I knelt down next to the big stump's remains, curious about its story. I wondered what species it was, what caused its demise, and how old it might be. It was a large stump, much larger than the trees growing nearby. My tape measure told me it had a ground-level diameter of 64 inches. That eliminated many tree species of the area—ironwood, black cherry, paper and yellow birch, aspen, red maple, bitternut hickory, butternut, black and green ash, black and white spruce, balsam fir, jack pine, and tamarack. They simply didn't reach that size.
Noticeably absent from the stump was its outer bark. Knowing that it takes at least 5 to 10 years for a tree to shed its bark upon death, I knew this wasn't a recent casualty. It was also covered in moss and shield lichens, an indication this stump was quite old, with sufficient moisture for their growth. Shield lichens spread radially at a rate of mere millimeters per year, indicating that this stump may have been exposed for several decades. Many trees rot too fast to allow for lichens and moss to envelop their stumps like this. Generally, other than oaks, black cherry, hickory, and ash, Minnesota's deciduous trees rot away completely within 30 to 40 years. This reduced the likelihood that this was a basswood, sugar maple, or elm—deciduous trees that could potentially reach this size. Cottonwoods and willows can also reach this size, but this wasn't the right habitat as those trees are prone to growing in floodplains and swamps.
Examining the stump more closely, I noticed that it was generally flat on top, with a handful of lichen-covered spires of uniform height rising in a cluster near the center. This told me the tree was cut down by a saw, because only with a saw will a stump be flat. Natural causes of death like windfall, disease, lightning strike, or fire will result in jagged, uneven trunk rotting.
Another clue was the absence of coppiced trees around the trunk. This informed me either that the tree was likely dead when it was cut, or that it was a conifer. Often when a live deciduous tree is cut, nodule buds on the trunk below the ground will sprout, sending up a ring of shoots around the parent stump. (On some older hardwoods like red oak, though, this isn't always the case.)
Also providing a hint were the spires in the center of the stump. Most hardwoods, such as maple, birch, elm, and aspen, have woods that rot uniformly. Conifers, with the exception of northern white cedar, rot from the outside in. Knowing that white cedars reliably grow in wet, low-lying areas or barren, rocky outcrops, neither of them present here, and that I have combed these woods dozens of times and never found a single cedar, I eliminated cedar as a candidate. That narrowed my range of likely trees to Minnesota's two largest conifers, white and red pine, as well as red oak, which doesn't decay in any particular order and whose stumps can persist for 75 years.
I scanned the forest and saw the canopy was composed of sugar maple, red oak, basswood, and big-tooth aspen with an understory of ironwood and balsam fir, and I knew that I was in a northern hardwood stand with soil that held moisture. Certainly this could be a massive red oak stump, as evidenced by the existing presence of red oaks in the canopy. This was not a landscape that would be dominated by red pines, which prefer dry and sandy soils, but it wouldn't be impossible for them to grow here. Was there another clue that could help point me in the right direction?
My answer came in the form of another tree. On the north side of the stump grew a yellow birch. One of my favorite characters of the forest, yellow birches occupy a remarkable niche in the north woods. Their tiny seeds are often too small and light to penetrate the duff layer of the forest floor. But moss on a stump provides a damp, spongy surface that reliably holds yellow birch seeds and provides the perfect habitat for their germination. Over time, the parent stump rots away and the yellow birch roots are left surreally suspended in air, as this one was. Yellow birches sprout from the nurse stumps of spruces and white pines. With this final clue in hand, I had arrived at one likely conclusion, that this stump was a white pine.
The setting for this discovery was the Audubon Center of the North Woods, a nonprofit environmental learning center near Sandstone in west-central Pine County. The county's name was appropriate when it was formed in 1856. Historical photos show a landscape covered in pines over 100 feet tall and 3 to 4 feet in diameter, but nearly all the pines succumbed to the crosscut saw in the 1880s and 1890s. This unfettered harvesting left branches and crowns, known as slash, 4 to 6 feet high on the ground across the region—a tinder box that ignited during a severe drought in 1894. The resulting conflagration burned at least 350,000 acres and created fire whirls—spinning columns of flames—so high that residents of Mason City, Iowa, saw them on the horizon more than 200 miles away.
That fire came through here, charring this stump and greatly slowing its decay because charred wood resists decomposition. It is because of that fire that I can still examine this stump nearly 130 years after it was cut, in a forest that no longer resembles the forest that once was. The current canopy of maples and oaks, absent white pines, is the result of the loss of white-pine seed sources due to intensive logging, a lack of frequent ground fires that clear off the duff layer exposing the bare mineral soil crucial for germination, and an influx of white-tailed deer that eat young pines.
Other pines next to the lake, having been spared the ax and the fire, offer a picture of what this majestic tree would have looked like. A white pine of this size would likely have been more than 200 years old, putting its germination at least back to the 1600s. I marveled at the stump as I realized this tree began growing long before our country was formed.
Looking around me, I saw another hint to this place's story—a nearby mound about 6 feet across, 4 feet wide, and 2 feet tall. It was covered in vegetation similar to everything else around it, but it was an obvious outlier from the immediate topography. The ground to the west of it was relatively flat, whereas to the east the ground was marked by a large depression. The depression, of nearly the same size and inverted height of the mound, told the story of another disturbance to the landscape. One fateful day, a powerful windstorm created enough strain on a large tree—possibly a white pine or a big-tooth aspen—that it toppled the tree in the direction of the blowing wind, ripping a mass of roots and soil from the ground and leaving a depression on the windward side. Over many decades the trunk, branches, and roots rotted away, leaving no trace of the tree, but the soil in the root mass remained, creating the pillow I now saw.
Ever since the ice sheets melted away 11,000 years ago and trees migrated into the area, this has been happening. As I looked around, I saw pillow after pillow dotting the forested landscape, all of them markers of storms from centuries past and records of nature's occasional fury.
This landscape and every landscape are reflections of all the conditions they endure. They respond to each stimulus, and each landscape depicts the constant saga of disturbance and succession. This yin and yang are what give us diversity in ecosystems. In general, the pioneering march of lichens is followed by grasses and forbs, which in turn are overtaken by shade-intolerant shrubs and trees, followed by shade-tolerant shrubs and trees. It is through the always-changing assault of storms, diseases, animal browsing, temperature extremes, drought, fire, and human disturbances that this successional cycle is interrupted and starts again.
It's only natural that we as humans try to understand what is around us and why, as our species' entire existence has depended on it. It gives context to the land and fills in the narrative of the landscapes of which we are part. Reading the landscape around me, I feel much closer to it as I picture the events that shaped it into what I see today. By slowing down, observing the character and patterns of a landscape, and simply asking "Why is this the way it is?" we can begin to read the fascinating, always changing story of a landscape. I know of few better ways to gain a sense of place.
