Stumps provide better access to the sunlight that is so crucial for seed germination and growth.
It’s no secret that much of Washington’s old-growth forest has been cut down. Walk through almost any forest and you’ll find slowly decaying cedar or Douglas fir stumps, often with springboard cutouts still visible. Oddly, but often, these monuments of what once was are also markers of what will be.
Every year, while millions of seeds battle for growing space in the forest understory, a few land atop an old log or stump and take root. The first time I observed this phenomenon, I saw a young hemlock stemming from a six inch Douglas fir stump which was sitting on a much larger Douglas fir stump! Clearly it’s just confused, I thought.
As I continued to explore, though, I noticed that not only was this hemlock not an anomaly, but also that in some forests, the only trees in the understory were those sitting on the old stumps!
Did they not need soil? Would they not fall when the stump rotted away? Wouldn’t their roots freeze? And if they could survive in these conditions, why can’t I keep my garden alive?
Well, it turns out there are good reasons such pedestals are perfect places to start new trees.
The tops of stumps typically sit above the base layer of ferns, mosses, and small shrubs, providing better access to the sunlight that is so crucial for seed germination and growth. And the decaying wood is a great substrate, providing a firm base with ample nutrients, better moisture retention, and less leaf and needle loading, which can smother seedlings buried under a thick layer on the forest floor.
Stumps also decay at about the same rate that they grew. A sapling on a 200-year-old cedar stump will have plenty of time to grow strong and support itself.
Next time you are in the forest, keep a lookout for these “nurse” logs and stumps. They help to showcase the amazing resiliency of the natural world!
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