Our Dynamic Forest
By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester
This year January brought us an unusually wet, heavy snow. In my Lake Oswego backyard, it amounted to just over 7-1/2 inches of the white stuff. The snow at Tryon Creek State Natural Area (TCSNA) was roughly similar. As with so many other unusual events, it was a great opportunity to learn more about our forest.
The wet, heavy snow brought many changes. Some that we humans, entranced with the visual wonder that is our forest, tend to regard as tragic. But Nature may have a different view. Let’s take a look at some of the things that happened.
Look out below!
All kinds of trees fell down. As shown in the photo below, the top snapped off from this red alder (Alnus rubra) growing near Red Fox Bridge. You can see the top lying on the ground. For the alder, this is a horrific setback, if not death.
However, the plants growing on the ground under this alder may have a different perspective. I stood right over the alder trunk lying on the ground, pointed my camera upwards and took this picture of a significant hole in the canopy.
Do you suppose the plants growing on the ground are looking up and thinking, “Oh what a tragedy. Now we’re going to be growing in full, life-giving sunlight, and we won’t have competition from the alder.” No matter what kind of tragedy it was for the tree that fell down, many of the neighboring plants will be celebrating because of the extra sunlight they will be receiving.
And if the existing plants already on the ground aren’t able to jump in and take advantage of the newly sunny spot, rest assured that some new plants will. The photo below shows numerous red alder seeds (two are marked with red arrows) on the Middle Creek Trail the very same day I photographed the broken alder. Finding these tiny seeds in the forested area would be very difficult, but have no doubt, they are there!
Death Cleanses the Forest
Perhaps you mourn the loss of so many good trees. In at least some cases, your tears are wasted. A storm like the one we had can be viewed in part as Nature cleaning up the forest. For example, as part of a human cleanup effort, I spent some time cutting through the trunk of a western redcedar (Thuja plicata) that was lying across the Cedar Trail so the trail would become passable (see photo below).
It was sad because it was a young tree, with potential to become one of the esteemed elders of the forest. Or so I thought. As I dragged some of the branches off the trail, I noticed the top of this tree (pictured below).
The top four to five feet of this tree had already been dead for some time. So the real story was that this tree was already having problems of one kind or another, and the storm just ended its struggle. Since it already had a dead top, its long term potential was not as great as I originally thought.
In another case, a very tall (about 115 foot) Douglas-fir (Pseudotsuga menziesii) fell down across the Old Main Trail. This is another tree that I cleared off the trail (Note: The clean-up work I did after the storm proved very educational. You might want to give it a try!) The top was forked due to some damage many years ago, as indicated in the picture below.
But this is another example of a tree that was already in trouble. The smaller branch on the right side of the picture shown above had been damaged many years before this year’s storm, as you can see below.
I sawed off the top 12” of this stub, and inserted a pencil into the soft rotten area in the center of the stem. The results are shown below.
I could easily stick the pencil a couple inches into the rotten wood. I cut 2 more feet off the end of this stub, and was still able to stick the pencil about ½” into the rotten center of the branch. Once the fungus gains this much of a foothold in a tree, it’s only a matter of time before it seriously weakens the tree.
So once again, the storm felled a tree that was already in trouble.
Dead Trees Can be Useful
And if you mourn for the dying trees, rest assured that not all of the forest inhabitants share your grief. Bark beetles lay eggs under the bark, and their larvae start burrowing through and eating the soft nutritious tissues that are right under the bark. Of the hundreds of species of bark beetles, at least some attack after the tree is dead. These beetles leave the kind of tracks like those you can see after the bark has been removed from this branch collected at TCSNA.
And of course, once insects get into a tree, can woodpeckers be far behind? The photo below shows a heavily “wood-peckered” long-dead tree along Old Main Trail.
And Some Weird Stuff…
The snow also brought at least one unique observational opportunity! Down near the creek in one area, I noticed that the snow had patches of yellow color. (No, it’s not THAT!) There were no animal tracks in this area, so I seriously doubt the yellow patches were from dogs or coyotes. According to reports on the internet, yellow snow in this context is frequently the result of pollen getting mixed in with the snow. Sadly, I got a picture, but never collected a snow sample for microscopic examination. The storm was roughly at the time that some hazel (Corylus spp.) would be shedding its pollen, but I have no proof that’s what it is.
Assuming this is pollen, I have no doubt that pollen is shed like this on the ground every year. However, it takes a snow covered forest floor before we will ever notice it.
Our Ever Changing Forest
Our forest is an ever changing ecosystem. If we could see this forest in 400 years, much of it would look unfamiliar. Most often the change is very slow, but a catastrophic event like a dramatic storm puts the changes in a time context we humans can relate to. Enjoy our forest today, because when you come back tomorrow, it will be different.