Layers of a forest

I spend a lot of time drawing during some of my classroom programs.  I draw to illustrate key concepts such as food chains and trophic levels.  I draw to show the parts of plants and animals.  I draw to show students what they are expected to do on activity sheets.   I draw to explain things in a way that I cannot with words alone.

I especially draw during my program on forest habitats.  During this program I usually end up drawing an entire forest from the tops of the trees on down to the soil beneath our feet.  Sometimes these drawings are done on whiteboards with dry-erase markers.  Other times those drawings are done on paper and projected via a document camera to an interactive whiteboard.  I never take these drawings with me.

Last Wednesday (13 DEC) I didn't have any school programs;  I decided to draw the layers of a forest and scan the drawings so I can access them any time I want.  Here are the drawings.

First up is the canopy.  The canopy is made up of the tallest mature trees in the forest.  Here in Mid-Michigan the canopy begins 20 to 30 feet off the ground and extends upwards to a height of 50 - 100 feet (or more) above the ground.  Some canopy trees include Red, Silver and Sugar Maples; Red and White Oaks; Green, White, and Black Ash; some Willows; Basswood; White and Red Pines;  Balsam Fir; Paper Birch; Hickories; etc..

Forest Canopy

Beneath the canopy is a second layer of trees known as the understory.  The understory is composed of two groups of trees.  Some trees in the understory are immature canopy trees - these trees are waiting for a space to open up in the canopy when a mature tree dies or falls over.  Other understory trees will never take a place in the canopy.  Instead, they have evolved to live in the shade provided by the canopy - making due with less sunlight.  Some trees in this category include Nannyberry, Hornbeams, Striped Maple, Speckled Alder, Redbud, etc..  Most of these trees top out at a maximum height of 15 to 30 feet.

Forest Canopy and Understory

Below the understory is a third layer of woody plants known as shrubs.  Unlike trees that have a single dominant trunk, shrubs typically branch out right at ground level.  Sometimes these branches droop enough to make contact with the ground and develop new roots.  Shrubs are often wider than they are tall.  Shrubs range in height from a few inches to about 15 feet.  Native shrubs in Mid-Michigan include Dogwoods, American Fly Honeysuckle, Witch Hazel, Winterberry, Spicebush, and more.

Forest Canopy, Understory, and Shrubs

Beneath the shrub layer we come to a layer of herbaceous plants.  Herbaceous plants are those plants that lack a woody stem such as ferns, grasses, wildflowers, and moss.  These plants range in height from less than an inch in height to about 10 feet - without a woody stem, it is very difficult for these plants to support their own weight above a certain height.  The majority of these species are below our eye-level.  Some of the more well-known herbaceous plants include Trilliums, Lilies, Sunflowers, Asters, and many more.  There are hundreds of species that fit in this category.

Lack of sunlight is a major challenger for herbaceous plants in a forest ecosystem.  The trees and shrubs above them my block as much as ninety-five percent of available light during the growing season.  To overcome this shortage, many herbaceous plants have developed strategies to ensure that they receive adequate sunlight to meet their energy needs.  Some species have evolved to make due with less sunlight.  A few species have developed into parasites that meet their energy needs by stealing sugars from other plants.  Many species have evolved to complete their annual cycle of growth and reproduction in early spring before the canopy leaves have fully developed, ensuring that their own energy needs are met while sunlight is readily available.

Forest Canopy, Understory, Shrubs, and Herbaceous Plants

We have finally come to the forest floor.  In a healthy forest, the forest floor is covered with a layer of organic debris including leaves, small branches (fine woody debris), and large branches and logs (coarse woody debris).  This layer of debris is filled with trillions of organisms working to break down all of this organic matter.  This includes invertebrate animals feeding on the debris and fungi and bacteria decomposing everything that is left.  Without the work of these decomposers the nutrients trapped in the organic debris would be unavailable for uptake by the layers of plants.

Forest Canopy, Understory, Shrubs, Herbaceous Plants, and Floor

Finally we come to a layer that we think very little of and know even less about - the subterranean layer.  This layer is composed of organic (the decomposed remains of living organisms) and mineral soils (rock that has broken down to the size of sand particles or smaller) with larger pieces of rock included in the mix.  This layer of soil may be only a few centimeters deep or may extend hundreds of feet deep before reaching the underlying bedrock.  The top couple of feet of soil are usually criss-crossed with an interlocking web of roots from trees, shrubs, and herbaceous plants.  The mycelium of fungi add their own root-like structures.  In addition to roots, this hidden world is home to untold numbers of invertebrate animals and bacteria.

Forest Canopy, Understory, Shrubs, Herbaceous Plants, Floor, and Subterranean Layers

The old saying "can't see the forest for the trees" is used to describe someone who gets so involved in details that they cannot see the big picture.  In a forest it is easy to look at the trees and fail to see that they are part of a much larger complex system.  Hopefully this article has helped you learn to "see the forest".

Project R.E.D. in Isabella County (22 September 2015)

I spent all day yesterday at a local Project R.E.D. event.

What is Project R.E.D.?

The R.E.D. in the name stands for Rural Education Day.  This is an event hosted by the local chapter of the Michigan Farm Bureau in locations around the state of Michigan.  This project is designed to expose 3rd and 4th grade students to various aspects of rural and farm life to which they may not have been exposed.

For these events, the Farm Bureau brigs in local experts to talk about various aspects of farming and natural resources.  Experts may be farmers, government employees, veterinarians, etc..  As an employee of the Isabella Conservation District, I was asked to come in and talk about soil.

Talking to students about soil types - photo by Leigha Shoaf

With the exception of a group of home-schooled students, the students that participated in the Isabella County Rural Education Day were 4th graders from schools in the Shepherd, Mt. Pleasant, and Beal City area.  I had worked with almost all of these students when they were in 3rd grade (and will visit most of their classrooms again later this year).

Students examining soil profiles - photo by Leigha Shoaf

Each group of students rotated through a series of stations, with only eleven minutes at each station.  At the conclusion of the eleven minutes, the horn on a semi-truck was sounded to indicate that it was time too rotate.

I missed this.  This student appears to be biting a lump of rock-hard clay - photo by Leigha Shoaf

Eleven minutes is not a long time.  It is barely enough time to give an introduction to soil, but because most of the students had already studied soils with me when they were in 3rd grade we were able to treat it as a review.  We talked about the various components that make up soil (minerals, organic matter, water, air, and microorganisms), the different different sizes of soil (sand, silt, and clay), and how the various combinations of those components and soil sizes either help or harm plant growth.  We also looked at soil profiles and handled samples of soil dug on site.

Explaining the properties of loamy soil - photo by Leigha Shoaf

I had a great time at this event and look forward to participating again in 2016.  Thanks to Leigha Shoaf for taking the photographs.  Leigha is an Outdoor Recreation major at Central Michigan University and is volunteering her time this semester to help me with classroom programs and gain some experience at the same time.

Soil Sedimentation Experiment - Sand, Silt, and Clay

One of the programs that I do in classrooms is called Soil Science.  During this program, students perform two experiments that show to show that soil particles come in different sizes. One of the experiments involves sorting a soil sample with a screen sieve - I detailed this experiment a little bit in a post from February 2014.

The other experiment that the students perform is a sedimentation test.

Here are the materials that the students use for this experiment.  Each group of students receives a test tube rack with test tubes filled halfway with soil - any clear container with a water-tight lid will work.  They also receive a bottle of water (these bottles have been refilled with tap water), a plastic spoon, and a small amount of ammonium aluminum sulfate (also called ammonium alum or just alum).

The soil in each test tube is different - I collected soil from four different locations for this experiment.

Sample #1 is from a sandbar along the Chippewa River and consists mostly of medium-grain sand, with some course sand, and small amounts of silt, clay, and organic matter.

Sample #2 came from the field behind the Conservation District Office.  It consists mainly of a fine- to medium-grain sand with very small amounts of silt, clay, and organic matter.

Sample #3 consists of a topsoil with medium- and fine-grained sand, with lots of silt and organic matter.

Sample #4 was dug up in the native pollinator garden at Winn Elementary and consists almost entirely of clay.

It may seem obvious, but the first step to this experiment is to uncap the test tubes.  Next a small amount of alum is added to each test tube.  Use the spoon to add an amount of alum equal is size to an M&M candy (an amount equal to about 1/4 inch in diameter) to each test tube.  The alum bonds to any organic matter in the soil and helps it float.

The next step is to fill the test tubes with water and cap them.

I tell the students not to fill the water entirely to the top of the test tube, but rather to stop at the lip just below the cap.  This allows you to see all of the results of your experiment without having them hidden by the cap.  The water will quickly infiltrate the soil samples that are composed mainly of sand.  The infiltration rates will be much slower in soils with higher concentrations of silt and clay.  In this case, test tube may need to be capped, shaken to mix the soil and water, and then refilled up to the same line as the other test tubes.

Once the water has infiltrated all of the soil samples and the test tubes have been refilled up to the "fill line" the test tubes are capped tightly.  The students then vigorously shake the test tube for about 30 seconds to a minute before placing it back in the rack.  In the classroom, we then typically allow the contents to settle for 15 to 20 minutes before examining the results.  During this time the soil that was mixed with the water settles.  The larger (heavier) particles sink faster than the smaller (lighter) particles.  This means that the soil will settle into distinct layers based on size.  The bottom layer will consist of sand particles of varying sizes.  This will be topped by a layer of silt.  Finally, if we allow the sample to sit long enough a layer of clay particles will settle on top of the silt - the clay usually is still suspended in the water after 20 minutes and may take as long as 24 hours to fully settle out.  Any small particles of organic matter in the soil will float to the top of the test tube - the alum bonds to the organic matter and helps it float.

Here are the results at various times.

At 15 seconds, the sand in the samples has already settled completely and the silt is also beginning to settle.

At 1 minute, Sample #1 has settled into distinct layers of sand and silt, with some clay still being in suspension.  Layer of sand can also be seen in Sample #2 and Sample #3.  Sample #4 remains almost entirely in suspension, with no visible settling.

Here are the samples at 2 minutes.  With back-lighting, it's easier to see how much has settled in each test tube.  Sample #1 is mostly clear.  Sample #2 still has a fair amount of clay in suspension.  Sample #3 has a large amount of organic matter floating at the top of the test tube.  Sample #4 still has not begun to visibly settle.

At 5 minutes, the clay particles in Samples #1, #2, and #3 have settled even more.  Sample #4 remains "as clear as mud".

At 10 minutes, Samples 1-3 are all clearer as clay settles out of them.  Organic matter can be seen floating in each of these samples.  Sample #4 still remains mostly in suspension.

At 20 minutes, Sample #4 has finally begun to settle out of solution.  The other samples continue to clear.

At 30 minutes, Sample #4 continues to settle out.  Sample #2 still has a significant amount of clay suspended in the water also.  Sample #1 and Sample #3 are mostly done settling at this time.

At 60 minutes, I moved the test tube rack to the window where it could sit undisturbed overnight.  As you can see Samples #1, #2, and #3 are mostly done settling at this point.  The test tube for Sample #2 has some discoloring to the plastic and is clearer than it looks.  Sample #4 has settled further.

The next photo shows the test tubes the following morning, 17 hours after starting the experiment.

As you can see in the above photograph, each sample has almost entirely settled out of suspension at this point.  The following four images are close-up photos of each sample showing the distinct layers that formed as the soil settled.

Here is Sample #1 after 17 hours of settling.  There is a distinct layer (bed) of coarse sand at the bottom of the test tube.  Above that is another layer consisting of medium- and fine-grained sand - these two are intermingles with some evidence of bedding.  Atop this layer is a thin layer consisting of silt and clay.  There is a very small amount of organic matter at the top of the test tube that is not visible in this photograph.

Sample #2 at 17 hours also shows distinct layers.  There is one large layer of intermixed fine and medium grain sand, topped with a thin layer of silt and clay.  There is a little bit of organic matter visible at the top of the test tube.

Sample #3 at 17 hours shows the most layers.  The bottom layer consists of a dark colored mix of medium- and fine-grained sand.  Above this bed is a layer of dark silt.  This is in turn topped by a bed of clay.  Finally there are two layers of organic matter - some of the heavier organic particles are resting atop the clay bed while others are floating at the top of the water.  The alum that was added to the test tube adheres to the organic matter and helps it float.  These organic particles are essentially neutrally buoyant and minor disturbances to the water cause some particles to sink and other to float upward.

Finally, Sample #4 at 17 hours shows no evidence of bedding.  Instead it consists of a single thick layer of clay particles.  These particles are still partially suspended in the water.  Two days after starting this experiment, this sample still looks as it did at 17 hours.

Soil Particle Sizes - Sand, Silt, and Clay

One of the programs that I do with students is called "Soil Science".  In this program we discuss the different materials that make up soil (minerals, organic matter, water, air, etc.) and the idea that soil particles come in different sizes.  To show that soil particles come in different sizes, the students perform two different experiments.

In the first experiment, the students perform a sedimentation test.  In this test, a sample of soil is placed in a plastic test tube.  A small amount of ammonium aluminum sulfate (also called ammonium alum or just alum) is added to the test tube.  The alum bonds to any organic matter in the soil.  Then the test tube is filled with water and capped.  The students then vigorously shake the test tube for about 30 second to a minute before placing it in a rack for 15 to 20 minutes.  During this time the soil that was mixed with the water settles.  The larger (heavier) particles sink faster than the smaller (lighter) particles.  This means that the soil will settle into distinct layers based on size.  The bottom layer will consist of sand particles of varying sizes.  This will be topped by a layer of silt.  Finally, if we allow the sample to sit long enough a layer of clay particles will settle on top of the silt - the clay usually is still suspended in the water after 20 minutes and may take as long as 24 hours to fully settle out.  Any small particles of organic matter in the soil will float to the top of the test tube - the alum bonds to the organic matter and helps it float.

The second experiment that the students perform involves sorting soil particles with the use of a sieve.  The sieve that we use has a series of 4 mesh screens of decreasing diameter.  These screens allow the students to separate the soil into five different parts by size.  The first screen removes any large particles from the soil (pebbles/gravel/etc.).  The next three screens sort out sand particle of varying sizes - coarse, medium, and fine.  The soil that remains at the bottom of the sieve is a combination of  silt and clay (and possible some very fine sand particles).  The sand particles all have that familiar "gritty" texture that can be felt between your fingertips.  The combination of silt and clay, when just touched has a fluffy texture like flour, but if you take a small amount between your finger and thumb it will feel "slippery" when rubbed together.

So what do these particles look like?  When magnified the difference in size is quite astounding. 

First up is the coarse sand.  These particles are quite large.  The first image shows the coarse sand with only front lighting.  The sand is composed of particles of several different minerals of varying colors.

Coarse Sand - 2X magnification

The second image shows the same particles with back-lighting.  The particles are large enough that most of them are opaque - meaning you cannot see light shining through them.

Coarse Sand with back-lighting - 2X magification

The next two images are of a medium grain sand. These particles are about 1/4 to 1/2 the size of the coarse sand.  The first image shows the sand with front-lighting only.  Again the sand is composed of several different mineral types.  The second image shows the same sample with back-lighting.  In this image, most of the grains are small enough that they are now translucent - meaning light shows through them.  Another difference from the coarse sand is that while the coarse sand was quite angular, most of the edges on the medium grain sand have been rounded off.

Medium Grain Sand - 2X magnification

Medium Grain Sand with back-lighting - 2X magnification

The next two images are of a fine grain sand.  The grains here are about 1/4 to 1/2 the size for the medium grain sand and about 1/16 to 1/8 the size for the coarse sand.  Again the different minerals can be differentiated based on color.

Fine Grain Sand - 2X magnification

At this size, all but the darkest particles are translucent when back-lit.

Fine Grain Sand with back-lighting - 2X magnification

The final two images show a combination of silt and clay.  There are also a few very-fine grain sand particles in this sample (the largest particles).  The clay is best seen in the second image as very small black dots against the back-lighting.

Very-fine Sand, Silt and Clay - 2X magnification

 

Very-fine Sand, Silt and Clay with back-lighting - 2X magnification.  The clay appears as very small black dots in this image.

As you can see from these image (all taken at the same level of magnification) there is a great degree of difference in the size of soil particle from the largest to the smallest.  One way to think about this size difference is this:  Imagine if a particle of sand were the size of a basketball; at this scale a particle of silt would be the size of a softball; and a particle of clay would only be about the size of a golf ball.

UPDATE (12MAY 2015):

I recently did a follow-up to this post showing the results of the soil sedimentation experiment detailed above.  Check it out here.

Program reminders for June 24th - 27th

If you are in the Mid-Michigan area there are several upcoming programs that might be of interest to you next week (24 - 27 JUN 2013).

First, as part of the Chippewa River District Library System Summer Reading Program, I am doing a series of programs at the five District libraries across Isabella County.  The theme of this year's Summer Reading Program is "Dig Into Reading".  My program is called "Dirt...Dig It!"  The first two presentations have already been completed.  The schedule for the remaining programs is as follows:

Veterans Memorial Library in Mt. Pleasant - Monday June 24th
Shepherd Community Library in Shepherd - Tuesday June 25th
Rolland Township Library in Blanchard - Thursday June 27th

All of these events are open to the public and are appropriate for all ages.  All events run from 4:00PM to 5:00PM.

Second, on Wednesday June 26th I will be working with staff and volunteers from the Mt. Pleasant Discovery Museum to install  a Native Pollinator Garden in front of the Museum.  We will be planting a variety of Michigan native plants that are adapted for a full-sun prairie environment.  Most of these plants were left over from a previous project.  Other plants are ones that self-seeded in one of the gardens that we had previously established.  If you are in the area and available to help, bring a garden trowel and show up at the museum to help plant.  We are starting at 5:30PM and going until the garden is completely planted.

The final activity for the week is with the Chippewa Watershed Conservancy at its Hall's Lake preserve.  The CWC hosts its 4th Thursday Program at Hall's Lake every month throughout the Spring - Fall.  The activity for June is centered around aquatic invertebrates.  I will be co-leading this program with retired Central Michigan University professor Doug Valek.  This program is geared toward families with children.  The CWC does ask that participants reserve a space ahead of time by calling 989-644-5045 or emailing at info@chippewawatershedconservancy.org.