurricane-proof.”…
Woodlands shaped by past Hurricanes
By David Dwyer, Forester on www.novascotia.ca/natr/; originally published in Forest Times November 1979)