Category Archives: Tryon Creek
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
The plants growing at Tryon Creek State Natural Area (TCSNA) require a supply of nutrients to stay healthy and keep growing. An important part of supplying those nutrients is the decay of dead organic matter like leaves and branches. This decay process releases the chemicals in the dead leaves and branches so those nutrients can be reused by plants that are still growing.
To study this process, I collected leaves, branches or cone scales of several species of trees found at TCSNA in September 2014. I only collected fresh materials which had recently fallen to the ground. Within two days I placed these in wire mesh (screen) “envelopes” and fastened the envelopes to the ground with nails. During the first part of the study I took photographs of the envelopes on a monthly or quarterly basis, but starting in September of 2016 I switched to once-a-year monitoring. The results after one and two years have already been published in earlier Naturalist Notes.
The one-, two- and three-year end results are presented here. While I had two envelopes for each of the materials, I only selected the most photogenic envelope for inclusion in this report.
Red Alder (Alnus rubra) Leaves
Red alder is a common tree at TCSNA, and is renowned for dropping its high nitrogen leaves onto the ground while they are still green. The results from this study are seen in the photos below.
One university research project studying the decay of dead red alder leaves indicated that 93% of the nitrogen in the alder leaves was released into the soil via the decay process the first year. The same study found that 91% of the calcium and 97% of the potassium (both key nutrients) were also released during the first year of leaf decay1. This relatively rapid decay of the red alder leaves was attributed to the fact that they generally contain higher levels of nutrients than most trees, thus nourishing the decay organisms.
Western Redcedar (Thuja plicata) Branchlets
In sharp contrast to the red alder leaves, the western redcedar foliage contains lower levels of many nutrients, thus making it a somewhat less attractive food source for microorganisms. In addition, redcedar foliage and twigs contain many terpenes. Terpenes not only give the tree it’s distinctive “cedar smell,” but terpenes also have anti-fungal properties. The major terpene in western redcedar (α-thujone ) is shown below.
No wonder that the cedar is decaying a little more slowly than some of the other samples.
Bigleaf Maple (Acer macrophyllum) Leaves
With no special chemical defenses against fungi, and a fairly high nutrient content, the maple leaves are another fast decaying material.
Douglas-fir (Pseudotsuga menziesii) cone scales
These Douglas-fir cone scales were already lying on the ground at the time of collection. The cones they came from had probably been chewed apart by a squirrel looking for the nutritious seeds.
Superficially, the cone scales after three years look almost exactly like they did the day I put them in the bag. Obviously the scales are made up of a very hard material, not too much different than the wood in the main stem of the tree. Mother Nature made the cone scales very durable to protect the precious young seeds, and as a result, they are being recycled very slowly.
Again, the Douglas-fir twigs and foliage contain some terpenes similar to the terpenes found in the redcedar, and thus, they decay more slowly than the alder and maple leaves. Notwithstanding the resistance to decay, all the needles have fallen off the twigs.
The End Result
The nutrients within each of the samples used in this study will be released and then absorbed by living plants and fungus, helping the forest to grow the next generation of life. This study shows the enormous differences in the decay times of different kinds of tree litter. The softer materials, like the alder and maple leaves also have the highest nutrient content, and lowest concentration of anti-fungal chemicals. But, as the old saying goes, “All in good time!” All these nutrients will once again join living organisms, ensuring the continuation of TCSNA’s forest!
1Radwan, M. A., Constance A. Harrington and J. M. Kraft. 1984. Litterfall and nutrient returns in red alder stands in western Washington. Plant and Soil 79(3):343-351.
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.
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
At the most basic level, the universe is orderly, although sometimes that order is not immediately apparent. Albert Einstein famously remarked, “God does not play dice with the universe.” Fortunately, in the forests of Tryon Creek State Natural Area (TCSNA) we have many wonderful examples of the orderliness of the universe. For this article I will focus on the symmetry that we see in so many of the organisms in the forest.
The most common types of symmetry we can see at TCSNA are typically referred to as spherical, radial and bilateral symmetry. Another way to think about these kinds of symmetry is symmetry around a point, symmetry around a line and symmetry around a plane.
Spherical Symmetry (Symmetry around a point)
With spherical symmetry, there is one point in the middle of an object, and no matter which direction you go from that point, everything is the same. If you’ve already guessed that all the examples are spheres, you’re right! The seeds and fruits of some plants are the best examples of this at TCSNA. For example, the picture below shows the fruit of a bedstraw (a.k.a. “cleaver”) plant (Gallium spp.) The scar in the middle of the picture is where the fruit was attached to the stem.
Other forms of symmetry get a little more interesting.
Radial Symmetry (Symmetry around a line)
A second type of symmetry is radial, where there is a central axis to the object, and the parts all stick out equally in any direction from that central axis. One of the best examples can be seen in this mushroom fruiting body. Imagine the red dashed line going down the center of the stem of the mushroom. At a given distance from the ground, if you travel out at any 90° angle to that red line the mushroom structure is identical.
The picture below is of the underside of the mushroom’s cap. I’ve put in a red dot to indicate the central axis of the fruiting body. No matter which direction you look out from the center, the structure looks essentially the same. The edges of the gills that you see as lines, all point to the center of the mushroom.
Looking at the underside of the mushroom’s cap provides an additional perspective on radial symmetry.
The mushroom above is an example of the simplest kind of radial symmetry. But radial symmetry can be more complicated, and more interesting.
Spirals – A special case of radial symmetry
The mushroom pictured above is a very simple example of radial symmetry, but more complex examples can be easily found at TCSNA. The most obvious are some of our native conifers. For example, at first glance the scales on a Douglas-fir (Pseudotsuga menziesii) cone might appear to be arranged in a random pattern.
In fact, the scales on a Douglas-fir cone are arranged in a definite spiral pattern around a central stalk. The scales are actually arranged in multiple spiral patterns. To illustrate this I painted the bracts (the three-pointed papery structure attached to each cone scale) to highlight these spirals. Each spiral is a different color. The results can be seen in the movie below. Since each cone scale is actually part of three different spiral patterns, I have painted three different cones, each illustrating one of the three patterns. A different color of paint was used to mark each of the spirals. Watch first one cone and then the others to see these three different spiral patterns.
You can see in the movie that there are a set of three spirals of cone scales going in one direction around the cone axis at a very gradual angle. There is a second set of five spirals going around the cone at a steeper angle in the opposite direction. Finally, there is a third set of eight very steep spirals going about the cone in the same direction as the first set of spirals. So each scale is part of all three spirals going around the cone’s central axis.
In any given plant, the number of spirals are a part of a set of numbers known as the Fibonacci sequence of numbers. The Fibonacci numbers were described by an Italian mathematician more than 800 years ago (and Indian mathematicians had apparently described them even before that). Starting with the number 1, each subsequent number is the sum of the two previous numbers. Below is the start of the original Fibonacci sequence (the “modern” version starts with zero, which has no impact on the rest of the sequence):
1, 1, 2, 3, 5, 8, 13, 21, 34, etc, etc, ad infinitum.
In the botanical literature, it is traditionally reported that the number of spirals in any plant are always two consecutive numbers of the Fibonacci sequence. With one exception. The pineapple fruit is almost always described as having three spirals. I present here the possibility that the Douglas-fir cone, like the pineapple, is composed of three spirals, not the traditionally recognized two. But, whether it’s two spirals or three, it represents an example of order in nature.
Bilateral Symmetry (Symmetry around a plane)
Finally, there is bilateral symmetry, which is symmetry with respect to a plane (think of a sheet of glass). The structure is identical on both sides of the plane. The butterfly below is a beautiful example of bilateral symmetry. Think of an imaginary sheet of glass running vertically through the butterfly’s body. Each side of the body is an identical mirror image of the other side. The easiest feature to see in the photo below are the patterns on the wings.
Plants often exhibit bilateral symmetry, as exemplified by the bigleaf maple (Acer macrophyllum) fruit shown below. In fact there are two different planes of symmetry. The first one is centered around the red line drawn on the picture. The second plane of symmetry is represented by the paper on which this picture could be printed. The front and back sides of the seed are identical.
But wait… Not everything in the forest is symmetrical!
My favorite example of a non-symmetric organism in the forest is the banana slug (Ariolimax columbianus). Below are two pictures of the same slug. One picture is of the right side of the forward part of its body, and the other is of the left side of the forward part of its body. As you can see, the slug only has one breathing hole, and it is on the right side of its body. Thus, the slug does not display symmetry in this regard, it is asymmetrical. Every slug has its breathing hole on the right hand side of the body.
But that’s not the only way a slug is asymmetrical! Look at the coloration on the body of the slug pictured below. A black spot on one side of the slug is not matched with an equal sized, or shaped black spot on the other side of its body.
Symmetry is often useful, such as birds having one wing on each side of its body. Imagine a bird trying to fly with both wings on the same side of its body. But In truth, while nature has intended many things to be symmetrical, oftentimes the symmetry is not perfect. These imperfections may result from mutations during development, or accidents. So what you ask? Scientists have discovered that some animals, like female peahens and barn swallows, prefer males with symmetrical tails. To the birds, symmetry could be proof of a potential mate’s normalcy, which is often the safe choice.
The symmetrical patterns that we see in much of the flora and fauna of TCSNA provide some reassurance in the orderliness of the universe. It suggests that perhaps Einstein was correct!