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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.

Photo 1

Top of alder broken off near Red Fox Bridge.


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.

Photo 2

View of the sky where the alder fell down.


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!

Photo 3

Red alder seeds on the trail (green Douglas-fir needle at bottom provides perspective).


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).

Photo 4

Western redcedar stem lying across the trail (note pen for scale).


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).

Photo 5

Dead top of the fallen western redcedar tree.


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.

Photo 6

Fork-topped Douglas-fir on the ground after a heavy snowstorm.


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.

Photo 7

Broken, semi-rotten top end of one of the major stems on a Douglas-fir.


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.

Photo 8

Pencil stuck in stub of tree trunk.


Photo 9

This is how far I could stick the pencil in.


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.

Photo 10

Tracks left by bark beetles eating the soft tissues of the branches.


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.

Photo 11

Heavily woodpecker-ed 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.

Photo 12

Yellow patches of pollen (?) on fresh snow near Beaver Bridge.


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.




Master Recycler

Mother Nature: Master Recycler

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester


Recycling has become a “big deal” for humans in the years since I was born! As a kid, I remember burning newspapers in the burn-barrel by our garden, and throwing a massive number of tin cans in the garbage which doubtless wound up in some landfill. Now, the Oregon Department of Environmental Quality (DEQ) proudly reports that in 2013, Oregonians recycled 53.9% of our post-consumer waste. Nice try, but we don’t even come close to Mother Nature’s record of recycling: 100%!

Here at Tryon Creek State Natural Area (TCSNA) the forest constantly recycles biomass like leaves, logs and dead animals. Sometimes it’s fast, and sometimes it’s slow, but it’s always thorough!

We need look no further than some of the TCSNA’s old logs and stumps to see that sometimes recycling takes quite a while. This rotting log is approximately 18” in diameter. It is on the side of Old Main Trail and hasn’t changed much in the last 5 years, and I don’t expect it to completely disintegrate any time soon. In fact, research foresters report that fallen Douglas-fir (Pseudotsuga menziesii) logs sometimes take almost 200 years to completely decay!


This might even be here for over another 100 years!


But other stuff “recycles” faster, doesn’t it?

Absolutely! In order to see how fast things are recycling (“decaying”) at TCSNA, I set up a small study. Scientists who want to study recycling in the forest often use things called “litter bags.” (The term “litter” here refers to the fallen leaves, twigs and branches on the ground, not to candy wrappers and used Kleenex!) I collected the plant material for this study off the ground, so this material was ready to start decaying.

I cut square pieces of window screen to make my bags. I placed the plant material on half of each piece of screen, and then folded the other half over the top, and stapled it shut. I fastened each bag to the ground using four big nails, one in each corner. I set up the bags in an area of TCSNA where they wouldn’t be disturbed. I put out some bags on September 11 and others on September 13, 2014.

In each bag, I put one of five things; Alder (Alnus rubra) leaves, bigleaf maple (Acer macrophyllum) leaves, western redcedar (Thuja plicata) twigs with their green scaly leaves, Douglas-fir twigs with needles, and finally, the scales from a Douglas-fir cone. I had two bags of each type of material. Then I fastened the bags to the ground.


So what happened?

This is what it looked like on September 13, 2014, after the full study was installed. You can see some of the green leaves inside the bags.


Litter bags fastened down on the forest floor.

I took pictures of every bag each month. When I took pictures I brushed off the top of the bag, loosened two of the nails holding it to the ground, and slipped a piece of white plastic underneath the bag to provide contrast to the material inside the bag. I refastened the bags and replaced the litter following each photo. Below are some highlights.

By October 3, 2014 some natural forest litter had fallen on the bags. This is totally realistic. There were times when the litter bags were almost completely covered with natural litter from the trees.


The litter bags after 20 days in the forest.

Having the litter inside bags did create a certain amount of unrealism. This point was made dramatically during my March 2015 visit to the litter bags, when the little critter pictured below was crawling over them. To the extent that snails might accelerate litter decomposition, my study was only an approximation of reality.


This snail will never get at the litter in my litter bags. Sorry, little guy!


So let’s see the decay process!

The decay rates for the samples in my litter bags varied a lot between species, and sometimes between particular leaves of the same species.


Red Alder


Alder leaves on Sept. 11, 2014 “Day 0”


Alder leaves on November 26, 2014













Alder leaves on March 28, 2015


Alder leaves on Sept 27, 2015












The alder leaves decayed dramatically over the course of a year. After 79 days, the leaves had lost their color, but had only just started to disintegrate. By the end of March, the leaf in the upper half of the photos was pretty much reduced to the mid-rib (the tough “vein” going from the base of the leaf right through to the tip) and the lateral veins. In contrast, the leaf in the lower right hand corner still had a lot of the leaf blade left.


Bigleaf Maple


Maple leaves on Sept. 11, 2014 “Day 0”


Maple leaves on November 26, 2014















Maple leaves on March 28, 2015


Maple leaves on Sept 27, 2015












Once again, the maple leaves were significantly decayed after the first year, but the petiole (the stalk that attaches the leaf to the branch) being more “woody” than the leaf blade is still largely intact.


Western Redcedar


Western redcedar on Sept 11, 2014 “Day 0”


Western redcedar on November 26, 2014















Western redcedar on March 28, 2015


Western redcedar on Sept 27, 2015













Western redcedar is loaded with hydrocarbon molecules that impart decay resistance. The most amazing thing was that in November 2015, after more than two months on the ground, most of the redcedar branch was still green! (Confession time: The other redcedar branch had turned completely brown at this point.) After over a year on the forest floor, this branch, and its needles, was still largely intact.

Douglas-fir twig


Douglas-fir on Sept 13, 2014 “Day 0”


Douglas-fir on November 26, 2014















Douglas-fir on March 28, 2015


Douglas-fir on Sept 27, 2015













Unlike the alder and maple samples, this bag includes the woody twig in addition to the foliage. The Douglas-fir twig rapidly shed all its needles, producing an un-photogenic combination of a bare twig, and clumps of dead needles. The slight movement of the bags in preparation for taking photos is what caused the needles to gather in clumps. The needles, though brown and scattered, are individually maintaining their structural integrity. As with the western redcedar discussed earlier, the presence of hydrocarbon molecules in the needles and stem are helping resist decay.


Douglas-fir cone scales

The Douglas-fir cone scales are tough and woody. To tell the story of their decay in the first year, we only need two photos. In the 12+ months in the litter bag, there was no perceptible change in the Douglas-fir cone scales, except they are now slightly darker! Again, shifting the bag for photos results in shifting the scales around within the bag.


Douglas-fir cone scales, Sept 13, 2014 “Day 0”


Douglas-fir cone scales, Sept 27, 2015











The Cycle: Life > Death > Life

As organic matter decays, important chemicals like nitrogen and phosphorus are slowly released to soil for growing plants. The partially decayed organic matter in the soil dramatically increases its moisture holding capacity, and water infiltration rates, among other things. Better than most of us, Mother Nature knows that the rotting leaves and stems of today are the key to the towering trees of tomorrow! Without recycling, there would be no forest as we know it.




What’s that “yucky stuff?”

The “Yucky Stuff” in the Creek

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester


People come to Tryon Creek State Natural Area (TCSNA) to enjoy nature’s beauty. They want to enjoy a natural and pristine environment, largely unspoiled by humankind. Our free-flowing Tryon Creek is an object of particular attraction.

As beautiful as the creek can be, some visitors are alarmed when they see “pollution” (often referred to as “yucky stuff”) in the creek. The truth of the matter is, that what might look like “pollution” in the creek is oftentimes the result of purely natural processes, not pollution at all.

The two most common kinds of “yucky stuff” in the creek are white foam floating on the surface, and orange slime in the water. Once you understand these two kinds of “yucky stuff,” you can relax.


So what’s with the white foam?

Sometimes you can see large clumps of floating foam accumulate on the upstream side of logs or other barriers in the creek. A typical mass of foam, pictured below, spotted recently just upstream from Obie’s Bridge:


Foam floating in Tryon Creek

You might think it’s soapsuds that leaked into the creek, but it’s probably not human-made at all. What really happened is a longer, but more interesting story.

The edge of the creek is lined with all kinds of trees, especially red alder (Alnus rubra). Alders being alders, every fall dump huge numbers of leaves into the creek, as you can see in the photo below.


Fresh alder leaves floating in the creek and lying on the bank

And leaves being leaves, they start to decay, oftentimes in the stream itself. The photo below shows a large clump of mostly alder leaves (now brown) that have sunk to the bottom of Tryon Creek. Numerous microorganisms are decomposing these leaves. Note the tiny clumps of white foam floating on the surface above these leaves.


Clump of old alder leaves on the bottom of the creek

So the leaves decay. Now what?

As microorganisms decay the leaves, DOC (dissolved organic carbon) is released into the water. DOC is a totally natural mesh-mash of different chemicals. One of the DOC chemicals is palmitic acid, which is shown below.


Chemical structure of palmitic acid

Palmitic acid is found in every red alder leaf. It is a major part of each cell’s membrane. Palmitic acid, or closely related chemicals, are found in every plant. Below is the chemical structure of a typical soap molecule manufactured by humans.


Chemical structure of soap

The resemblance is unmistakable. There are two more carbons in the soap, but the major difference is highlighted in red in the diagrams. It is easy to see how the palmitic acid might act a lot like soap.


Why do we get foam?

Normally, the water molecules at the surface strongly attract each other, and form what is basically a weak shield on top of the water. We call this shield “surface tension.” Small insects called water striders can be seen walking on this surface tension on top of the creek in the summer.

To see a demonstration of surface tension, please play the following video.


Click on the Water strider to play the video!


The DOC, just like soap, interferes with the natural bonding between water molecules in the surface tension layer. The end result of the soap or palmitic acid is that when air gets into the surface layers of the water, it isn’t squeezed out by the natural mutual attraction of the water molecules. Rather, the air enters the water and with a bit of agitation creates bubbly foam.

To demonstrate natural foam-making, I used a jar of Douglas-fir (Pseudotsuga menziesii) cones that had been sitting on my home office desk soaking in water for about two months. [Note: If you happen to see my wife at TCSNA, please casually mention that you also have a jar of Douglas-fir cones soaking on your home office desk. It will help me a lot!] I used this jar to demonstrate that you can create foam just from decaying vegetation. All you need is some agitation, like what you might get from “rapids” in the creek. Photos of this jar at various stages appear below. Note how much foam is floating on top of the water.


Soaked cones in jar before shaking – no foam.


Cone jar right after shaking – lots of floating foam.


Cone jar 90 minutes after shaking – still some foam.

The foam persisted for a long time after the shaking. If this foam were produced in the creek, in 90 minutes it could travel a long way downstream.


So we’ve got white foam in the creek, what else?

The second type of “yucky stuff” we have in the creek is orange slime! This can be found in a couple of places at certain times of the year. I’ve seen some in the vicinity of Obie’s and Beaver Bridges. How this comes about is one of the most interesting and unexpected nature stories at TCSNA. The photo below shows a pool of orange slime in the creek.


Some “orange slime” in Tryon Creek.

Most of us have been told at one time or another that there are two types of organisms in the world. First there are those that use sunlight, water and carbon dioxide to produce sugar to provide energy for themselves. This is what salmonberries (Rubus spectabilis) and Douglas-fir trees do. They are called “autotrophs” from the Greek meaning “self- nourishing.” Second, there are organisms which eat and “burn” the carbon compounds produced by autotrophs to produce energy for themselves. These carbon compounds are as diverse as sugar and wood. This is how both banana slugs (Ariolimax columbianus) and people (Homo sapiens) survive. These organisms are called “heterotrophs,” from the Greek “other nourishing.”

Following this explanation, we see that the energy of the sun is the basis for all organisms. So far, so good, and if you are in 2nd grade, this is a decent way to start understanding life. However, the organism that makes the orange slime doesn’t fit into either of those categories. It’s weird!


I love weird stuff! Tell me more!

The weird organism is a special type of bacteria called “iron bacteria”. (I’ll skip lots of complex chemistry here! “You’re welcome!”) You and I eat carbohydrates like corn, donuts and potatoes, and oxidize it to get energy. In the process we give off carbon dioxide (each time we exhale) and water (through sweat, breath and urine).

Iron bacteria don’t do that. These bacteria “eat” a special iron compound (ferrous iron, if you must know). Ferrous iron is found underground where there is a deficiency of oxygen. As water carries it up towards the surface of the ground it encounters both more oxygen, and the iron bacteria. The iron bacteria oxidizes (“eats” to put it crudely) the ferrous iron, and “poops” regular old rust (ferric iron, for you geeks). These iron bacteria are classified as “chemoautotrophs” meaning roughly, “they feed themselves with chemicals.” That’s right, the orange slime you see in the creek is essentially rust excreted by these special bacteria. In eating this special iron, the bacteria get the energy they need to live. The photo below shows the ferric iron seeping out of the soil into the creek.


Iron oxide (“orange slime”) emerging from soil (at white arrow) and oozing into Tryon Creek.

Given that TCSNA is just a few miles from an old iron mine, it’s not surprising that TCSNA’s soil contains the high levels of iron needed to support this kind of bacteria.

Unlike what you may have been led to believe many years ago, these bacteria represent a group of organisms which don’t rely on energy from the sun to stay alive. If the sun ever goes away, no more plants, no more bugs, no more birds, and no more people. Then the iron bacteria will have TCSNA all to themselves. It probably won’t be a very exciting place, but there will still be life here!

The next time you see some “yucky stuff” in the creek, pause for second before calling it pollution. You might just be seeing the end result of some very interesting natural processes. The floating white foam and orange slime are just as much a natural part of TCSNA as your favorite birds and flowers. They are another reminder that nature is endlessly fascinating.









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