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.

 

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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.

 

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

 

 

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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.

 

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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!

 

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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.

 

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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.

 

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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.
 

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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.

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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.

 

 

Big Hairy Deal!

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester

 

If you’re reading this, there’s an excellent chance that you have hair!  Well, you’re not alone!  Amazingly enough, many species of plants have “hair” too.  Technically, plant hairs are called “trichomes” and they’re different from mammalian hair in many ways.  They come in a variety of shapes and sizes, and perform many different functions.  The plants at Tryon Creek State Natural Area (TCSNA) have a variety of different kinds of trichomes.  Based on their physical properties, trichomes can protect plants from a variety of herbivores, reduce the loss of water and help spread the plant’s seeds.

 

Simple Plant Hairs     

 Let’s start out with the basic plant trichome.  These simple trichomes can be found, for example, on the petiole (“petiole” is the little stem that attaches the leaf blade to the branch) of TCSNA’s own red elderberry (Sambucus racemosa L. var. racemosa), as shown below.  These are simple, straight, unbranched hairs.

 

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Trichomes on a red elderberry petiole.

 

Plants, like most things in nature, are rarely frivolous.  If they expend the energy to produce plant hairs, those hairs most likely have a purpose.  One of the benefits of plant hairs is that they help reduce the rate of water loss from the plant.  Imagine a water molecule trying to escape from the elderberry pictured above.  The thicket of plant hairs on the stem dramatically slows down air movement right at the surface of the plant.  This mass of plant hairs is essentially a maze that the escaping water molecules have to slowly wander through before it leaves the plant.

To demonstrate this effect, I set up the following demonstration.  I took two small identical plastic tubs and completely filled them with water.  The first tub (pictured below) is totally open to the atmosphere.

 

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Open tub of water

 

For the second tub, I inserted a scrub brush, bristle side up, into the top of the tub.  The bristles of the brush created a maze similar to that created by plant hairs.  The water molecules had to move through this maze in order to escape (evaporate) from the tub of water.  And, yes, just like in plants, it did slightly reduce the open surface area of the water.

 

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Tub of water “with hairs”

 

I weighed the containers as shown before the experiment started.  After 36 hours of evaporation, I weighed the containers again.  The open container lost 39 grams of water, while the “hairy” container lost only 25 grams of water, 64% as much as the open container.

 

Get a Grip!

Some of the trichomes found in the plant world are simple, but not straight.  A good example found at TCSNA is the seed of the bedstraw (a.k.a. “cleaver”) plant (Galium spp.).  The seed, which is shown below, is covered with stiff, curved trichomes.

 

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Bedstraw seed with hook-shaped hairs

 

In case you’re wondering why the seed has these hook-shaped hairs, take a look at the picture below.

 

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Bedstraw seeds clinging to my shirt

 

The hook-shaped hairs allow the seeds to attach themselves to some innocent passing animal and hitch a ride to a new location.  Presumably they will be brushed off, or rub off somewhere after the passing human or other animal has traveled some distance and “voilà” the plant spreads itself to a new growing place.

 

En garde!

Plant hairs can defend against insects and other pests that want to eat the plants.  Sometimes, the sheer density of the hairs can serve as a deterrent to hungry herbivores.  Some insects might not be able to get through the hairs.  Some larger herbivores might just experience the hairs as “sharp pokey things” and decide to leave the plant alone.  A good example is the ultra-hairy seed of TCSNA’s bigleaf maple (Acer macrophyllum) as seen below.

 

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Seed of bigleaf maple

 

Sometimes, defensive plant hairs are a little more complicated.  One of the premier examples here at TCSNA is our beloved stinging nettle (Urtica dioica) which is pictured below.  The stinging nettle uses some of its plant hairs defensively.  The larger trichomes have a largely silica (like glass) hollow needle (blue arrow) mounted on a relatively soft green pedestal (red arrow) which contains toxins.  When some animal carelessly brushes against it, the tip of the needle breaks off and the movement of the animal against the plant bends the needle over, squeezing the toxin out of the green tissue at the base of the needle.  The toxin is thus injected into the offending animal.  The toxins in this species include histamine, acetylcholine, serotonin, and formic acid.  Typically they cause an itching sensation that for most people lasts no more than 24 hours.  Note that the stinging nettle also has much smaller hairs (yellow arrow) that are common on many plants.

 

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Stinging nettle petiole showing two types of plant trichomes.

 

While humans tend to be very sensitive to stinging nettle, apparently it isn’t 100% effective against all animals.  The banana slug (Ariolimax columbianus) pictured below crawling on stinging nettle seemed to be pretty calm and unconcerned by the trichomes.  It may be that the slug is either immune to the chemicals in the stinging nettle, or its famous slime layer is protecting it or it moves so gently that it doesn’t break the nettle’s needles!

 

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Banana slug crawling on stinging nettle near Old Main Trail.

 

“Fancy” Hairs

Human hairs are all unbranched.  This is not necessarily so for plant hairs.  The English Ivy (Hedera helix) has hairs that are branched.  The pictures below show these branched hairs from two different perspectives.

 

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Branched hairs of English ivy, top view.

 

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Branches hairs of English ivy, side view

 

Glandular Hairs

Finally, there are glandular hairs, which produce chemicals in a small gland at the tip of the hair.  One of the most interesting examples at TCSNA is the invasive plant commonly known as “herb Robert” (Geranium robertianum).  Another name for this species is “stinky geranium.”  If you ever pulled one of these plants, you’ll know why it’s called stinky geranium.  On the tips of the hairs (blue arrow) on the stem below, you can see a small red dot.  This red dot is actually a gland that produces the stinky chemical.  One of the traditional ways humans have used the chemical produced by herb Robert was to rub it on their skin to repel mosquitos.  It probably keeps insects away from the plant as well.

 

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Glandular trichomes on herb Robert with one of the glands indicated by the blue arrow.

 

A second example of glandular hairs on a plant at TCSNA is hazel (Corylus spp.)  Both of the hazel species that we have at the park have a significant number of glandular hairs, as shown in the photo below.  The chemicals are located in the brown tips of the hairs.  In both pictures below note that in addition to the glandular trichomes, the hazel also sports a large number of very small hairs on the midrib on the leaf.

 

 

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Single glandular hair of hazel

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Many glandular hairs on mid-rib of hazel leaf

 

Many interesting chemicals are produced by glandular hairs on plants.  The trichomes of the sweet wormwood plant (Artemisia annua), which is not found at TCSNA, produce the chemical “artemisinin” which is an effective drug against malaria.  And the psychoactive chemicals in marijuana (Cannabis sativa) are produced in the tips of the plant hairs of that species.

 

All in all, the hairs on plants are quite diverse, and have many functions.  As has shown here, plant hairs can slow water loss, help spread the seeds to new locations, and protect the plant from herbivores.  For the plants, the many functions of these trichomes do indeed make them a big hairy deal!

Fungi: The Amazing Ancients

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).

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White fungal hyphae on the underside of a decaying black cottonwood leaf

 

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 decaying dog feces alongside Old Main Trail

Fungi decaying dog feces alongside Old Main Trail

 

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).

Black rhizomorphs of Armillaria mellea often grow between the wood and the bark

Black rhizomorphs of Armillaria mellea often grow between the wood and the bark

 

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.

Coral fungus fruiting bodies

Coral fungus fruiting bodies

 

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.

Fruticose lichen on a stick

 

Crustose lichen on tree bark

Crustose lichen on tree bark

 

Foliose lichen on a branch which is resting on a log

Foliose lichen on a branch which is resting on a log

                                                

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.

 

Garlic mustard – First year plants near the North Horse Trail

Garlic mustard – First year plants near the North Horse Trail

 

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.

 

Left: Bracken fern near TCSNA bike path. Right: Needles and cones of grand fir near Cedar Trail

Left: Bracken fern near TCSNA bike path. Right: Needles and cones of grand fir near Cedar Trail

 

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:

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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.

 

Fascinating Fungi

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.

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