Last week I found myself bushwhacking about an hour from a trail when I noticed there were purple rain clouds coming over the top of the adjacent mountain. Back home in Minnesota, you can see rain clouds hours away and have plenty of time to react. But when a dark-blue cloud suddenly peaks over a mountaintop in Colorado it’s too late to adjust your trip. I sat down and unzipped my backpack to grab my rain gear, but my hands searched in vain. A few hours away in my cabin sat my jacket, left behind.
Sometimes nature leaves clues behind. An ecologist I’ve gotten to know over the past few years has been working out ways to answer what type of plants made up the landscape of Wisconsin hundreds of years ago and how often a fire decimated them.
Dr. Beth Lynch answers these questions standing on a frozen lake in the middle of the frigid Wisconsin winter. Using an ice auger to create a hole in the ice, she leaves the ice fishing rod behind for a much larger tool: a huge soil core. By extracting the layers and layers of sediment from the lakebed, she is able to take a glimpse back in history.
She identifies different grains of pollen in the sediment to determine which plants dominated the landscape of Wisconsin’s past. When pollen is released from a plant, some of it is bound to end up in the lake where it descends to sit silently on the bottom. Similarly, charcoal from forest and prairie fires is thrown into the atmosphere, after which some will settle on the lakebed.
In the lab, Dr. Lynch first identifies which and how many types of pollen are in the soil to determine which plants were present — the more pollen from a particular plant, the more prevalent it was. When she runs into a layer of charcoal in the sediment core, it means a fire. Since sediment is deposited over time, she can use the depth of the sediment she is looking at to put a date on it. Using this data, she has reconstructed the natural history of the sands of Wisconsin.
As I zipped up my backpack, my two friends and I decided to continue our hike along the valley in the rain. As my t-shirt became polka-dotted from the raindrops, we pushed through a deer trail in thick willows until we glimpsed an unfamiliar color through the boughs of nearby conifers: the tin roof of a long-abandoned mining cabin greeted us as the rain plummeted.
Hurrying into the cabin, we found rotting wood and old boxes of food dominating the entire floor of the cabin. It hadn’t been lived in for quite some time. We discovered a tattered, weather-beaten notebook on the ledge of a desk. Opening it, we found barely-legible notes of visitors past who had taken shelter in the deteriorating cabin — a couple from the summer of 1984, a winter skier from the 90s — pages and pages of small stories and pictures. It was really something to read short words from complete strangers decades ago whom, like us, happened to stumble across the old cabin for a short time before continuing on their journey. After scribbling a short note ourselves, the rain stopped. We continued home, leaving the notebook of stories behind.
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