The year 1969 was historical for many. Movie fans were treated to would-be classics such as True Grit and Butch Cassidy and the Sundance Kid. Music lovers swarmed upstate New York for a weekend concert event that was dubbed Woodstock. Neil Armstrong journeyed where no man had gone before and uttered the now famous line, “That’s one small step for man, one giant leap for mankind.” For northern Minnesota, it was Aug. 6 that made history. It was one of the worst tornado outbreaks in Minnesota - a dozen tornados were recorded that day. The most destructive and powerful was an F4 that started near Pine River and moved east for 32 miles passing over the town of Outing and clipping the northwest corner of Aitkin County. F4 tornados will have winds up to 200 miles per hour. The series of storms that day killed 15 people and injured 109.
In the wake of the storm was a trail of mangled timber, twisted tree tops, and exposed root balls. Many wondered how such a mess could be cleaned up and salvaged. Others observed the tangle as a huge wildfire risk. However, Mother Nature thought nothing of it. This is her way of regenerating trees and it has been going on since the beginning of time. The resiliency of our forests is often forgotten and overlooked. Mother Nature always seems to find a way to heal the landscape after disasters such as tornados, floods, and fires. In fact, much of the forest management land managers do today mimics what Mother Nature does.
As forests grow and evolve through time, they go through stages of succession. Immediately after a disturbance, the site quickly becomes dominated by ‘pioneer species’. These are typically fast growing, short-lived trees species that need full sunlight in order to grow. The most common pioneer species foresters manage for are aspen and paper birch. Fast forward 50 years and that same stand of aspen is beginning to break up. Insect and disease damage coupled with old age marks the start of another stage of succession. As the trees die, long-lived, slower growing trees that can survive in the shade begin to emerge. This would include species like sugar maple and basswood. Once at this stage, sugar maple and basswood can dominate the site for thousands of years. To bring pioneer species back to the site, the succession cycle needs to be reset.
In 1969, it was a tornado that reset these forests. Once the overstory trees were removed, the forest floor was exposed to direct sunlight. This spurred the establishment of aspen. In fact, if you go back now to the areas hit by the tornado, you will find vast stands of 50-year-old aspen. Although some areas were planted to red pine, the majority of the area affected by the storm is now dominated by aspen. Modern day logging is the mechanism used today to create disturbance and set back the forest succession cycle. Without logging, our aspen forests would eventually succeed into sugar maple/basswood forests. Sugar maple/basswood forests are an important component to the landscape, but so too is aspen. A healthy landscape that supports an abundance of wildlife and forest products is one that contains a variety of tree species and age classes. Diversity is key.
It is said that imitation is the sincerest form of flattery and in forestry, many of our logging practices are designed to imitate what Mother Nature does. But as Francis Bacon wrote, “Nature, to be commanded, must be obeyed.” That said, foresters do have the advantage of being able to control the size and intensity of the disturbance.
Dennis Thompson is a assistant land commissioner with the Aitkin County Land Department.