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What’s a Girdled Tree?

Whenever I’m leading a hike or even just talking with visitors in the nature center, there are always a few questions I find myself answering frequently enough that they stick in my mind. So, during a chilly hike through the fresh snow a few days ago, I stumbled upon the cause of one of these often asked questions: “Why is there a ring cut into some of the trees throughout the forest?”

To me this is the kind of question that begs for an entry in my nature journal, it’s the perfect subject o spark curiosity, make careful observations, and in this case, follow up with answers. But as much as I enjoy nature journaling outdoors, a growing cold breeze reminded me I could finish the project in the office, so I took some photos, made some notes about what I could see or feel and go to work in the warmth of the Nature Center.

Journaling About an Odd Tree

When I journal, I try to include at least three observational prompts: “I notice,” “I wonder,” and “It reminds me of.” These prompts are by no means the only things I could ask myself or write down, but they always help build a framework for my curiosity. Glancing back at this oddly cut tree, wrapped in frozen sap, the first thing I noticed was how deeply the ring was cut into the tree itself. This cut wraps itself around the tree in a slightly lopsided matter. The slice itself is roughly 1-2 inches wide and in some places nearly an inch deep, certainly deep enough to expose the raw wood underneath the bark.

But my eyes, and fingers, are drawn to the sap, frozen by the temperature, mid-drip down the side of the tree in off-white streaks. In warmer months, I’ve touched it and pulled away sticky fingers, but now, the sap is solid, a little flaky, and cemented to the bark of the tree. I can’t help but think about maple syrup and wonder, how cold does sap need to be to freeze?

As I feel the sap, I can’t help but feel the bark of the tree as well and its rough, mottled texture reminds me of cornflakes or similar cereals. It almost feels like I could pull these flakes off and make a bowl of “spruce flakes” but even as I feel it, I can tell the bark is firmly secured and would be quite the challenge to “flake” off.

So many questions, thoughts, and ideas pop into my mind every time I see these trees. And while I could go on for pages about all three topics, I think I’d like to these observations to answer the question posed earlier: “Why is there a ring cut into some of the trees throughout the forest?”

What Makes This Tree Different?

To start, let’s take a moment to identify the tree itself. The trees subject to this odd cut are Norway Spruces, they make up a large portion of the forest just beyond the parking lot and workshop along the trail to the North Bridge and Pikes Passage Bridge. These evergreens can grow quickly, reaching a height of 60 feet tall in a short twenty years. In its native European habitat, it can even grow to be 150 feet tall!

These trees being so far from their native habitat is part of the reason you might find a cut ring on the trunk. Nonnative trees like this are great for creating quick forests where there was once only agricultural field, but ideally, we want to restore the forest to native species like White pine, Hemlock, Black spruce, and other species. So as new native trees get planted, old Norway spruces get chopped down or have ring cut in them.

Pearson Scott ForesmanCambium (PSF), marked as public domain, more details on Wikimedia Commons

This process, called girdling, effectively kills the tree by removing the protective bark and the cambium layer. The bark protects the tree from sickness, fires, impacts and more while the cambium layer is responsible for creating new growth of the tree and passing nutrients between the roots and the canopy of the tree.

Without the protective bark or the cambium pathways for nutrients to travel, the tree will starve. The sap dripping down the trunk can no longer make it to the canopy high above. But it begs the question, “why not just cut the tree down?

Girdled to Make a Healthier Forest

If we wanted to just remove the trees, cutting them down would be best, but girdling some of the trees and leaving them purposely creates standing dead trees which provide essential forest habitat for a wide variety of species including mammals, birds, insects, and even amphibians. Research done on “Attributes of Standing Dead Trees in Forests” indicates that on average, healthy forests in the United States tend to have 11 standing live trees for every standing dead one. By girdling a few trees, we are purposefully creating habitat that better aligns with other healthy forests.

So, the next time you hike Crossroads and find a girdled tree, pause a moment and try to identify the cambium layer, the state of the sap and what animals might decide to make a home in it. These trees may look odd, but they have an important role to play in our forest habitats.

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