Author Archives: tryoncreeknaturalist

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.

 

 

Nature’s Patterns

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.

photo-1

Bedstraw seed with spherical symmetry

 

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.

photo-2

A mushroom with radial symmetry

 

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.

photo-3

Underside of a mushroom cap, showing 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.

photo-4

Douglas-fir cone

 

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.

photo-5

Red admiral butterfly (Vanessa atalanta) near the Middle Creek Trail

 

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.

photo-6

Bigleaf maple seed with two planes of bilateral symmetry

 

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.

photo-7

Photo left: right side of slug’s body (arrow points to breathing hole). Photo right: left side of slug’s body (no breathing hole)

 

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.

photo-8

Banana slug showing asymmetrical coloration patterns

 

Why symmetry?

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!

Recycling the Forest: Year 2

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester

 

Mother Nature is the world’s first, largest and best recycler!  Each year in Tryon Creek State Natural Area (TCSNA), tons of organic matter like trees, dead animals and coyote feces are recycled.  This recycled material is used by the forest to grow new trees, birds and mice, to name just a few.  If it weren’t for recycling, the surface of the earth would be covered with unimaginable amounts of dead organic matter.  In addition, it would be tough for any new organisms to grow because so many materials vital to life would be locked up in the litter.

Two years ago, I started a small study at TCSNA to determine just how fast the recycling process is in our forest.  The first year’s results were published in a Naturalist Note last fall.  To access this previous note, use this link, and then scroll to the bottom.  This second Naturalist Note takes a look at the results after two years.

 

How it works…

As indicated in the previous Naturalist Note, samples of five different kinds of fresh organic matter were collected from the ground in TCSNA in the fall of 2014.  Collecting them from the ground insured that they were naturally ready to start being recycled.  The samples included a) red alder (Alnus rubra) leaves, b)  bigleaf maple (Acer macrophyllum) leaves, c)  western redcedar (Thuja plicata) branchlets, d) Douglas-fir (Pseudotsuga menziesii) branchlets, and e) scales from a Douglas-fir cone that had been chewed apart by a squirrel.  Two samples of each thing were collected, for a total of 10 samples.

Each sample was placed inside a flat “bag” made of standard plastic window screen material.  The bags were then taken into the forest, placed down flat on the forest floor, and fastened down by inserting a nail through the corner of each screen down into the ground.

From September 2015 through September 2016, pictures were taken on a quarterly basis.  The results after two full years can be seen in the photos below.  The first photo shows the array of litter bags before I disturbed them to take the photos.  The silvery-gray bits seen in the photo are the exposed part of the screen bags.  As you can see, there were also some plants growing up through the litter bag array.

 

photo-1

Undisturbed array of litter decay bags on September 21, 2016.

 

They’ve really changed!

The rate of decay of materials from the different species varies dramatically.  Specific samples are shown below.  The first two sets of pictures show the two different red alder leaf bags.  I’ve included both sets of red alder bags to show that there is a certain amount of bag-to-bag variation in the rate of decay.  For the remainder of the species in the study, I’ve included only one of the two bags.  You may observe that due to my picking up these bags periodically for photos, the position of some of the materials in the bags has shifted a bit.

 

photo-2-and-3-combined

Red alder leaf bag #1, left: September 11, 2014, right: September 21, 2016

 

 

photo-4-and-5

Red alder leaf bag #2, left: September 11, 2014, right: September 21, 2016

 

While most of the leaf blades are substantially degraded, some of the veins are still intact.  This is typical of many different leaf decay studies.

The following photos are of one of the bags containing bigleaf maple leaves.  Again, you can see that the leaf blades themselves are pretty well decayed, but some of the veins, and petiole (the “stem” that connects the leaf blade to the branch) are still identifiable.

 

photo-6-and-7

Bigleaf maple bag #1, left: September 11, 2014, right: September 21, 2016

 

…Or maybe not so much!

The remaining samples are all from conifers, which retain their foliage for more than a single season.  If you could feel their foliage, you could tell it was definitely tougher.  This becomes evident in the photos below.

The western redcedar foliage has not only not decayed very much, but also, many of the leaf scales are still attached to the branchlets.  I’m impressed!

 

photo-8-and-9

Western redcedar bag #2, left: September 11, 2014, right: September 21, 2016

 

Most of the Douglas-fir needles in the bag shown below have fallen off the twigs, but they still appear to be largely intact.  Detailed scientific studies suggest that while there has probably been some substantial decay inside the needles, the outer tough surface of the needle has been somewhat resistant.  One unfortunate thing with the Douglas-fir branches is that once the needles have fallen off the twig, they can easily slip through the mesh screen when they are jostled very much.  I have no doubt that some of the needles that were originally on the twig have fallen out of the bag.

 

photo-10-and-11

Douglas-fir branch bag #2, left: September 11, 2014, right: September 21, 2016

 

The final set of photos below show the tough cone scales of the Douglas-fir which appear to be only minimally changed over the course of two years on the ground.  This is not surprising, given that the cones are made tough to protect the seeds of the tree.  Also, the cones tend to have high resin content, and thus resist decay.

 

photo-12-and-13

Douglas-fir cone scales bag #2, left: September 11, 2014, right: September 21, 2016

 

Litter as fertilizer

Litter contains vital nutrients that help trees grow.  One of the advantages of relatively slow litter decay is that the litter then acts as a “slow-release fertilizer” a method of ensuring that the living plants will have ample opportunity to absorb it to assist with their growth.

But long before the nutrients trapped in the litter help the next generation of trees and shrubs grow, those nutrients help the fungus and bacteria that decay leaves grow.  And just like you, the microorganisms are more attracted to a lavish banquet than to a bowl of thin soup.  The more nutritious the litter, the faster it decays1.  For example, red alder leaves have 4 times the nitrogen content of either western redcedar or Douglas-fir foliage.  Bigleaf maple litter has more than 3 times as much phosphorus as either western redcedar or Douglas-fir.  Both red alder and bigleaf maple have more than 10 times the amount of potassium as Douglas-fir litter.  Viewed from the perspective of nutrient contents, it’s no surprise that the red alder and bigleaf maple foliage decays faster.

It was found in the mid-1970s that applying urea fertilizer containing 200 lbs of nitrogen per acre to Oregon’s Douglas-fir forests, significantly increased their growth rate.  As noted above, red alder leaves, due to the nitrogen-fixing nodules on the alder roots, contain relatively high levels of nitrogen.  The photo below shows the amounts of urea fertilizer (the typical nitrogen fertilizer for forests) and alder leaves that would be needed to provide 200 lbs/acre of nitrogen.  So the decaying leaves, especially the alder leaves, are acting as a slow release fertilizer.
 

photo-14

The box of dried alder leaves contains as much nitrogen as the small vial of white urea.

 

The dead plant parts like tree trunks, branches, leaves and even the unseen roots, are important parts of the whole cycle of life at TCSNA, as well as in other forests.  In their role as nutrient recyclers, the fungus and bacteria that decay the forest litter play a vital role in helping maintain a healthy and vigorous forest.  Recycling is an important example of how different parts of the forest work together to create the TCSNA we love so much.

___________

1Valachovic, Y. S., B. A. Caldwell, K. Cromack Jr., and R. P. Griffiths.  2004.  Leaf litter chemistry controls on decomposition of Pacific Northwest trees and woody shrubs.  Can. J. For. Res.  34:2131-2146.

 

 

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