By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
Following my recent Naturalist Note on water I was persuaded to write a follow-up note, and this is it!
Water is a key to life, for both plants and animals. When you think of water at Tryon Creek State Natural Area (TCSNA), you naturally think of the creek. But that’s a long way from the whole story. In a Naturalist Note1 published earlier this year, I included the following image of how much water was in the top 12” of soil at TCSNA in late April based on 22 soil samples.
Just as a reminder, I need to stress that this is only in the top 12” of soil. In much of the park, water available to the plants might be located as deep as 2.5 feet beneath the surface. At approximately 2.5 feet beneath the surface is a layer of clay which is relatively impermeable to plant roots (more on this in my next Naturalist Note.)
During the course of this summer, there was not much rainfall, as illustrated in the graph below, which is based upon rainfall at two local stations, one at the Lake Oswego City Hall, and the other at the Westlake Fire Station.
Rainfall April 23 to Aug 23, 2018
As documented in a recent Naturalist Note, light rainfalls such as the majority of those illustrated in this graph, may primarily end up in the crowns of trees and shrubs, and never even make it to the forest floor.
On August 22 and 23, 2018 I collected soil samples from approximately the same locations where I sampled the soil in April. I again took samples from only the top 12 inches. The results were stunningly different. Below is a diagram using the same number of pools which I described in the spring. This time, however, 42 of the pools are dry, and only 26 are full of water.
The number of Olympic-sized swimming pools that could be filled with water from the top 12 inches of soil found in late August 2018 at Tryon Creek State Natural Area.
Where did it go?
There are probably three main fates for the missing water in the top 12” of soil. First, any water at or close to the surface could simply have evaporated. I have no idea how much this would amount to, but in the top 1 to 2 inches of soil, I’m guessing this could be an important factor.
Subsurface Water Flow
Secondly, the water particularly in sloped areas, could have flowed down hill underground. Lateral underground movement of water is quite common. To illustrate this I poured several gallons of water onto the soil surface at a flat spot on the side of the Old Main Trail not too far from the Nature Center. After saturating the soil in this tiny area, I used a soil corer to create two 6” deep holes about an inch in diameter. I waited for several minutes until there was no freestanding water in either hole. Then I carefully poured water into the right hand hole, as seen in the picture below. Not surprisingly, the water flowed laterally underground, and appeared the other hole.
This subsurface water flow might be particularly important on the steep hillsides near the creek. To illustrate this effect, I found information online about two different watersheds. The first is the Tryon Creek watershed, which is the watershed in which the TCSNA is located. An analysis of this watershed by the City of Portland has shown that about 25% of it is made up of impermeable surfaces, like rooftops, sidewalks, driveways, streets, tennis courts and even swimming pools. An aerial photo of one small part of the watershed illustrates the extent of these impermeable surfaces.
Water falling on these impervious surfaces rapidly makes its way into Tryon Creek, thanks in part to storm sewer drains that are common in the city.
In contrast, the Fir Creek watershed, located in the vicinity of the Bull Run Reservoir in the foothills of the Cascades east of Portland is almost completely forested, with the only impermeable surfaces being a few roads in the area. These two watersheds are roughly similar in size.
The differences in the surfaces of these two watersheds creates an enormous difference in the water flow in the major creeks of the watershed. These differences are illustrated using data from the same “rain event” in both watersheds.
In this graph you can see that immediately after each large rainfall event that there is a sharp peak in the water flow in Tryon Creek. This sharp peak is followed by a slow decline in the water flow of the creek. It seems reasonable that the brief sharp peak in the creek depth is water running off the impermeable surfaces found in the watershed, and being quickly dumped into the creek by the storm sewer systems. The slower decline following the sharp peak, is, I assume, water actually slowly flowing through the soil and into the creek.
In contrast to the water flow in Tryon Creek, in the Fir Creek system, there is a slow but significant increase in the stream flow following the rains. I suspect this is because the water in this watershed all has to gradually seep through the soil, and slowly make its way down to the creek.
Water Usage by Plants
Thirdly, the water could have been extracted from the soil by the roots of plants, and subsequently evaporated from plant leaves. This would be one way in which soil water at some depths could be lost to the atmosphere. In studies2 of water usage by Douglas-fir (Pseudotsuga menziesii), for example, it was reported that a 60-foot tall tree with an 8 inch diameter used 5 gallons of water per day. A 91 foot tall Douglas-fir with a 14 inch diameter used 16 gallons per day. Our forest has numerous trees this big and bigger, so their water usage in summer for the forest as a whole could be more than we might first imagine.
Living as we do in an area with relatively dry summers and wet winters we could see dramatic changes from climate change. If we have a winter with subnormal amounts of rain, and warmer than average summers, there could be a large die off of moisture-loving plants which have lived in this area for some time. They will of course, be replaced with other plants, but the transition could be difficult.
2Wullschletter, Stan D., F. C. Meinzer and R. A. Vertessy. 1998. A review of whole-plant water use studies in trees. Tree Physiology.
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!
By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester
Fungi (singular = fungus) are one of the oldest types of living organisms on earth, dating back approximately 1 Billion years. It may be slightly easier to grasp if I say that fungi have been around approximately 12 times longer than the earliest primate ancestors of humans. The fungi have used their time to develop diverse, and sometimes complex lifestyles!
The basic building block of fungi is a hypha (plural = hyphae) which is basically a long branching fungal thread. They can be seen in the picture below. This growth was on the underside of a leaf that was lying on the damp soil. The hyphae are attached to both the cottonwood (Populus balsamifera ssp. trichocarpa) leaf and a Douglas-fir (Pseudotsuga menziesii) needle. The hyphae are sometimes collectively referred to as mycelium (plural = mycelia).
Fungi, unlike plants, do not make their own food. This has led many fungi to adopt one of three lifestyles; a) a decayer of non-living organic matter; b) a parasite/disease of living organisms; c) a helpful life-partner of another organism. All three of these life styles can be found at Tryon Creek State Natural Area (TSCNA).
Fungi as Recyclers
Fungi at TCSNA recycle (“decay”) many things, as pointed out in my Naturalist Note of October 2015. This can be thought of as their “rotting” function. This is nicely illustrated in the above photo, where the fungi are probably rotting both the leaf and the needle. Rotting releases nutrients in the organic matter to be re-used by other organisms. Unfortunately, some of the most obvious examples of this at TCSNA are fungi which are decaying dog feces (a. k. a. “poop”) left behind by dogs tended by those few people with apparently little regard for either the park or other visitors.
Fungi as parasites or disease
Attacking dead things is one lifestyle, being a parasite, or disease, is quite another. If you’ve ever had “athlete’s foot” you know first-hand about fungi causing diseases. Some of the fungi at TCSNA are diseases too. One tree disease is caused by the honey fungus (Armillaria mellea). They produce thick black shoestring-like structures called “rhizomorphs” under the bark of this log (see below) alongside Old Main Trail. Rhizomorphs are typical of the honey fungus. Species that are rated as “highly susceptible” to this fungal disease include our grand fir (Abies amabilis), Douglas-fir and western hemlock (Tsuga heterophylla).
Fungi as life partners
Sometimes fungi will form a close, often physically interwoven relationship with another organism that benefits both of them. A relationship that benefits both partners is called “mutualism” which is a specific type of symbiosis. One of the most common mutualistic relationships fungi form is with forest plants, including most trees. Fungi will grow on, or sometimes into, the roots of plants, forming structures called “mycorrhizae” (from the Greek “fungus root”).” Long fungal hyphae will extend out from the mycorrhizae into the soil. In this relationship, the plant provides the fungi with food (think “sugar”). In return, using chemical means the plant does not have, the fungi very efficiently extracts nutrients from the soil, especially phosphorus, and transports it to the plant.
Another advantage to the plant is that mycorrhizal fungal mycelium are dramatically smaller in diameter than the plant’s own roots. It takes less energy to build the mycelium than it would take to build its own roots. Thus for the same expenditure of energy on the part of the plant, it can tap into a much greater volume of soil by using the finer fungal threads. Over 2,000 species of fungus have been identified as potential mycorrhizal partners of Douglas-fir.
The coral fungus shown below is one of the fungi found at TCSNA that can have a mycorrhizal relationship with many tree species.
Another totally different kind of symbiosis, is when a fungus lives with an algae to form what we call a lichen. The fungus does a great job of providing moisture for the algae and the algae is able to photosynthesize (create sugar) which supports the fungus. There are thousands of species of lichen world-wide, but they have been grouped by their form into several different types. The fruticose lichen has lots of branch-like structures. The crustose lichen often looks like a thick layer of paint, and the foliose types have what looks like primitive leaves.
In the lichen, only the fungus reproduces sexually, and if some algae cells happen to cling to the spore as it floats away, great; otherwise, when the fungus lands, it will have to find some new algae with which to start a new lichen.
Fungi use chemical warfare
You don’t survive a billion years without picking up a few tricks along the way. Fungi have developed a broad array of chemical weapons in their fight for survival. Some fungi have been found to produce chemicals which inhibit competing organisms, like bacteria and other fungi, from growing near the fungus. Recall that the medicine penicillin was originally isolated from a fungus.
Some of these chemicals are also very effective in killing cancer cells. A chemical extracted from yew bark, taxol, has been known for years to effectively treat some breast cancers. Researchers have recently discovered that a fungus growing inside the yew bark, Taxomyces andreanae, produces the chemical taxol. Whether or not the yew tree itself also produces the chemical is not clear.
“By the sword you did your work, and by the sword you die”
The sentiment above, expressed by the Greek playwright Aeschylus in the 5th century BCE, applies to fungi as well as people. Just as fungi sometimes use chemical warfare against other organisms, sometimes chemical warfare is used against fungi too. TCSNA’s garlic mustard (Alliaria petiolata), an invasive plant native to Europe, produces and releases chemicals to stifle fungal growth. Since an overwhelming majority of plants are mycorrhizal, killing fungi interferes with the growth of plants that would otherwise compete with garlic mustard. Garlic mustard itself is one of a small group of plants that doesn’t have mycorrhizae.
One the principal chemicals released by the garlic mustard is allyl isothiocyanate. This chemical is released into the soil, and is toxic to the fungi located in the soil. Interestingly enough, in garlic mustard’s native Europe, the soil fungi are resistant to the garlic mustard’s chemical. Apparently our native fungi haven’t developed that resistance yet.
And sometimes life gets complicated!
There are a few fungi which have a lifestyle which is one of the most complicated of any organism on earth. These are called “heteroecious rust fungi.” These fungi are plant diseases. Their unique characteristic is that they need to use two species of plants to complete their life cycle. One of these fungal species that we may have at TCSNA is the “common fir-bracken rust” (Uredinopsis pteridis). This fungi spends part of its life cycle growing on bracken fern (Pteridium aquilinum) and the other part on grand fir.
I have no proof that we have this disease at TCSNA, but since we have both hosts here, it is a distinct possibility. Furthermore, this fungus sequentially produces not one, not two, but five different kinds of spores during its life cycle. Of the different spore types, some are produced only on the fern, and the others are produced only on the grand fir. Frankly, this complicated a life cycle boggles my mind. The two questions that plague me are: 1) How did this complicated life cycle ever get started? and 2) What conceivable advantage is there to the fungi in needing two hosts? The answers have eluded me.
The fungal internet
Human’s internet is a johnny-come-lately compared to the “internet” that fungi developed long ago. Strands of fungus often connect the root systems of two trees in the forest. The trees don’t even have to be the same species. The overall results is that fungi of one species or another, connect almost all the trees in the forest. Something like this:
It appears that fungi connect nearly every tree in the forest with other trees. While there is clear evidence that some small amount of sugars are passed from tree to tree, this fungal internet may have a far more interesting function.
Two different studies have found that plants apparently transfer “information” from one to another via their interconnecting fungi. In one study, some plants were deliberately infected with a fungal disease (not one that creates mycorrhizae). Researchers found that if a neighboring uninfected plant was connected via mycelium to the infected plant, it was dramatically less likely to catch the disease, than if the uninfected plant was NOT connected to an infected plant. It appeared that the mycelium was passing along a message that said, “Hey this disease is coming around, better get ready to resist!”
In a second study, the same basic effect was found when one plant was infected with aphids. The uninfected plants appear to get some signal through the mycelium from the infected plants, and its anti-aphid defenses kicked into gear before they were actually attacked by the aphids.
As you can see, the fungi of TCSNA are themselves complex and terrifically creative organisms. They play many important roles in our forest, by decomposing organic matter, acting as diseases, and forming mutually beneficial relationships with other organisms. They are the hidden partners in making our park a great place to enjoy nature.