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A nurse log on Vancouver Island. Photo by Larissa Sayer. View photo slideshow for this story.

A nurse log on Vancouver Island. Photo by Larissa Sayer. View photo slideshow for this story.


Lessons From A Nurse Log

Sarah Waller

All week long, we are bringing you stories about Pacific Northwest trees and the role they play in our region and in our lives.

If you walk through a forest in the Pacific Northwest, you may see a row of trees growing in a perfectly straight line. They mark the place where an old tree once fell. In the next part of our series, "More Than A Tree," KUOW's Sarah Waller explores the science and symbolism of the nurse log.


I met Larry Daloz at a leadership conference on Whidbey Island. He was presenting to a roomful of professionals. Larry is an author and a naturalist. He walked in carrying a rotten log covered with moss and fungus. It smelled like wet forest.

He set it down in the center of the room. And then he went on to talk about the importance of leaving your legacy in the community. I kept wondering: What did this rotting piece of wood have to do with the ideals of legacy? So, I asked him. Larry told me that to understand that, I better understand a few things about the log first. So, he took me out to the South Whidbey State Forest.

Daloz: "Watch your step going across this little muddy area here."

And then I see why he brought me here.

Daloz: "Here's the nurse log. Look at this puppy."

It's like the log he brought to the meeting, only super sized.

Daloz: "You could not climb over this log. It's at my head level — that's six feet up. It is a giant log, and it's rotting.

It used to be a Douglas fir tree. It lived to be about 600 years old. And then, about 30 years ago, it toppled across the trail. Now it's thick with moss. The bark is falling off. Ferns and huckleberry bushes sprout from the top. This type of fallen tree is called a nurse log.

Daloz: "Because the log itself serves as a nursery for all kinds of new growth to come up."

Larry saw a nurse log for the first time 15 years ago. It stopped him in his tracks.

Daloz: "There's something about it that just really, that just captures my imagination. I love what it seems to mean for, I think, for our lives."

So he started reading every book and article about nurse logs he could get his hands on.

Daloz: "Learning about the nurse log really scrambled my eggs about the line between life and death. It's not as clear as we sometimes think."

Larry points to the big log in front of us.

Daloz: "There's more life in this log long after it has begun to rot than there ever was when it was actually a standing tree."

Because, when a tree is standing —

Daloz: " — about 5 percent only of the tree is living tissue."

Things like leaves, buds, the tips of roots. And a thin layer of tissue under the bark, called the cambium. All the rest — about 95 percent of your typical tree — is literally dead wood. But, then it falls. And a transformation begins.

The tree life fades, but the log takes on new life. Insects and fungi move in. Tree seedlings take root. And that's when it becomes a nurse log.

Daloz: "If you were to weigh all of the living cells that are inside and permeate through the nurse log, it would be about five times as much material, living material, after it is on the ground as it was when it was a standing tree."

And that fact that these hunks of dead wood act like cradles for new life is critical for Northwest forests.

Daloz: "And very often you'll be walking through an old growth forest and you'll see these hemlock trees that look as though they're standing on their roots with huge spaces between them. Well, the reason it gets that way is that they grew up on a nurse log, which is since rotted away and left these strange standing trees looking like frozen octopuses in the middle of the forest."

Nurse logs also act like giant sponges. They store the moisture throughout the year and release it during times of summer drought. This allows Washington forests to preserve their signature green lushness. And nurse logs have symbolic importance too.

Daloz: "One thing I think about when I look at a nurse log like this is that after it falls, the soil it leaves behind is much richer than what was there before, and maybe that would be a great way to live. May our legacy that we leave behind be richer than what we found when we came."

This nurse log will take about 600 years to fully decompose back into soil. So, if you happen to visit this spot on Whidbey Island in the year 2600, you would probably see its legacy: a new generation of hemlock trees growing in a straight line where this log once lay.

I'm Sarah Waller for KUOW.

© Copyright 2012, KUOW