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English Ivy: Forest Invader

By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester

 Photo 1

This Naturalist Note is dedicated to Phil Hamilton who passed away on June 12.  Phil devoted more than 24,000 volunteer hours helping make Tryon Creek State Natural Area the wonderful place it is today.  He played many leadership and resource roles, but is perhaps best known as the ‘King of the Ivy Pullers.’  He not only pulled a lot of ivy himself, but led hundreds of groups of ivy pullers out into the park.  Every time I went out with him, he told me something brand new about the forest that I did not know before.  He was a great role model, and helped many people get started on the track of volunteering at Tryon Creek.  I, and I’m sure many others, will remember this dedicated, knowledgeable and hard-working man forever.  Thank you Phil!

 

 

If there was a vote on the most despised plant at Tryon Creek State Natural Area (TCSNA), ivy would win hands down.  This aggressive, invasive plant outcompetes and displaces many native plants.  In an area near the Red Fox Trail where the ivy completely covered the forest floor, I removed and measured the ivy in a three-foot by three-foot plot.  In that plot there were 285.8 linear feet of the ivy vine.  (Yes, it was really thick, in multiple layers!)  If (and thankfully, it doesn’t) this density of ivy covered all of TCSNA there would be enough ivy to wrap around the earth at the equator more than 6 times!

Photo 2

Ivy harvested from a 3 ft. x 3 ft. area of forest floor.

 

 

Ivy’s habit of climbing up tree trunks makes it difficult to ignore.  Not surprisingly, ivy has many special features that make it so successful.

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Ivy growing up a tree trunk near the Red Fox Trail.

 

 

Ivy:  The ingenious climber

Ivy needs sunlight to grow.  How does a plant get close to the sun?  Most trees, like our Douglas-fir (Pseudotsuga menziesii) develop a thick trunk that lifts their leaves up toward the sun.  Building the thick stem takes a lot of resources.  A study in western Washington showed that for 47-year-old Douglas-fir, 87% of the above ground biomass was in the trunk of the tree.  The major purpose of the tree trunk is to get the needles up into the sunlight where they can photosynthesize.  The ivy developed the habit of just climbing the tree trunks that were already there.  It saved itself all the energy required to develop a self-supporting stem.

 

I pulled down an ivy vine that was growing up the side of a tree.  The diameter of the ivy’s stem at ground level was 3/4 of an inch.  Twenty-one feet up the tree, it was not much smaller, as you can see below:

Photo 4

Cross section of a single ivy stem at ground level (left) and twenty-one feet high (right).

 

Since ivy doesn’t need a thick stem to hold itself erect, it uses its energy to grow taller.

In contrast, a western redcedar (Thuja plicata) only 10 feet tall growing along Old Main Trail had a basal diameter of 1.59 inches.  The redcedar needs this thick stem to hold itself up, while the ivy doesn’t.

Photo 5

Stem diameter a base of 21+ foot tall ivy and 10 foot tall western redceadar.

 

 

Not that ivy vines don’t grow large, especially when two or more vines merge together.

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Cross section of a large ivy vine with red arrows marking the pith (“center”) of the three original vines.

 

Ivy only had to develop a method of holding onto the tree.  Voilà!  The aerial rootlet, which adheres to the tree’s bark:

Photo 7

Ivy stem (blue arrow) with aerial rootlets (red arrows) clasping the tree bark.

 

Using these aerial rootlets, the ivy manages to climb up the trunk of trees into the light without having to expend the energy to develop a big, supportive stem.

 

Creating a Home for Others

While we rarely envision ivy as a benevolent plant, other organisms may have a different view.  As you can see in the photo below, sometimes the mass of ivy stems creeping up a tree is part of a community complex most frequently involving moss or licorice fern (Polypodium glycyrrhiza).  While removing ivy from a tree near the Red Fox Trail, I collected the sample (in cross section) shown below.  It is a combination of primarily ivy and licorice fern, with a hint of moss.

Photo 8

Mat of ivy stems and roots mixed with licorice fern stems (red arrows) and roots from trunk of red alder.

 

The mass of roots, stems and miscellaneous dirt measured about 7 cm (~2-1/2 inches) thick.

 

How much water might this hold?  I cut a 2-1/2” by 3-1/4” sample from the tree.  I soaked it overnight in water.  I weighed the wet sample and then let it air dry completely and weighed it again.  I calculated that a square foot of this material would hold slightly more than 2-1/4 quarts of water.  This is a mixed blessing.  While some of this is a nice reservoir of water for the licorice fern growing in this mass, it is also a significant weight burden for the tree.

 

To find out how much water might be stored in the mass of ivy roots and licorice fern, I did some calculations.  I measured the diameter of the trunk of a large fallen alder tree near the Middle Creek Trail at 10 foot intervals, up to 63 feet above ground, where it started branching out.   Based on this data, I calculated the surface area of the tree trunk.  If the entire surface of this tree trunk were covered like the sample above, the ivy/moss/licorice fern could potentially contain up to 1,520 lbs. of water.  That’s three-quarters of a ton of water.  Yikes!

 

Ivy:  It’s Tough

Every species of plant contains nutritious chemicals like sugar, cellulose and dozens of others.  This naturally attracts other species that don’t have the ability to capture solar energy to sustain themselves.  One of the keys to a plant’s survival is to protect itself from these organisms, which range from molds and insects, all the way to humans.  In the picture below, you can see the surviving remnants of leaves on one of TCSNA’s common shrubs.

Photo 9

Damaged leaves on dull Oregon grape (Mahonia nervosa)

 

To find out how effective ivy is in protecting itself, I conducted a survey in the fall of 2016.  I examined the leaves of three species of plants, and counted the number of leaves (or leaflets) that were damaged.  To minimize the possible effects of humans, I examined sites more than 10 feet from a trail.  (Confession: I don’t actually know what caused the damage; it might have been insects, diseases, a hailstorm or whatever.)  For each species, I examined leaves in two different places (for example, near Red Fox Trail and near Old Main Trail), to get an “average” value.

The results are presented below:

                                 Number of                  Total leaves           Percent of

Species                damaged leaves               examined           leaves damaged

Red Alder                   181                                  199                          90.0%

Oregon grape            375                                  559                          67.1%

Ivy                                  93                                  279                          33.3%

 

Ivy has less leaf damage, whatever the cause, than either the red alder or the Oregon grape.  Good for the ivy!

 

Ivy is a Persistent Grower

Every plant has a growing season, and for ivy, it’s long.  To determine how long into the fall/winter this plant might grow, I measured the growth of an individual ivy stem along the Red Fox Trail.  The data shows that ivy continues growing quite late in the year.

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In contrast to the ivy, on September 28, one of the Indian plum (Oemleria cerasiformis) plants I was monitoring in that area was completely bare of leaves, while the other Indian plum in that area had dropped about 98% of its leaves.

 

Ivy’s Secret Strategy

One of ivy’s secret strategies is that virtually every place along the stem where there is a leaf, there is the potential to grow roots.  That is seen in the photo below:

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Ivy roots developed at every node on this stem.

 

Should the stem of this ivy plant be broken, no sweat!  Every part of the stem has its own root system and can stay alive.  This is in contrast to most woody plants which only produce roots at a single point in the plant.

 

English Ivy really isn’t that bad (a tidbit for geeks!)

It turns out that much, if not most, of the ivy that we have at the park really isn’t English ivy (Hedera helix); it’s Irish ivy (Hedera hibernica).  Not that the other plants care!

 

The key reliable morphological feature that discriminates between the two species are the miniature hairs that grow in clusters on the plant.  The Irish ivy hairs are in small clusters lying flat on the plant’s surface, while English ivy hairs are in larger clusters and stand erect.  The microphotographs below of plants collected at TCSNA shows the difference.

Photo 12

Left: Flat “hairs” on Irish ivy; Right: Erect “hair” clusters on English ivy.

 

To further complicate things, hybrids of English and Irish ivy have been discovered and….  Okay, I’ll quit now!

 

The Ivies:  Green Success Stories

The ivies in the genus Hedera are very successful plants.  They can grow tall without having to use their own stem to support themselves.  When hacked into pieces, many of the pieces are able to stay alive and become a whole new plant.  They also appear more resistant to disease and predation than many of TCSNA’s other plants.  They have a longer growing season than many of our native plants.  All of this spells success for the plant, and lots of work for our ivy pullers who are trying to encourage the growth of native plants by reducing the resource competition from the ivy!

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Slime Molds: The Weirdos of the Forest

By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester

 

Some strange things live in the forest at Tryon Creek State Natural Area (TCSNA) but for my money, none is stranger than the organisms known as slime molds. Taxonomists, folks who specialize in classifying organisms, haven’t all agreed on how to classify slime molds. They do, however, all agree that slime molds are clearly neither plants, animals, fungi nor bacteria. Slime molds are fascinating creatures because they have a very strange life cycle, and a highly unusual “body”. This note focuses only on the plasmodial slime molds, which are the type you will probably see at TCSNA. [Important: The slime mold names used in this note represent my best efforts at identifying these creatures, based on their strong similarity to photos on the internet.]

 

Where do slime molds grow?

The best place to find slime molds at TCSNA is on rotting wood. Old logs, tree stumps, or dead standing trees are prime candidates. This is because the primary foods for slime molds are bacteria and fungi. These are abundant in dead wood. Experts say the best times to find these slime molds is either spring or fall, when the forest is fairly damp. The slime molds pictured in this note were found at TCSNA in April, July, September and November.

 

What’s so weird about slime molds?

The weirdest thing about slime molds is their dramatic changes in shape over the course of their life cycle. Let’s start with the point in the life cycle which gives these organisms their name. The most active adult stage of the slime mold is when it looks like (surprise, surprise) slime! This nearly formless stage is called the plasmodial stage. At the risk of being indelicate, the adult slime mold in this stage looks like someone with serious nasal congestion blew their nose onto a log. This stage looks a little “blob-y” and has a distinct “wet” appearance. The plasmodium stage of life is the diploid stage where the slime mold has chromosomes from both parents, just like you. The example pictured below was on a decaying tree trunk that was lying on the ground near the West Horse Loop Trail.

 

Photo 1

Unknown species of slime mold in plasmodial stage on rotting log

 

These blobs of life are unusual in that they are giant cells with many thousands of nuclei in each cell. For most life forms, one nucleus per cell is the rule. Also, at this stage, there is a thin cell membrane, but no rigid cell wall. The big advantage to having giant wall free cells is that these plasmodia can move by streaming the cell contents (cytoplasm) from one end of the plasmodium to the other end. The plasmodium will move in the direction that the streaming cytoplasm is heading. Laboratory studies have observed slime molds moving at approximately 1 inch per day towards concentrations of food.

When food starts to become scarce, the slime mold moves into the next stage of life. This stage is called a sporangium. The sporangium, as you might guess, is the stage that produces the spores. The forms of the sporangium differ greatly, depending on the species of slime mold.

 

How does the sporangium develop?

There are many different sizes, shapes and colors of sporangia, depending on the species of slime mold. Examples I’ve found at TCSNA are included below.

The series of photos below shows the development of a single sporangium found on a standing dead tree along the Trillium Trail is shown. Unfortunately, I found the sporangium when it was completely developed. This was formed by a plasmodial mass similar to the one pictured above. A tough shell develops to protect the developing spores on the inside. This sporangium is the species of slime mold called “false puffball”. Its scientific name is Enteridium lycoperdon. The most striking thing about this sporangium is that in my entire life I have never seen a natural object that has looked so much like plastic. Measured vertically along the trunk of the tree, it is about 3 inches long.

 

Photo 2

Slime mold near Trillium Trail– April 02, 2016

 

Just one day later, the surface of the sporangium has started to crack apart. The interior of the sporangium is filled with small brown spores. This particular sporangium was growing very close to the trail. I suspect the yellowish area which is oozing just a little yellow fluid is in fact a wound inflicted by a curious visitor to the park!

 

Photo 3

Trillium Trail slime mold– April 03, 2016– red arrows point to apparent wound

 

After three additional days, the surface of the sporangium is starting to seriously deteriorate, exposing even more brown spores.

 

Photo 4

Trillium Trail slime mold– April 06, 2016

 

In just an additional 3 days, the surface of the sporangium is almost completely gone, and many of the spores have been washed or blown away. Now the spores will germinate and produce     single celled amoeba-like cells that crawl around. These cells are the functional equivalent of human egg and sperm cells. These amoeba-like cells will find and fuse with a compatible amoeba-like cell. Then this fused cell will grow to become a new plasmodium, restarting the cycle.

 

Photo 5

Trillium Trail slime mold– April 09, 2016

 

The photo below gives you an idea of what the interior of this slime mold sporangia contains.

 

Photo 6

Brown powdery spots from inside the sporangium

 

While observing the above slime mold, I noticed some insects on its surface. As I approached quite close to take photos, the insects boldly maintained their positions. I sent this picture to Josh Vlach, an entomologist with the Oregon Department of Agriculture. He indicated this insect “looks like a Mycetophilidae possibly a species of Mycetophila”. Mycetophilidae is a family of insects, while the Mycetophila is a genus within that family. The common name for this group of insects is “fungus gnats.” This type of insects oftentimes lay their eggs in either mushrooms or slime molds. The developing larvae eat the mushroom or slime mold. One of these insects appears in the picture below.

 

Photo 7

A fungus gnat investigating a slime mold sporangium

 

Are there other kinds of slime mold at TCSNA?

Yes, I’ve spotted several other kinds of slime molds at Tryon Creek. Below is an example of a slime mold in an advanced stage of spore production. It was on the side of a downed log just off the Old Main Trail. The cluster of spore producing bodies seem to be resting on a thin sheet of shiny material that looks like dried slug slime. The entire cluster is 9 inches horizontally, and 6-1/2 inches vertically. The thickness of these spore clusters is less than 1 inch. When touched, they easily broke into a dark brown powder. These appear to be the species Tubifera ferruginosa, the red raspberry slime mold. In a younger stage, which I clearly missed, they are bright red.

 

Photo 8

Mature patch of ‘red raspberry’ slime mold– July 06, 2015

 

In the close-up below, you can see more detail of the structure of this slime mold.

 

Photo 9

Close-up of mature red raspberry slime mold reproductive structures

 

Next is the dog vomit slime mold. (I don’t name ‘em, I just report ‘em!) For once, you might like the Latin name better – Fuligo septica. Below is the sporangium of this colorful slime mold, which I found on a fallen log next to the Middle Creek Trail. The outer covering of the sporangium is just starting to break apart, revealing the brown spore bearing parts of the slime mold. On the moss just below the sporangium, you can see a few remnants of plasmodial strands that didn’t quite make it into the sporangium.

 

Photo 10

“Dog vomit” slime mold on fallen log on the side of Middle Creek Trail– September 13, 2014

 

Below is a close-up of the surface of the dog vomit slime mold. It is substantially different in both color and texture from the first slime mold pictured in this note.

 

Photo 11

Close-up of surface of dog vomit slime mold

 

Slime molds are an amazingly diverse group of organisms, and the next species testifies to that. The photo below appears to be a slime mold in the genus Trichia. The plasmodium, the white slimy part, and the sporangia, the orange balls on a stalk, coexist. The orange blobs bear the spores for this slime mold.

 

Photo 12

Slime mold found on an old stump on Middle Creek Trail– November 20, 2014

 

Not only are the sporangia of this species dramatically different in appearance, they also differ in size. The next photo compares the sporangia to my thumbnail.

 

Photo 13

My thumbnail provides size perspective

 

So what’s the lesson here?

The slime molds really are the weirdos of the forest, and trust me, this note only scratches the surface of that weirdness. They remind us that there are many ways to be successful. The slime molds eat the bacteria, and the larvae of the gnat fly eat the slime molds, and many things eat the gnat files. Every creature in creation is linked together, and we would be wise to remember that.

 

Native American Uses of the Forest

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester

 

For thousands of years before settlers from the eastern United States or Europe arrived in the vicinity of what is now Tryon Creek State Natural Area (TCSNA), Native Americans called this forest home. The Native Americans used resources ranging from rocks to trees to animals. However, the basis for much of the Native American life was the plant life of this area. They relied on the forest and waterways for everything; food, medicine, tools, clothes, everything!

What kinds of plants did they eat?

There were lots of plants and fruits the Native Americans ate. Some of the more tasty items were the berries from the forest, like the salal (Gaultheria shallon) berries. Pictured below are the plant and berries. I’ve planted salal in my front yard, and they are delicious on my morning cereal!

1

Salal plant, with salal berries in the inset at lower left

 

Another food the Native Americans sometimes ate were the berries of the Oregon grape (Mahonia nervosa). In the photo below, the blue-colored berries are almost ready to eat, while the greenish ones have a way to go before they are ripe.

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Oregon grape berries starting to ripen

 

I’ve tasted Oregon grape berries too. My taste buds’ response was, o-o-o-o-kay! I think they’re about half way between yummy and yucky. According to ethnobotanists, people who study how different groups of people use plants, the Native Americans would sometimes mash the fruits of the salal and Oregon grape together. In this way, they had a greater total quantity of food, which still tasted “kind of” good.

 

Another category of food plants is represented by the skunk cabbage (Lysichitum americanus) pictured below. This plant has a large underground tuber (note: potatoes are also tubers). Unfortunately, the skunk cabbage tuber tastes awful. It had to be specially prepared to become even edible. Ethnobotanists refer to this as a “starvation food” meaning that you only ate it when the alternative was starvation. If you’ve ever smelled a skunk cabbage in the spring, you understand why it wouldn’t necessarily pop into your mind as a good food item!

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Skunk cabbage plant and flower

What kind of medicine is in the forest?

For the Native Americans, the forest was their drugstore. Just one of the many medicinal plants used by some Native Americans was the licorice fern (Polypodium glycyrrhiza). The pictures below show the licorice fern growing on the side of a tree at TCSNA and the second photo shows a cleaned-up licorice fern plant that was growing on a branch that was blown down during a windstorm. The rhizome can be thought of as a perennial stem, while the leaves come and go with the seasons.

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Licorice fern growing on a tree trunk

 

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Licorice fern after removing the surrounding moss

 

The Native Americans cleaned up the rhizome of the licorice fern and chewed it as a cough and sore throat remedy. Once when I was not at TCSNA, I cleaned up a licorice fern rhizome and chewed it a bit. It does taste faintly like licorice. Within 30 seconds of starting to chew the rhizome, I got a tingle right in the back of my throat. Although I was perfectly healthy at the time, the fern was definitely affecting me. It would have been interesting to see the effect if I’d had a cold or sore throat.

 

What kind of tools did they find in the forest?

One of the tools the Native Americans found in the forest was the horsetail (Equisetum spp.), pictured below. This primitive plant contains a lot of silica crystals. Silica is the most common material found in sand. The Native Americans used this as a “natural sandpaper” for finishing their wooden tools. The effectiveness of this tool can be demonstrated by using it to polish a penny.

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Equisetum and polishing a penny with Equisetum

 

The effectiveness of polishing is shown in the “before and after” photos below.

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Two unpolished pennies (left)        Far right polished for 2 min. with Equisetum.

 

What kind of clothes did they make from forest plants?

The western redcedar tree (Thuja plicata) had many uses. To give just one example, its bark is very fibrous. With careful harvesting and care it can be used to produce everything from rope to clothes. Pictured below is a cedar bark rain hat. These were widely made and used by the Native Americans on the Pacific coast. According to some sources, they would sometimes treat this hat with pitch to make it even more water repellent.

 

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Native American cedar bark rain hat

 

But of all the clothing that the Native Americans made from forest plants, the one that always intrigued me was that they used moss for baby diapers. I wondered how well those would work. Strictly as a public service, I decided to run an experiment and find out.

You personally tested moss as diapers? Seriously?

Before your imagination runs wild (it may already be too late), let me explain. I took samples of five water-absorbing things:

  • A major brand of modern disposable diaper
  • A sponge
  • A pile of moss
  • A traditional cloth diaper
  • A bunch of paper towels

 

I weighed each item dry, making sure I had between 60 grams and 90 grams of each material (this is about 2 to 3 ounces). I then soaked each item (separately) in water completely covering the test material with water for 15 minutes. Then I put each material on a sheet of screen to drain. When the drops of water falling out of the material were 10 or more seconds apart, I considered the material to be completely drained. I then weighed each item wet. I calculated “absorbency” by dividing the weight of water absorbed by the dry weight of the material.

 

The results are displayed in the chart below.

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Modern diapers with their SAP (Super Absorbent Polymer) ingredient can absorb more than 80 times their weight in liquid! But let’s cut to the chase. I was fascinated to see that moss, the key ingredient in the Native American diaper could absorb 7.4 times its dry weight in water. In contrast, a classic 100% cotton, all-cloth diaper can only absorb 3.5 times its own dry weight in water. So the Native Americans were using the superior diapering material! Wow!

 

At home in the forest!

To the Native Americans, the forest was their home, their grocery store, their pharmacy, their hardware store, their everything! They adapted to their environment to meet all their needs.

 

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