By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
The plants growing at Tryon Creek State Natural Area (TCSNA) require a supply of nutrients to stay healthy and keep growing. An important part of supplying those nutrients is the decay of dead organic matter like leaves and branches. This decay process releases the chemicals in the dead leaves and branches so those nutrients can be reused by plants that are still growing.
To study this process, I collected leaves, branches or cone scales of several species of trees found at TCSNA in September 2014. I only collected fresh materials which had recently fallen to the ground. Within two days I placed these in wire mesh (screen) “envelopes” and fastened the envelopes to the ground with nails. During the first part of the study I took photographs of the envelopes on a monthly or quarterly basis, but starting in September of 2016 I switched to once-a-year monitoring. The results after one and two years have already been published in earlier Naturalist Notes.
The one-, two- and three-year end results are presented here. While I had two envelopes for each of the materials, I only selected the most photogenic envelope for inclusion in this report.
Red Alder (Alnus rubra) Leaves
Red alder is a common tree at TCSNA, and is renowned for dropping its high nitrogen leaves onto the ground while they are still green. The results from this study are seen in the photos below.
One university research project studying the decay of dead red alder leaves indicated that 93% of the nitrogen in the alder leaves was released into the soil via the decay process the first year. The same study found that 91% of the calcium and 97% of the potassium (both key nutrients) were also released during the first year of leaf decay1. This relatively rapid decay of the red alder leaves was attributed to the fact that they generally contain higher levels of nutrients than most trees, thus nourishing the decay organisms.
Western Redcedar (Thuja plicata) Branchlets
In sharp contrast to the red alder leaves, the western redcedar foliage contains lower levels of many nutrients, thus making it a somewhat less attractive food source for microorganisms. In addition, redcedar foliage and twigs contain many terpenes. Terpenes not only give the tree it’s distinctive “cedar smell,” but terpenes also have anti-fungal properties. The major terpene in western redcedar (α-thujone ) is shown below.
No wonder that the cedar is decaying a little more slowly than some of the other samples.
Bigleaf Maple (Acer macrophyllum) Leaves
With no special chemical defenses against fungi, and a fairly high nutrient content, the maple leaves are another fast decaying material.
Douglas-fir (Pseudotsuga menziesii) cone scales
These Douglas-fir cone scales were already lying on the ground at the time of collection. The cones they came from had probably been chewed apart by a squirrel looking for the nutritious seeds.
Superficially, the cone scales after three years look almost exactly like they did the day I put them in the bag. Obviously the scales are made up of a very hard material, not too much different than the wood in the main stem of the tree. Mother Nature made the cone scales very durable to protect the precious young seeds, and as a result, they are being recycled very slowly.
Again, the Douglas-fir twigs and foliage contain some terpenes similar to the terpenes found in the redcedar, and thus, they decay more slowly than the alder and maple leaves. Notwithstanding the resistance to decay, all the needles have fallen off the twigs.
The End Result
The nutrients within each of the samples used in this study will be released and then absorbed by living plants and fungus, helping the forest to grow the next generation of life. This study shows the enormous differences in the decay times of different kinds of tree litter. The softer materials, like the alder and maple leaves also have the highest nutrient content, and lowest concentration of anti-fungal chemicals. But, as the old saying goes, “All in good time!” All these nutrients will once again join living organisms, ensuring the continuation of TCSNA’s forest!
1Radwan, M. A., Constance A. Harrington and J. M. Kraft. 1984. Litterfall and nutrient returns in red alder stands in western Washington. Plant and Soil 79(3):343-351.
By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester
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!
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.
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:
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.
Not that ivy vines don’t grow large, especially when two or more vines merge together.
Ivy only had to develop a method of holding onto the tree. Voilà! The aerial rootlet, which adheres to the tree’s 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.
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.
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.
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:
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.
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!
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!
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.
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!
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.
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.
The effectiveness of polishing is shown in the “before and after” photos below.
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.
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.
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.