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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.




Fungus Among Us

Fungi in the Forest

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester


The fungi (singular = fungus) at Tryon Creek State Natural Area (TCSNA) are endlessly interesting. They’re more than just the cute mushrooms along the side of the trail. They take on many forms, and have more diverse lifestyles and habitat preferences than we might imagine.


What do fungi look like?

When you say “fungus” most people think of either mushrooms, or that fuzzy stuff on the tomato you left on the counter too long.  In truth, they can look like almost anything.

A hypha (plural = hyphae) is a single living “thread” of a fungus. Hyphae are the building blocks of every part of the fungus. Even mushrooms, the fruiting body of some fungi, are just a tightly packed bunch of hyphae. The fungus pictured below grew underneath the loose bark of a dead western redcedar (Thuja plicata) tree on the Big Fir Trail. The fuzzy white strands surrounding the solid central tan fungal mass are a good example of fungal hyphae.



Hyphae of this fungus are reaching out along the edges

 Some fungi do something really different. The honey fungus (Armillaria mellea), for example, sometimes uses a huge number of hyphae to create a structure called a “rhizomorph”. Rhizomorph roughly means “root-like thing.” These rhizomorphs are essentially hollow tubes made up of many, many hyphae. They are typically 3 or 4 mm wide (about 1/8 of an inch). Rhizomorphs are created by the fungus to move water and nutrients from one place to another. It has been suggested that when the fungus starts running out of nutrients in one place, it uses the rhizomorph to “explore” for another good location, and then transports some nutrients to that location to jump start the next fungal infection. The rhizomorphs of the honey fungus are black and about the same dimensions as a shoelace. In fact, foresters refer to this species as “the shoelace fungus.” The rhizomorph frequently grows between the bark and the woody tissue of the tree. The photo below shows a log lying alongside Old Main Trail. Several rhizomorphs are clustered side-by-side to form the big black splotch in the middle. This rhizomorph became visible when the bark fell off the log.


Old black rhizomorphs that grew under the bark of a tree


What else might fungi look like?

One form of fungus that is common to the bigleaf maple (Acer macrophyllum), is powdery mildew that grows on the surface of the leaf. Mostly it just looks like a light coating of white fuzz or dust, but it is a fungus. Sometimes you may see black dots which are the spore-producing bodies of this fungus.


Powdery mildew on a bigleaf maple leaf.


What do fungi like to eat?

You might think that since fungi are mostly just “rotting stuff” that they would eat anything. However, certain fungi have definite food preferences. Take for example wood decaying fungi. In medium or larger woody plants, there are two distinct kinds of wood. In the cross-section of a Douglas-fir (Pseudotsuga menziesii) below you can see two different colors of wood. The peach-colored wood in the middle is the heartwood, while the pale wood around the edge is the sapwood.


Cross section of Douglas-fir tree trunk


For fungi, the heartwood and the sapwood are two different types of food.


The bad news: It is loaded with chemicals (generically called “extractives”) which inhibit the growth of fungi. It contains very little easily digestible nutrients like stored starch.

The good news: There are no living cells to “fight back” against a fungal invasion.



The bad news: There are lots of living cells which sometimes fight back against the fungi.

The good news: There are lots of easily digestible stored foods like starch and sugars.


As you might suspect, some fungi have evolved to favor the heartwood, and some fungi have evolved to favor the sapwood. One manifestation of these preferences was found on the end of a log at TCSNA on the ground near the Nature Center. The fungal fruiting bodies indicated by the red arrows are from a species growing in the sapwood. The fungal fruiting bodies indicated by the white arrows are of a species growing in the heartwood. The third fungus, indicated by the yellow arrow, is also growing in the sapwood. I have seen other examples of this kind of distribution, but this was the most dramatic. Please note that the lower part of the log is hidden by the dead leaves on the ground.


Log showing different fungi growing in heartwood and sapwood areas.


What parts of the wood are the fungi eating?

Not only do different fungi attack different parts of the tree, they also eat different chemicals in the wood. Wood is made up of two main chemicals. The first is cellulose, and the second is lignin. Cellulose is a simple molecule made up of a long chain of glucose (a type of sugar) molecules, and only glucose molecules. Each glucose molecule is bonded to the next glucose in the same way. Lignin, in comparison, is a very complex molecule. It is made up of a variety of molecules, which are linked together into a network, not a nice straight chain. In addition, the bonds between the molecules which make up lignin are extremely variable.

Fungi use enzymes to break down large molecules. Digestive enzymes usually have one very specific bond that they break. The bottom line is that cellulose is easier to digest than lignin. The diagrams below convey the idea of lignin being complex compared to simplicity of cellulose. The colored shapes are the component molecules of cellulose and lignin, and the black lines (or chains, or spirals) represent the diversity of bonds between those molecules.

















In the real world, most wood appears to be light brown. Cellulose is pure white. Lignin is brown. So if a fungus eats all the lignin, the residue looks white. (Perversely, these fungi are called “white rot”, although the part of the wood they are eating is brown. Oh well!) My experience is that examples of white rot are less common than examples of brown rot. Pictured below is an example of white rot from a log near the Red Fox Trail.


Interior of this log was attacked by white rot fungi, leaving pure cellulose.


The fibrous cellulose left behind by the fungus is chemically identical to cotton fibers. Just think, your next tee shirt could be made out of a tree!


Close up of cellulose fibers remaining after attack by white rot fungi.


The brown rot fungi that only eat cellulose, leave behind the lignin. This is quite common. A stump with the cellulose eaten out of it is pictured below.


Stump which was attacked by brown rot fungi which digested all the cellulose.


After the wood is attacked by brown rot fungi, it tends to break into cubes. This leads to another name for this type of fungi, “brown cubical rot.” The lignin is not fibrous at all. This is seen in the picture below.


Wood residue after attack by brown cubical rot


White rot, brown rot, heart rot, powdery mildew and more, the fungi of TCSNA are a diverse and interesting bunch. They play many important roles in our forest’s ecosystem. While their small size frequently makes them hard to find, keep your eyes peeled! The rains of fall have already started to bring out their fruiting bodies in all their glory.

Discover more about our Fantastic Fungi here!


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