Module 1: Trees

Topics addressed in this module include: introducing general tree anatomy and functions, identifying key characteristics of healthy and sick trembling aspen, understanding the nutrient and water cycles of trembling aspen, and understanding the various threats to, and their impacts on, trembling aspen.

Updated Nov. 4, 2019

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Table of Contents

Section 1.1: ...... 3 What Makes up a Tree? ...... 4 What Makes up Tree Roots on the Cellular Level? ...... 5 How do Trees Drink and Gather Nutrients? ...... 6 What are the Main Parts of a Tree Trunk? ...... 6 What Makes up a Tree Trunk on the Cellular Level? ...... 7 How do Trees Grow? ...... 8 How do Tree Rings Form? ...... 8 What Makes up a Tree Leaf on the Cellular Level? ...... 8 What is Transpiration and Capillary Action? ...... 10 Section 1.2: Trembling Aspen 101...... 11 Trembling Aspen ...... 13 Other Poplar Species ...... 13 How to Say “Aspen” in Various Indigenous Languages ...... 14 How to Identify Trembling Aspen ...... 15 How do Trembling Aspen Reproduce? ...... 16 Where do Trembling Aspen Grow? ...... 17 Additional Information about Clonal Aspen Stands ...... 18 Section 1.3: Aspen Health ...... 29 Do Trees Get Sick? ...... 30 Signs & Symptoms of Unhealthy Trees ...... 30 What Threatens a Trembling Aspen? ...... 31 The Most Common Trembling Aspen Threat...... 32 Section 1.4: The Water Cycle ...... 35 What is the Water Cycle? ...... 36 Water Cycle Processes ...... 37 Section 1.5: The Nutrient Cycle ...... 39 What is the Nutrient Cycle? ...... 40 Nutrient Cycle Process ...... 40 What Elements are Found in the Nutrient Cycle? ...... 41 What Factors Influence the Nutrient Cycle?...... 41 What Disturbs the Nutrient Cycle? ...... 42 Glossary ...... 43

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Section 1.1: Tree Anatomy & Functions

Image by cristi21tgv

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Section Overview

Outcomes Students will:

• Identify and describe the main parts of a tree (roots, trunk, and canopy). • Analyze the characteristics of cells in tree roots, trunk, and leaves. • Understand the structural and functional relationships among cells and tissues, including how cells and tissues contribute to the growth and health of the tree. • Comprehend how tree rings form annually, including how the size of each tree ring differs due to environmental conditions.

Key Terms

Adhesion Exodermis Parenchyma Cells Transpiration Capillary Action Heartwood Pericycle Tree Ring Chlorophyll Inner Bark Phloem Vascular Bundle Cohesion Late Wood Photosynthesis Vascular Cambium Early Wood Mesophyll Pith Layer Endodermis Outer Bark Sapwood Vascular Tissue Epidermis Osmosis Stoma Xylem

What Makes up a Tree? Trees are the largest plants on the planet. They provide us with oxygen, help stabilize the soil, and give life to the world’s wildlife. Trees are key members of the ecosystem and they are an excellent source of information about the environment. Through the TREE Program, you will get to investigate and find out what stories’ trees have to share, specifically looking at trembling aspen trees. For now, we start by looking at what trees are composed of. They can be divided into three main parts: the roots, the trunk, and the canopy.

• Roots Refers to all the tree parts below ground although roots can occasionally be above ground. Roots spread throughout the ground to anchor the tree in place and to gather water and nutrients. Roots also serve to store food for the tree throughout the winter. With some species, trees reproduce through their roots, creating what are known as clone trees. • Trunk Refers to the large column(s) of wood above ground but below the canopy. The trunk supports and elevates the canopy, as well as transports water and nutrients throughout the tree. • Canopy Refers to the leaves and branches of the tree. The canopy positions the leaves in full view of the sun, allowing for photosynthesis, transpiration, and hormone production in the tree.

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What Makes up Tree Roots on the Cellular Level? Tree roots are not only the anchor for the tree but essential in providing the tree with life. They soak up the necessary nutrients and water from the soil, feeding the growth cycle of the tree. Tree roots are composed of a complex and intertwined network of cells with two main types of structures: root hairs and lateral roots. Root hairs are a small outgrowth stemming off the lateral roots. Root hairs are continually being created and typically last 2-3 weeks before they die off and their nutrients are taken up by the roots. Root hairs provide a lot of surface area to absorb water and nutrients into the root. Lateral roots are the other main root structure and are much bigger than the root hairs. The lateral roots contain larger amounts of tissue, called vascular tissue, to transport nutrients and water throughout the tree. When roots are cross sectioned, we can see that they have five main types of cells: the epidermis, the exodermis, the cortex, the endodermis, and the vascular tissue (as shown in the figure below). The term tissue in this context refers to when cells are bundled together.

Figure 1 shows a cross-section of the cellular structure of roots. Image by CNX OpenStax.

Types of Tree Root Tissue • Epidermis The epidermis is the outermost tissue that is a physical barrier providing protection, insulation, as well as moisture and gas control. The epidermis also absorbs some nutrients and water. As the epidermis wears away and dies off, it is continually replaced by cells from the exodermis. • Exodermis The exodermis tissue is right underneath the epidermis and it replaces epidermis tissue as it wears away and dies off. This is very similar to how the inner bark replenishes the outer bark on the trunk which is explained in upcoming sections.

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• Cortex The cortex is a layer of cells that lies directly below the exodermis. The cortex transfers nutrients from the root hairs to the vascular tissue and is used for energy storage. The cortex separates the exodermis from the endodermis. • Endodermis The endodermis is the innermost layer of the cells with thicker cell walls. Some of these cells are coated in a water-repellent substance called suberin, which helps keep the endodermis watertight. The endodermis serves to regulate water and nutrient movement between the soil and the vascular tissue. • Pericycle The pericycle is composed of tissue that lies just inside the endodermis. The pericycle serves as internal support and protection for the root and it also forms new lateral roots by dividing rapidly in a specific location. • Vascular Tissue Vascular tissue is a bundle of cells that transport water and nutrients from the roots to the rest of the tree.

How do Trees Drink and Gather Nutrients? Trees drink by increasing the concentration of salts in their roots such that their roots have a higher salt concentration than the surrounding soil. When this happens, water flows into the roots to cause the root’s salt concentration to be in equilibrium (be the same) with the soil’s salt concentration. This process is known as osmosis. As the tree drinks, any minerals and nutrients that are dissolved in the water will flow into the roots as well. The roots separate these nutrients and minerals through cells called sieve cells and the nutrients and minerals then make their way up to the trunk to start feeding the rest of the plant.

What are the Main Parts of a Tree Trunk? Much like the variety of shapes and sizes seen with humans, tree trunks vary from one species to the next. However, there are parts that are common to all trees and these are the bark, the vascular cambium layer, the sapwood, the heartwood, and the pith (as shown in Figure 2).

The bark of a tree serves as a physical barrier for protection, insulation, and moisture control. Bark is separated into outer and inner bark. o Outer bark is composed of dead cells, commonly referred to as cork. Outer bark is covered with fine oxygen-breathing pores called lenticels. Figure 2 shows the anatomy of a tree trunk. Original image o Inner bark is composed of cells that transport by Thomas Steiner. sap and nutrients throughout the tree. As these cells age, they become outer bark.

The vascular cambium layer is a thin layer of cells with no specific task yet. This is where majority of the tree’s outward growth occurs. These cells continually divide with a varying rate throughout the year, creating phloem cells on the bark side and xylem cells on the inside. o Phloem cells transport sap and other nutrients throughout the tree. These cells become phellem cells as they mature and die off. o Xylem cells transport water and minerals throughout the tree. These cells become the sapwood as they mature and die off.

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Sapwood is composed of the xylem cells created by the layer surrounding it, the vascular cambium layer. Sapwood is responsible for water transport and storage through the tree’s daily water cycle. As these cells mature and die off, they harden and become more rot resistant, turning into heartwood.

Heartwood is a layer of wood composed of dead xylem cells and fiber bundles. Heartwood has a darker appearance than sapwood. Over time, the cells harden and become stronger, enabling the heartwood to be structural support for the tree.

The pith is the centermost portion of the tree and is composed of soft spongy parenchyma cells (explained below). The pith is surrounded by a ring of xylem cells, which is then surrounded by a ring of phloem cells. This allows the pith to store and transport water and nutrients throughout the tree.

What Makes up a Tree Trunk on the Cellular Level? As noted in the previous section, there are many different parts that make of a tree trunk. Within each of these parts, there are many different and uniquely specialized cells. The four main cells are xylem, phloem, parenchyma, and fiber bundles.

• Xylem Cells These cells are responsible for transporting water and minerals up from the roots throughout the tree. These cells combine together to form hollow tubes called vessel elements. It is important to note that xylem cells only transport water up (see Figure 3).

• Phloem Cells These trunk cells are responsible for transporting sap, which contains sugars and other nutrients, up and down throughout the tree. Phloem cells combine together to form hollow tubes called sieve tubes. These tubes are separated into smaller sections by sieve plates which allow for the bidirectional flow of nutrients. It is important to note that the phloem can transport nutrients up and Figure 3 shows the inner workings of xylem and phloem. Image by KI3580. down (see Figure 3).

• Parenchyma Cells Parenchyma cells provide support and nutrients to phloem and xylem cells and make up the bulk of plant cells.

• Fiber Bundles Fibers are long, slender cells that typically occur in bundles. These cells are mostly composed of cellulose, a tough material that makes up the cells walls and provides cell with structural support.

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How do Trees Grow? Trees expand and increase their size through the vascular cambium layer in their trunk. This layer continually divides at different rates throughout the year into phloem and xylem cells. The xylem cells are created on the inside of the tree and they are responsible for sapwood and heartwood growth. The phloem cells are created on the bark side of the tree and will quickly convert itself into the cork-like wood that we commonly associate as bark.

How do Tree Rings Form? Tree rings form every year as the tree is living and growing. These rings will be different sizes depending on the factors experienced during the growing season. These factors include: temperature, pests, diseases, access to water, nutrients, sunlight, and more. When the conditions are just right for the tree, the vascular cambium layer (refer back to Figure 2) will rapidly divide and create sapwood and bark at a set rate. This initial rapid growth creates lightly coloured, less dense wood called early wood. However, depending on the trees’ environmental conditions, the growth rate of the rings could change. As the season progresses towards winter, trees spend less energy on growth and more energy creating an energy store for the winter. This later slow growth creates the darkly coloured, more dense wood called late wood. As winter occurs, a tree experiences little to no growth but once spring comes around, the ring formation cycle repeats. This cycle is what gives trees the alternating light and dark circular patterns and are what we call tree rings (see Figure below).

early wood

Figure 4 shows a cross section of a tree trunk, labelled with certain parts of the tree ring.

What Makes up a Tree Leaf on the Cellular Level? The last main part of a tree are the leaves, which make up the canopy. As the roots are important for soaking in water and nutrients, leaves are important for soaking in sunlight, the other essential ingredient in giving plants life. In order to trap the sunlight and convert it so the tree can use it, tree leaves are composed of many specialized cells. The four main types of cells found in a leaf are the epidermis cells, mesophyll cells, stomata, and vascular bundles. These cells aid in photosynthesis, hormone production, and help move water to the outside of the leaf to be evaporated.

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• Epidermis The epidermis is the outer layer of cells that provides a physical barrier for protection and insulation for the leaf. The epidermis acts like a skin and is coated in a wax-like substance called cuticle, that helps prevent unwanted water loss. See Figure 5 for a visual representation.

• Mesophyll These cells are composed of parenchyma cells in long tube-like arrangements. Mesophyll is split in two layers, the palisade mesophyll and the spongy mesophyll, and these cells make up the middle section of a leaf (see Figure 5). o Palisade Mesophyll Palisade mesophyll is composed of tightly packed parenchyma tissue that contain large amounts of chloroplasts. Chloroplasts are small organelles filled with the photosynthetic pigment chlorophyll. Chlorophyll is responsible for photosynthesis, where energy from sunlight is converted to sugars. Since the chloroplasts need sunlight, the palisade mesophyll occupies the top inside portion of the leaves. o Spongy Mesophyll Spongy mesophyll is composed of loosely packed parenchyma tissue and occupies the bottom inside portion of the leaves. By packing the spongy mesophyll loosely, gases have plenty of room to move between the chloroplasts and the stomata allowing the chloroplasts access to fresh carbon dioxide.

• Stoma As shown in Figure 5, stoma are little natural openings in the epidermis that allow for regulated gas exchange between the tree and the atmosphere. Specialized cells, called guard cells, open and close the stomata (a collection of stoma) when the leaf needs more carbon dioxide or when the tree needs to transpire.

• Vascular Bundle A vascular bundle is a bundle of xylem and phloem cells that are essentially the veins and arteries of the leaves. Vascular bundles supply nutrients and water to the leaves for photosynthesis and transpiration. They also transport the sugars of photosynthesis to the rest of the tree.

Figure 5 shows the cellular structure of leaves. Image by Maksim.

Trees breathe by opening the guard cells around the stomata on the underside of their leaves. With the stoma open, gases from within the leaves can exchange with the air outside through diffusion until the gas concentrations have reached equilibrium or a balance.

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What is Transpiration and Capillary Action? Transpiration is the evaporation of water out of a tree. When the tree transpires, water is moved from the roots and up the stem using the properties of water cohesion and adhesion. With cohesion, water molecules are being attracted to themselves. With adhesion, water molecules are being attracted to other surfaces. As one water molecule lifts itself up slightly to adhere to the inside of a small tube, or in a plant’s case, the stem and leaves, water molecules below lift themselves up to cohere to the initial water molecule. This process is referred to as capillary action and for a model of this process, see Figure 6.

Figure 6 shows capillary action in action. The water

inside the tube has lifted itself higher than the water outside the tube. Capillary action is why test tubes have a meniscus line. Image by CNX OpenStax.

Additional Resources Anatomy and Biology of a Tree Leaf: https://www.thoughtco.com/anatomy-and-biology-of-tree-leaves-1343507 A webpage that covers the cellular structure of a tree leaf and how to use certain leaf structures to help identify tree types.

Encyclopedia Britannica: In Depth Tree Anatomy, Characteristic, and Growth: https://www.britannica.com/plant/tree/Tree-structure-and-growth A website that covers everything related to trees: the classification, the importance of them, the structure and growth of trees, and much more!

Plant Leaves and Leaf Anatomy: https://www.thoughtco.com/plant-leaves-and-leaf-anatomy-373618 A webpage that covers over leaf anatomy in detail as well as looks at carnivorous leaves and organisms that imitate as leaves.

US Forest Service: Tree Anatomy: https://www.fs.fed.us/learn/trees/anatomy-of-tree A website that covers the anatomy of a tree with links to additional educational resources for kids, teachers, and parents.

References Everett, T. H., Weber, L., and Berlyn, G. P. (2019). Tree Plant. Retrieved from https://www.britannica.com/plant/tree/Tree-structure-and-growth The Royal Parks. (2019). Why are trees so important? Retrieved from https://www.royalparks.org.uk/parks/the- regents-park/things-to-see-and-do/gardens-and-landscapes/tree-map/why-trees-are-important U.S. Forest Service. (n.d.). Anatomy of a Tree. Retrieved from https://www.fs.fed.us/learn/trees/anatomy-of-tree

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Section 1.2: Trembling Aspen 101

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Section Overview

Outcomes Students will: • Identify and describe characteristics of a trembling aspen tree, including root, trunk, canopy, catkins, and buds. • Acknowledge where trembling aspen grow and create a visual representation of the trembling aspen habitat across North America. • Investigate the reproductive tendencies of trembling aspen, including the factors that

lead trembling aspen to populate in large numbers.

Indigenous Groups Referenced in this Section

Indigenous Name Traditional Territory or Homeland

Anishinaabeg (Ojibwe, Chippewa, or The Eastern Woodlands, the Great Lakes, and westward across the Saulteaux): Subarctic. ah-nish-ah-na-bay

Denesųłiné: de-nay-suh-lin The subarctic interior of present-day Alaska and northwestern Canada.

Innu (Montagnais) The eastern portion of what is now known as the Quebec-Labrador peninsula.

Kanien'kehá:ka (Mohawk): gan-yan- Southeastern parts of present-day Ontario and Northern New York geh-ha-ga State.

Michif (Métis) Extends across what is now Southeast Ontario, Manitoba, Saskatchewan, Alberta, Northeast British Columbia, and the southern part of the Northwest Territories.

Mi’kmaq (Micmac): mii-gê-maw The Atlantic provinces now referred to as Nova Scotia, Prince Edward Island, New Brunswick, the Gaspe Peninsula of Quebec, and the Northeastern region of Maine in the United States.

Nakoda (Assiniboine) Across the prairies of present-day Saskatchewan and Alberta.

Nehiyaw (Cree): nay-hee-ow Across the prairie provinces and parts of what is now Ontario and Quebec.

Niitsitapi (Blackfoot): neet-sih-ta-pī Parts of what is now southern Alberta, Saskatchewan, and northern Montana.

Secwepemc (Shuswap): suh-wep-muh South-central interior of what is now British Columbia.

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Key Terms Catkins Clones Dioecious Root Sprouting Coniferous Tree Deciduous Tree Germination Stands

Trembling Aspen Trembling aspen is the most widely distributed tree species native to North America, ranging from the tip of northern Canada through to the United States and into Mexico. The scientific name for North America’s trembling aspen is Populus tremuloides and they are a deciduous tree, meaning their leaves change colour and fall off in the autumn season. A single trembling aspen tree typically does not survive more than 150 years but it can live for more than 200 years and grow up to 20-25 m (65-80 ft). The diameter of the trunk is usually around 20 to 80 cm (8 inches to 2 feet 7 inches). The tallest trembling aspen recorded was 36.5 m (119 ft, 9 in) and 1.37 m (4 ft, 6 in) in diameter. Trembling aspen are called as such due to their leaves. When you closely inspect a trembling aspen leaf, you should be able to notice how narrow the stem of the leaf is. When the wind blows, these leaves can easily be influenced to move and as such, you hear the trembling sound and see the leaves quivering in the wind. Aside from the trembling aspen TREE Video: Identifying Aspen title, they are also identified by many other names (see the Learn how to identify trembling aspen table below). There is a closely related aspen species across from this TREE video: the sea known as Populus tremula, whom European peoples http://bit.ly/TREE_Identifying have also referred to as quaking aspen because of the leaves’ tendency to quake or tremble.

Trembling Aspen Names English name Trembling Aspen French name Peuplier faux-tremble Genus Populus Species Populus tremuloides Synonyms Quaking Aspen, Quivering Aspen, Shivering Plant, Wagging Tongue, Golden Aspen, Mountain Aspen, Quakies, American Aspen, Trembling Poplar Other Poplar Species The trembling aspen is not the only poplar species that can be found in Canada. Listed below are 5 other species that are related to Populus tremuloides. It is important to note that the common name, White Poplar, is sometimes used to refer to anyone of the species listed below. Someone on the east coast of Canada might identify one of these species of tree as white poplar while someone on the west coast or the prairies or up north will be referring to a completely different species when they use the name, white poplar. For this reason, the TREE program will avoid using this common name and use either trembling aspen, Populus tremuloides, or an Indigenous pronunciation when referring to the poplar tree this program focuses on. • Populus balsamifera: the balsam poplar Explore the Poplar/Populus Species • Populus deltoides: the eastern cootonwood or Learn more about the variety of species in necklace poplar the Populus family by clicking the link • Populus grandidentata: the large-tooth aspen or here: https://en.wikipedia.org/wiki/Populus white poplar • Populus nigra: the cottonwood poplar, commonly referred to as black poplar • Populus trichocarpa: the black bootonwood or western balsam-poplar

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How to Say “Aspen” in Various Indigenous Languages There are approximately 70 - 90 Indigenous languages spoken across what is now Canada. Each Indigenous language is a part of a distinct language family. The umbrella term for a language family, such as Algonquian, has a group of languages that derive from it. For example, Néhiyawéwin (Cree) and Innu (Montagnais) are two languages that are a part of the Algonquian language family. Languages that are related via the same language family may exhibit similarities in Can you spot the similarities on the names they use for nouns like aspen. Listed in the chart how to say “aspen” between the below are ten ways to say “Aspen”* in ten Indigenous languages various Indigenous languages? across what is now known as Canada**.

Indigenous Language Language Family How to say “Aspen”

Denesųłiné Athabaskan k’es

Kanien'kehá:ka (Mohawk) Iroquoian Tsoskwe’ió:wane “Tree”: karònta

Michif (Métis) Half-Algonquian, Half- Li Traamb (lee tram) Indo European

Mi’kmaq (Micmac) Algonquian miti (mi·di)

Innu (Montagnais) Algonquian mitush (press link and then type “aspen”)

Nakoda (Assiniboine) Siouan waħtĩja čã čé-pta

Néhiyawéwin (Cree) Algonquian wāpimītos (wah·pē·me·tus)

Niitsitapi (Blackfoot) Algonquian A’kíítoyi

Ojibwemowin Algonquian Azaati / Azaadi (Anishinaabe)

Secwepemctsin (Shuswap) Salish Meltállp

*Where possible, the word is hyperlinked to an audio recording of a language speaker saying “aspen” in that language. In other cases, the pronunciation is listed in parentheses. If no pronunciation could be found, the word stands alone. **The ten languages included above are based on availability of resources (time and accessibility to information). In future editions of TREE, the aim is to expand this list to include more Indigenous languages. Please forward any websites or informative resources regarding Indigenous languages to [email protected].

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How to Identify Trembling Aspen Trembling aspen are characterized by a large variety of traits found in their canopies, trunks, roots, growing habits, and seasonal changes. It is important to note that they have a close- looking relative, the black poplar or Populus nigra, and it can be easy to mix up the two. Distinguishing characteristics of black poplar trees are that their bark is most often dark brown but can appear black and is thick. Sometimes it fades to white, the higher the tree grows. As well, black poplar leaves are similar to white poplar but have more of a spade shape and are usually larger. See Figure 7 for an image of a black poplar tree. The following lists describe characteristics of parts of the white Figure 7 shows a black poplar. Notice the difference in the bark poplar tree, which is the tree this program will focus on. from this image to the one below. Image by harum.koh.

Root

Trembling aspen roots are characterized as having: TREE Student Field Book • A shallow growing depth. Information in this section will help • A wide growth, up to 3 times wider than the students fill out the Student Field trees height. Book when collecting your samples. • A common root system among clones (explained in sections to follow).

Trunk Trembling aspen trunks are characterized as having: • A long and smooth cylindrical base with little tapering (becoming narrower towards the end). • Little to no branches in the lower section closest to the ground. • Bark that appears smooth and waxy with a pale green to white colour (see Figure 8). • Dark horizontal lines that furrow (creates a groove) with age. • A diameter up to 40 centimeters wide. Figure 8 shows a stand of trembling aspen, with their distinct Canopy white bark. Image by Zion National Park. Trembling aspen canopies are characterized as having: • A short-rounded shape. • A height up to 25 meters above ground. • Leaves roughly 3 to 7 centimeters long that are smoothly triangular in shape (heart-shaped), with a narrowed stem longer than the leaf (Figure 9). • Leaves that appear deep green from above, pale green from below, and turn yellow and occasionally red in autumn (Figure 10). • Leaves that tremble in the slightest breeze, giving the name trembling aspen. Figure 9 shows trembling aspen leaves. Image by James St. John.

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Catkins Trembling aspen are dioecious, meaning they have male and female reproductive organ, called catkins, on separate trees (see Figure 11). Catkins are characterized as having: • A cylindrical shape and a fuzzy appearance. • A length of 2 to 3 centimeters for males and 4 to 10 centimeters for females. • Tufts of hair covering thousands of seeds.

Figure 11 shows a catkin covered in hairy Figure 10 shows a trembling aspen canopy in the autumn. seeds. Image by Kaz. Image by Fairsing.

Buds Trembling aspen grow their leaves and catkins from a bud (Figure 12). Buds are characterized as having: • A dark reddish-brown colour, with 6 to 7 shiny scales covered in resin. • A conical, pointed shape where the tips of the scales point inward. • A typical length of 6 to 7 millimeters, with catkin buds being longer than leaf buds. Figure 12 shows the distinct dark red buds of a trembling aspen. Image by Matt Lavin. How do Trembling Aspen Reproduce? Trembling aspen reproduce through seeds or through root sprouting. Seeds Seeds develop on flowers called catkins (refer back to Figure 11) and the wind takes them to find the opposite reproductive organ. Reproduction through seeds produces trees with unique genetic makeup but is the least successful method due to the following reasons: o Pollen from male catkins must use the wind to find and fertilize female catkins. o Seeds from the fertilized female catkins use the wind to find soil with just the right conditions (water, elements, sunlight, etc.) to allow for germination (the growth of a plant from a seed). o Seeds lack protection or stored nutrients, so they are viable for a very short time.

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Root Sprouting The most common and successful way for trembling aspen to reproduce is by root sprouting. In this process, new aspen trees sprout from the roots of a mature aspen tree. These trees have a shared root system, which enables a process called root sprouting. Root sprouting produces numerous trees or clones with identical genetic information, leading to a colony of trembling aspen. Colonies can consist of a few to hundreds of identical trees. Where do Trembling Aspen Grow? Trembling aspen grow all across North America (see Figure 13). They are characterized as growing in a shade-less clearing, in sandy or gravelly soil that is rich in calcium, and in moist soils except in the wettest of soil sites. They are also an aggressive pioneer species, meaning they are the first tree species to colonize areas disturbed by fires, landslides, insect outbreaks, logging, and mining. For example, in the Central Rocky Mountains, the extensive groups of aspen are usually attributed to repeated wildfires. They may dominate a site until replaced by less fire-enduring but more shade-tolerant coniferous tree, which are trees that have needles instead of leaves (such as pine trees).

Figure 13 shows the habitat of trembling aspen across North America, as shaded in (Green).

Image by U.S. Geological Survey.

What is a Stand? In forestry, stands are areas within the forest that have been measured, mapped, outlined, and described as a distinct group of trees. Stands can be large or small, ranging from a few acres to hundreds. Trees within a stand will share similar characteristics such as age, size, condition, and species. Often, stands are defined by species dominance. For example, in an area with an abundance of trembling aspen trees, this becomes known as a trembling aspen stand.

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A trembling aspen stand is what appears to be a group of individual trees, but are all connected via the same root system. Scientists have described trembling aspen stands as clones, or clonal stands, because of their reproductive tendency to sprout new stems from the same lateral roots, thus creating a shared root system with genetically identical trees (see Figure 15). Trembling aspen stands can grow as a single- species stand or in a mixed-species stand. As stands with a single species age, more shade tolerant species may grow within that stand. This occurrence produces a mixed species stand that can Figure 14 shows a mountainside covered in clonal colonies of include white spruce, black spruce, balsam fir, trembling aspen. Each clone stand is identifiable by the difference in white birch, balsam poplar, and jack pine. timing when turning to their autumn colours. Image by Beeblebox.

Additional Information about Clonal Aspen Stands An aspen clone is a single tree that sends out individual stems from its roots (see Figure 15). If left undisturbed, these stems eventually grow into aspen trees. While the trees themselves are individuals, the root system is the same, meaning the trees connected to the same root system have identical DNA. Although the average lifespan of a single aspen tree is 150 - 200 years old, a clone can survive for thousands of years because of its ability to sprout new stems from its roots. Aspen clones can cover a wide range of land from less than 1 acre to more than 100 acres. There can be a single clone in an area or there can be multiple (see Figure 14). When there are multiple clones in a single area, the stands are distinguished by various traits such as bark character, leaf shape and size, or resistance to disease. Autumn leaves offer the clearest indication of there being numerous clones in a single area. For instance, a clone may turn colour earlier or later or show a different fall colour than surrounding clones. In the spring, clones will produce leaves at different times and will pollinate at different times.

Figure 15 shows how a trembling aspen clone develops. Image by M. Grant & J. Mitton.

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The Pando Clone The Pando clone is the largest organism on earth and is located in Fishlake National Forest in southern Utah. In Latin, “pando” literally means “I spread.” Also known as “The Trembling Giant,” the Pando clone consists of 47,000 aspen trees spanning across roughly 100 acres. The total weight of the Pando clone is more than 13 million pounds! The general consensus on Pando’s age is 80,000 years old, though some scientists argue it is closer to 1 million years in age. The typical age of aspen clones ranges between 5 years to 10, 000 years old while a single aspen tree averages a lifespan of 150-200 years old.

Figure 16 shows a small portion of the massive organism that is Pando. Image by J Zapell.

What Makes Up an Aspen Lesson Identify trembling aspen characteristics and threats to this tree in this activity. Lessons can be downloaded and adapted from here: http://bit.ly/TREE_TeachingResources

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Additional Resources Case Study: The Glorious, Golden, and Gigantic Quaking Aspen: https://www.nature.com/scitable/knowledge/library/case-study-the-glorious-golden-and-gigantic-13261308 An online article that discusses the general characteristics of quaking aspen, the reproduction processes of these trees, and how clone species develop.

Government of BC: General Trembling Aspen: https://www.for.gov.bc.ca/hfd/library/documents/treebook/tremblingaspen.htm Website from the Government of BC that covers the general characteristics and uses of trembling aspen.

Natural Resources Canada: Trembling Aspen: https://tidcf.nrcan.gc.ca/en/trees/factsheet/58 Government of Canada website that covers general characteristics of trembling aspen, insects and diseases that impact these trees, and this website has a collection of aspen images.

US Department of Agriculture: How Aspen Grow: https://www.fs.fed.us/wildflowers/beauty/aspen/grow.shtml United States Department of Agriculture, Forest Service website on how aspen grow, how they reproduce, and why they have the name of quaking or trembling aspen.

References Government of British Columbia. (2019). Trembling aspen: Populus tremuloides. Retrieved from https://www.for.gov.bc.ca/hfd/library/documents/treebook/tremblingaspen.htm Native American Totems. (2012) Plant totem: Quaking aspen. Retrieved from http://native-american- totems.com/plant-and-mineral-totems/plant-totem-quaking-aspen/ Natural Resources Canada. (2015). Trembling aspen. Retrieved from https://tidcf.nrcan.gc.ca/en/trees/factsheet/58 U.S. Forest Service. (n.d.). How Aspen Grow. Retrieved from https://www.fs.fed.us/wildflowers/beauty/aspen/grow.shtml Wikipedia. (2019). Populus tremuloides. Retrieved from https://en.wikipedia.org/wiki/Populus_tremuloides

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What Makes Up an Aspen?

Time: 60 minutes Grade Level: 8 Concepts Covered: Parts of a trembling aspen, characteristics of trembling aspen, names of trembling aspen, common trembling aspen threats Materials Needed: Aspen Flashcards (multiple copies), Writing utensils, paper (chart paper, poster board, etc.), Consistent internet access (computers, iPads, smart phones, etc.; optional)

KEY QUESTIONS CURRICULUM OUTCOMES (General)

• How might trees be classified? • Identify trembling aspen characteristics • Why is it important to classify trees? from terminology, facts, and different • What is the classification of a trembling languages. aspen? • Identify threats to trees and explain • What are the parts of a tree? rationale of listed item being a threat. • Why are trees important to the ecosystem? • What are some of the practical uses of trees? How can human beings use trees?

INTRODUCTION (Motivational Set)

Assess students’ prior knowledge by creating a concept map on the board. Write “Trembling Aspen” in the middle and ask students to share what they know of these trees. What words do they associate with this tree? What information have they learned about these trees from the modules and lessons? When complete, inform students that they will be exploring their knowledge of trembling aspen through various inquiry activities while in groups.

TASKS

1. Set up three stations, one for trembling aspen flashcards, one for a puzzle of aspen, and one for a brainstorming station. 2. Divide students into three groups and have them start at a station. 3. For each station, the students will do the following: Station 1 – Aspen Trivia In groups, students will identify parts of an aspen by reading clues or viewing pictures on each flashcard. There will also be true or false questions, and language identification.

FOR EXAMPLE: • I have a smooth, waxy appearance • I am pale green to almost white in colour • I have horizontal lines that grow dark and furrowed with age Which part of an aspen am I? Answer: Bark

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Station 2 – Differences of Trees Students are to think about all the different trees they are familiar with and know of. If they have access to the internet and can find images of the trees, have them draw out the leaf or the whole tree rather than listing the names of the trees. Have them write how they are familiar with the tree. For example, if students write or draw a maple tree, they might be familiar with it because it is a symbol of Canada or they have maple trees growing in their yard. If students need help, a good place to look online is at the following website: https://treecanada.ca/resources/trees-of-canada/.

Station 3 – Threat Brainstorming Students will work together to create a list, a web, or concept of what they deem to be threats to the livelihood of trees. Have students also state why what they listed is considered a threat. If students are finding it difficult to come up with additional threats, ask them to reflect on the threats they have already listed and review their rationale for the threats. For example, if students agree a caterpillar is a potential threat to a tree, could another insect perhaps be a threat? What do caterpillars do?

CONCLUSION

Once students have completed each station, gather them back as a class. Ask students how the trivia went for them and if there were any points or questions that stuck out to them. What made these points interesting to them? Ask them to elaborate on their thoughts and share. Next, ask them about the puzzle and if they had any difficulty completing it. Would they be able to identify the white poplars from the black ones when they go collect samples? Finally, ask your students how they felt about the threat brainstorming activity. What threats were they able to identify? Explore their reasoning behind the threats. Information on the most common trembling aspen threats will be explored in Section 1.3.

SUGGESTIONS FOR ASSESSMENT

- Entry/exit slip - Journal reflection - Participation in discussions and/or station activities

LESSON EXTENSIONS

- Have students create their own flashcards and use with their peers. Or create a jeopardy-style trivia game to test out their knowledge! - For station two, have images of various types of trees and have students match up an image with the correct name (be sure to include images of white poplars and black poplars). - Take the threat brainstorming station and make it into a research report for students before you get to Section 1.3. Students could create a newspaper article of their report.

RESOURCES

- TREE Module 1

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- Online Jeopardy Game template: https://jeopardylabs.com/ - Trees of Canada website: https://treecanada.ca/resources/trees-of-canada/

ADDITIONAL NOTES

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Aspen Trivia! – Flashcards Activity Note: Print pages separately

What am I? What am I?

1. I have a smooth, waxy 1. I’m cylindrical and appearance. fuzzy, with hair that is

home to numerous tiny 2. I am pale green to almost seeds. white in colour. 2. I have male and female 3. I have horizontal lines reproductive organs that that grow dark and grow on separate trees. furrowed with age. 3. Without me, aspen could

not reproduce.

Answer: Bark Answer: Catkin Answer:

What am I? What am I?

1. I’m heart-shaped. 1. I’m dark-reddish brown in colour. 2. I am usually between 3 – 7 centimetres in length. 2. I’m conical and pointed, with my tips curving 3. I’m deep green on my inward. upper surface, and pale

green on my lower 3. For flowers, I’m larger.

surface. For leaves, I’m smaller.

Bud Answer:

Leaf Answer:

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What am I? What am I?

1. I am long and 1. I am short and rounded.

cylindrical. 2. I can be found at the top 2. I am branch-free below of the tree. my crown. 3. In summer, I’m full. In 3. I am smooth with little winter, I’m bare.

taper.

Crown Answer: Trunk Answer:

True or False True or False

Trembling aspen to be 50 Trembling aspen are defined metres (164 feet) in height, as an aggressive pioneer and up to 80 centimetres in species. diameter.

. fires frequent to

diameter. in centimetres

persist even when subjected subjected when even persist can and areas

25 metres (82 feet) in height, and up to 40 40 to up and height, in feet) (82 metres 25

burned burned

colonize readily to ability its proving

Answer: False. Trembling aspen grow up to to up grow aspen Trembling False. Answer: Answer: True. Aspen earned this title after after title this earned Aspen True. Answer:

True or False True or False

Trembling aspen are noted A clone does not turn colour for their ability to regenerate in the fall. As a deciduous using a method called “root tree, it simply loses its leaves sprouting.” as the weather turns cold.

structure. neighbouring aspen clones. aspen neighbouring

characteristics and share a root root a share and characteristics identical its than variations colour fall different exhibit

as clones. All the trees in a clone have have clone a in trees the All clones. as

and fall the in later or earlier colour turn may

genetically identical trees, often referred to referred often trees, identical genetically

clone A orange. or yellow as such colours

Answer: True. Root sprouting results in many many in results sprouting Root True. Answer: Answer: False. Aspen clones turn to autumn autumn to turn clones Aspen False. Answer:

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True or False True or False

Trembling aspen are the Trembling aspen refers to most widely distributed both white and black poplar native North American tree trees. species.

Mexico. into and States, United the through

aspen are found across Canada, Canada, across found are aspen of Stands

vastly diverse regions and environments. environments. and regions diverse vastly

only refers to white poplar. poplar. white to refers only

Answer: True. Trembling aspen grow in in grow aspen Trembling True. Answer:

Answer: False. The name trembling aspen aspen trembling name The False. Answer:

True or False True or False

The branches of trembling Clonal stands live longer aspen can be boiled in water than individual trembling and used as a cleanser for aspen. guns, traps, and buckskins.

odour.

200 years old. years 200 - 150 of lifespan a

themselves in this solution to remove human human remove to solution this in themselves

years old while a single aspen tree averages averages tree aspen single a while old years

as a cleanser, and hunters can also wash wash also can hunters and cleanser, a as

000 10, to years 5 between ranges clones

Answer: True. Boiled branches in water work work water in branches Boiled True. Answer:

The typical age of aspen aspen of age typical The Answer: True. True. Answer:

wāpimītos Li Traamb (wah-pee-me-tus) (lee trahm) is the ______word for is the ______word for trembling aspen. trembling aspen.

world today. world

estimated 200 fluent speakers left in the the in left speakers fluent 200 estimated

Blackfoot. and Micmac, Ojibwe, on the list of endangered languages with an an with languages endangered of list the on

family, which also includes Saulteaux, Saulteaux, includes also which family,

is Michif language. syncretic a is it meaning

language of the larger Algonquian language language Algonquian larger the of language from a combination of Cree and French, French, and Cree of combination a from

-

Answer: Cree. The Cree language is a sub a is language Cree The Cree. Answer: derives language Michif The Michif. Answer:

TREE: Module 1: Trees Page 27

Azaati / Azaadi A’kíítoyi

is the ______word for is the ______word for trembling aspen. trembling aspen.

2015). Dictonary, s ’ People

Montana. Northwestern and Alberta

Montana in the United States (Ojibwe (Ojibwe States United the in Montana

thousands of years in what is now known as as known now is what in years of thousands

Manitoba in Canada, and from Michigan to to Michigan from and Canada, in Manitoba

languages and has been spoken for for spoken been has and languages

Anishinaabe people from Ontario to to Ontario from people Anishinaabe

one of the westernmost Algonquian Algonquian westernmost the of one

Central Algonquian language spoken by the the by spoken language Algonquian Central Blackfoot. The Blackfoot language is is language Blackfoot The Blackfoot. Answer:

Answer: Ojibwe. The Ojibwe language is a a is language Ojibwe The Ojibwe. Answer:

ghi Peuplier faux-tremble (soft g: gee) is the ______word for is the ______word for trembling aspen. trembling aspen.

Alberta. Southern of plains

northwestern Canada, and extends into the the into extends and Canada, northwestern

speakers are the majority. majority. the are speakers

the subarctic interior of Alaska, Alaska, of interior subarctic the

Quebec is the only province where French French where province only the is Quebec

Athabascan language family and is spoken in in spoken is and family language Athabascan

s two official languages. In Canada, Canada, In languages. official two s ’ Canada language is a member of the larger larger the of member a is language

Canadian. French is one of of one is French Canadian. - Answer: French Answer: Answer: Denesuline. The Denesuline Denesuline The Denesuline. Answer:

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References for What Makes Up an Aspen Lesson

Alberta Education. (2010). Blackfoot language and culture twelve-year program kindergarten to grade 12. Retrieved from https://education.alberta.ca/media/563920/blackfoot-k-12.pdf The Canadian Encyclopedia. (n.d.) French language in Canada. Retrieved from https://www.thecanadianencyclopedia.ca/en/article/french-language/ Canadian Light Source Inc. (2018). The light source scavenger hunt. Retrieved from http://bit.ly/LiSSE_Hunt The Ojibwe People’s Dictionary. (2015). About the Ojibwe language. Retrieved from https://ojibwe.lib.umn.edu/about-ojibwe-language Saskatchewan Indian Cultural Centre. (n.d.) Dene history. Retrieved from http://www.sicc.sk.ca/dene_history.html

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Section 1.3: Aspen Health

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Section Overview

Outcomes Students will: • Analyze signs and symptoms of an unhealthy tree and compare its characteristics with a healthy tree. • Investigate and describe threats to a trembling aspen and evaluate the impact of each threat.

Key Terms Canker Discolouration Foul Smell Fungi Defoliation

Do Trees Get Sick? Much like with humans, trees and other plants can get diseases and/or be impacted by threats and become sick. Trees do have systems in place to combat diseases and threats but sometimes they are not successful and the tree dies. This process is part of nature and one all living things go through.

*A scientific study published by Canadian Forest Service Publications narrowed in on factors that affect trembling aspen health in the boreal forest of Alberta, Saskatchewan, and Manitoba. The article is the foundation of this section and can be found here: http://nofc.cfs.nrcan.gc.ca/bookstore_pdfs/22828.pdf

When it comes to sample trembling aspen for the TREE program (sampling process outlined in Module 4), it is important you do your best to identify a healthy tree from a sick one. Some sick trees will not show signs and symptoms on the outside but when you obtain your tree core, you will see that the parts of the core are starting to rot. If the sample you collect is unhealthy or rotting, we will be unable to collect any usable data for the TREE program. Signs & Symptoms of Unhealthy Trees There are numerous pests and diseases that affect trembling aspen. The following lists are some common things to look for when assessing the health of aspen in your area. Unhealthy bark will have at least one of the following symptoms: • Discoloration: Any colour other than a pale green/white. • Foul Smell: Wood rotting below the bark will have a foul smell. • Cankers: Discolored and depressed bark that is dead (see Figure 19). • Fungi: Any fungal bodies, like mushrooms or mold, visible around the trunk or higher in the bark is a clear sign that the tree is infested (see Figure 17). Figure 17 shows small brown fungi growing on an Aspen tree (seen at the center and left side of the tree).

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Unhealthy leaves will have at least one of the following symptoms: ● Discoloration: Any color other than green. The exception is in autumn when the leaves transition to their fall colours of mostly yellow and occasionally red. Discoloration of unhealthy leaves occur in tiny spots. These spots can grow and merge to cover the entire leaf (see Figure 18). ● Fungi: Any visible fungal bodies on the leave are a clear sign that the tree is infected. ● Defoliation: Lack of leaves during warmer seasons over small or large areas of the tree.

Figure 18 shows leaves from a trembling Aspen affected by Figure 19 shows a tree canker, causing slight discolouration Marssonina Leaf Spot. Image by Manfred Mielke. and anomalies. Image by AvalokiteshvaraBudha.

What Threatens a Trembling Aspen? The diagram below lists various threats to a trembling aspen. Aspen can be harmed by pests (P) or diseases (D). Falling trees, rubbing of neighbouring trees, or human impact (such as contact with a vehicle) can also cause mechanical damage, which make aspen more susceptible to pest invasion or disease.

Relatively Serious Less Serious

Forest tent caterpillar (P) Aspen leaf beetle (P)

Armillaria root disease (D) Aspen leafroller (P)

Large aspen tortrix (P) American aspen beetle (P)

Poplar peniophora (D) Poplar borer (P)

False tinder conk (D)

Hypoxylon canker (D)

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However, not every threat or disease impacts a trembling aspen strand. The presence of a specific pest is often dependent on specific stand conditions. For instance: ● Diseases such as the large aspen tortrix and poplar borer appear to prefer aspen stands with larger, more widely spaced trees. ● Armillaria root disease and hypoxylon canker are both found in the less dense stands, which means these pests may be thinning out trembling aspen. ● The poplar peniophora disease prefers younger, smaller, and more dense stands. ● False tinder conk is more prevalent in older, larger, less dense stands.

The Most Common Trembling Aspen Threat In the prairie provinces, the forest tent caterpillar (FTC; see Figure 20) causes the most harm to trembling aspen. An outbreak of FTC’s leads to a reduction in growth and tree mortality through defoliation. Sites affected by FTC defoliation show an increased proportion of weakened, declining, and dead aspen trees.

When an Aspen Gets Sick Lesson Identify the signs and symptoms of healthy and unhealthy trees and investigate the different threats and diseases that impact them. Lessons can be downloaded and adapted from here: Figure 20 shows a forest tent caterpillar. Image http://bit.ly/TREE_TeachingResources by Greg Hume.

Additional Resources Factors Affecting Trembling Aspen Health on the Prairies: http://nofc.cfs.nrcan.gc.ca/bookstore_pdfs/22828.pdf Online article from the Forest Ecology and Management Journal that discusses the results of a survey on the boreal forests of Alberta, Saskatchewan, and Manitoba on the various factors (such as forest tent caterpillars, root diseases, climate) impacting trembling aspen.

Natural Resources Canada: Trembling Aspen: https://tidcf.nrcan.gc.ca/en/trees/factsheet/58 If you click on the insects and diseases tab on the webpage, you can get more details into the various insects and diseases that impact trembling aspen. There is a tab as well for the general description of this type of tree.

References Brandt, J.P., Cerezke, H.F., Mallett, K.I., Volney, W.J.A., and Weber, J.D. (2003). Factors affecting trembling aspen (populus tremuloides michx.) health in the boreal forest of Alberta, Saskatchewan, and Manitoba, Canada [Webpage Publication]. Retrieved from https://cfs.nrcan.gc.ca/publications?id=22828

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When an Aspen Gets Sick

Time: 5 hours Grade Level: 8 Concepts Covered: Signs & symptoms of sickness, trembling aspen threats and diseases, scientific inquiry, reliable sources, team work Materials Needed: Consistent internet access (computers, iPads, smart phones, etc.), writing utensils, notebook

KEY QUESTIONS CURRICULUM OUTCOMES (General)

• What does a healthy trembling aspen • Identifying signs and symptoms of look like? healthy and unhealthy trembling aspen. • What are the signs and symptoms of an • Investigate the impact threats and/or unhealthy trembling aspen? diseases have on trembling aspen. • What kinds of insects and disease • Employ the process of scientific inquiry negatively affect the health of trembling through group work. aspen? • Present research findings through either • Which insects and disease have affected visual and/or oratory presentation. trembling aspen in your region?

INTRODUCTION (Motivational Set)

Ask students what happens when you get sick? Write the word sick in the middle of the board and create a list, web, or concept map of all the ideas students associate with being sick. Encourage students to think about how you look when you are sick and how they feel. Mention to students that in this activity, they will be looking at how trees get sick and what the various signs and symptoms of unhealthy trees are.

TASKS

1. Ask students why trees get sick? What would make trees sick? 2. Refer back to the concept map and ask students to apply these same ideas to trees. How would trees look sick? Feel sick? Ask students to create a list, web, or concept map of signs and symptoms of ill trees. Do students know of any tree illnesses threatening our forests? What illness? How do you know? 3. Let students work for a bit and after a certain time period, have students share their answers and discuss their findings. 4. Next, organize students into groups and inform them that they will work collaboratively to research potential threats to trembling aspen health. Students will choose one insect or disease and formally organize their information in their desired medium. Students may create a poster, a PowerPoint, an audio file, a video, etc. Use the following question to guide students’ inquiry: o Key inquiry question: Has the insect or disease you chose to research impacted the trembling aspen in your community? How do you know? o If your group’s chosen insect or disease has not impacted the health of trembling aspen in your

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region, why not? 5. Teachers are encouraged to help students by providing a list of credible resources to aid in research. Students could use other resources with teacher confirmation. Students will seek to verify this information by engaging in online research and contacting community members 6. Be sure to also talk to students about sourcing information (perhaps require them to provide a works cited list).

CONCLUSION

Upon completion, each research team will present their information to the class. Audience members will be encouraged to take notes, ask questions, and provide feedback on the research. Once everyone has finished presenting, all final products are to be displayed around the classroom.

SUGGESTIONS FOR ASSESSMENT

- Use a rubric to assess the students’ report and/or presentation. You could include assessment factors such as content of research, appropriate sourcing, visual presentation, organization, oratory presentation (loudness, clarity, tone, etc.), and many more. - Or use a checklist to see if students have completed everything in their inquiry. Be sure to communicate and share this checklist at the start of their process. - Have students complete personal reflections on what they learned during the process and how they would expand on this knowledge and/or apply it. Assess these reflections. - Have students complete reflections on each other and themselves to look at how each member contributed to the team.

LESSON EXTENSIONS

- Require students to complete both a visual presentation and written report. - Ask students to create a poster board or scientific poster of their findings. - Have students interview experts and community members to inquire further into the issue they are studying.

RESOURCES

- TREE Module 1 - Rubistar website (create fast and easy rubrics): http://rubistar.4teachers.org/index.php

ADDITIONAL NOTES

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Section 1.4: The Water Cycle

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Section Overview

Outcomes Students will: • Investigate the water cycle as a representation of energy flow and the cycling of matter through ecosystems. • Examine a visual model of the water cycle to illustrate how water moves through ecosystems. • Conduct an experiment that displays evidence of water vapors releasing into the

atmosphere.

Key Terms

Condensation Infiltration Run-off Transpiration Evaporation Precipitation

What is the Water Cycle? The water cycle is a series of processes by which water evaporates from the surface of the earth, rises into the atmosphere and cools, condensing into water droplets held by clouds, and then is released to the earth’s surface as precipitation (rain, hail, sleet, or snow) before the process starts again (see Figure 21).

The water cycle is important to a tree as water is an essential ingredient to the process of photosynthesis. Water also helps move nutrients through various systems and are absorbed by the trees. Some of these nutrients help aid in the growth of trees through various systems; others can be detrimental to the growth. With that in mind, when it comes to analyzing your tree cores and soil at the Canadian Light Source (CLS) and the Mistik Askiwin Dendrochronology (MAD) Lab (see Module 5 for more information), certain elements of interest may show to be present in your sample. You may wonder why these elements are in your sample and how they got there. By understanding the water cycle, you should have a sense of how elements can move through the water cycle from various water bodies.

Interactive Water Cycle Diagrams

Beginner: https://water.usgs.gov/edu/watercycle-kids-beg.html Intermediate: https://water.usgs.gov/edu/watercycle-kids-int.html Advanced: https://water.usgs.gov/edu/watercycle-kids-adv.html

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Water Cycle Processes

Figure 21 shows the water cycle processes. Image by NASA.

1) Evaporation The sun is the driving force of the water cycle. When the sun heats up bodies of water such as oceans, rivers, lakes, puddles, etc., the water changes from liquid to gas in a process called evaporation. The water vapour rises high into the atmosphere.

2) Condensation As water vapor rises in the atmosphere, it cools off as it passes through air with colder and colder temperatures. As the water vapour cools, it changes from gas to liquid in a process called condensation. The condensing water vapour forms tiny water droplets that make up clouds.

3) Precipitation As more water condenses into water droplets, the clouds will continue to grow until they become saturated and too heavy. When this happens, the water droplets fall to the earth as rain, snow, or hail in a process called precipitation.

4) Run-Off The rain or melted snow on the ground flows back into various bodies of water such as rivers, lakes, streams, and oceans. The term for this water flow is called run-off. The water will then be evaporated again, starting the cycle all over.

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5) Infiltration Water that remains on the earth’s surface is soaked up by the soil using a process called infiltration. Trees absorb water from the soil and transport it to the leaves through the stem in a process known as plant uptake.

6) Transpiration During the plant uptake process, the water and nutrients found in the soil are soaked into the tree by the roots and move upward into the trunk, branches, and leaves for use in photosynthesis. Eventually, the water makes its way to the leaves and stem and evaporates in the process called transpiration (See Section 1.1 for transpiration and capillary action). Transpiration from trees and plants is closely related to the evaporation of water bodies. This leads us back to step one and the cycle continues.

Transpiration in Action Activity Since the transpiration process cannot be seen by the naked eye, a critical thinker may question the validity of the transpiration process. Follow these simple steps to conduct an experiment that displays evidence of water vapors releasing into the atmosphere:

1. Tie a clear plastic bag to the leaves of a classroom plant 2. Leave the bag alone for roughly an hour 3. Revisit the plant and witness water vapor droplets on the inside of the bag

Additional Resources Evapotranspiration and the Water Cycle: https://water.usgs.gov/edu/watercycleevapotranspiration.html Webpage by the United States Geological Survey (USGS) that explains what happens during plan transpiration and it looks at the different factors that impact these processes.

Forest Ecosystems: Nutrient Cycling: http://nofc.cfs.nrcan.gc.ca/bookstore_pdfs/26204.pdf An online article from the Encyclopedia of Soil Science journal that examines the nutrient cycle and the factors that impact these processes.

A Simple Guide to the Steps of the Water Cycle: https://sciencestruck.com/steps-of-water-cycle A webpage found in the Science Struck website that breaks down the steps of the water cycle with corresponding visuals.

The Water Cycle for Schools: Intermediate Ages: https://water.usgs.gov/edu/watercycle-kids-int.html A webpage also by the USGS that has a large graphic that outlines the process of the water cycle.

References Science Struck. (2019). A simple guide to the steps of the water cycle. Retrieved from https://sciencestruck.com/steps-of-water-cycle U.S. Geological Survey. (n.d.). Evapotranspiration and the water cycle. Retrieved from https://water.usgs.gov/edu/watercycleevapotranspiration.html

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Section 1.5:

The Nutrient Cycle

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Section Overview

Outcomes Students will: • Interpret the nutrient cycle as a representation of energy flow and the cycling of matter through ecosystems. • Recognize some of the elements trees require and use for growth and survival. • Understand the factors that influence the nutrient cycle, including climate, location, various forest ecosystems, and potential disturbances.

Key Terms Compounds Elements

What is the Nutrient Cycle? The nutrient cycle is the exchange of elements between living and nonliving things. It is nature’s recycling system. The nutrient cycle shows how essential nutrients travel through the environment, providing every organism what it needs to live. There are various nutrient cycles (ex: carbon, oxygen/water, nitrogen) but this section will provide an overview of the general process for essential nutrients. Nutrient Cycle Process Much like the water cycle, there is no beginning or end to the nutrient cycle process, but this process can be broken down step-by-step. • First water and air penetrate the soil cause nutrient-rich litter (leaves and other plant matter) breaks down into the soil, releasing nutrients and minerals. • The litter is then decomposed and broken down by organisms called decomposers (ex: fungi, algae, earthworms, millipedes, slugs, etc.). • The soil stores these nutrients and a certain percentage is absorbed by the tree, leading to plant growth and nutrient-rich leaves. • The nutrients also leave from the soil in gaseous form and enter into the atmosphere to then be absorbed by the leaves, restarting the cycle.

As shown in Figure 22, this cycle has been shown for one tree but can be expanded for entire forests. Figure 22 shows a tree participating in the nutrient cycle. Original image by Pixabay

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What Elements are Found in the Nutrient Cycle? Trees and plants need many nutrients in order to thrive. Nutrient availability is strongly influenced by the quantity and quality of litter produced in a forest. There are three elements critical for tree survival and these are carbon, nitrogen, and phosphorus. These elements are the building blocks of all matter but there are also many other elements and compounds that make up nutrients. Elements are the simplest substances found in the world and that make up all matter while compounds refers to something composed of two or more elements. The periodic table below shows the elements commonly found in the nutrient cycle.

Trees require large quantities of elements such as: Trees also use small quantities of elements such as: • Hydrogen (H) • Boron (B) • Carbon (C) • Chlorine (Cl) • Oxygen (O) • Manganese (Mn) • Nitrogen (N) • Iron (Fe) • Magnesium (Mg) • Copper (Cu) • Phosphorus (P) • Zinc (Zn) • Potassium (K) • Calcium (Ca)

Figure 23 highlights some of the important nutrients trees need on the periodic table. Original image by LeVanHan.

What Factors Influence the Nutrient Cycle? The nutrient cycle is controlled by the climate, location, and living communities in forest ecosystems. The role of each factor varies from the diversity of forest ecosystems around the world (boreal, temperate, tropical). Even in Canada, we see this diversity among our forest. Each of these forests behave uniquely and respond to environmental conditions differently, storing varying rates of carbon and producing different amounts of nutrient-litter. For example, in tropical forests, there is a low storage rate of carbon and a high amount of litter production while in boreal forests, there is high carbon storage and low litter production.

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What Disturbs the Nutrient Cycle? Fire, harvesting, storms, pests or disease can all affect the nutrient cycle processes. Often, these disturbances are natural and important to the forest ecosystem as some nutrients are added or lost which can have a positive or negative impact. For example, after a fire, there is a redistribution of nutrients in the forest due to the combination of the following: 1. Fire burns all live and decomposing plant material. 2. Ash is distributed by the wind. 3. Water erodes the surface soil. 4. Liquid filtering of nutrients through and out of the soil. The relative importance of these processes varies with each nutrient and is modified by differences in fire intensity, soil characteristics, landscape, climatic patterns, and biotic communities. It may help to remember the information from this module or refer back to it when you are conducting your data analysis on your tree and soil samples. If you notice a presence of a certain element, recall how nutrients are transported and stored and it may help you understand how the element found its way into the tree you sampled.

References Bhatti, J. & Foster, N. (2006) Forest ecosystems: Nutrient cycling. Encyclopedia of Soil Science, 718-721. doi: 10.1081/E-ESS-120001709 Wikipedia. (2019). Nutrient cycle. Retrieved from https://en.wikipedia.org/wiki/Nutrient_cycle

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Glossary

Adhesion - When a substance, such as water, is attracted to, or sticks to something else. Canker - Discolored and depressed bark that is dead. Capillary Action - The process where one water molecule lifts itself up slightly to adhere to the inside of a small tube, or in a plant’s case the stem and leaves, and the water molecules below lift themselves up to cohere to the initial water molecule. Catkins - A cylindrical and fuzzy collection of seeds that carry either the male or female reproduction organ for plants. Chlorophyll - A photosynthetic pigment that helps convert sunlight energy to chemical energy, like sugar. Clones - A tree that sends out individual stems from its roots to which other trees grow from and become clones. Cohesion - When a substance, such as water, is attracted to, or sticks to itself. Compounds - Refers to something composed of two or more elements. Condensation - A process in the water cycle when water vapor rises in the atmosphere, it cools off as it passes through air with cooler and cooler temperatures. As the water vapour cools, it changes from gas to liquid and the condensing water vapour forms tiny water droplets that make up clouds. Coniferous Tree - Trees that have needles instead of leaves (such as pine trees). Deciduous Tree - Trees that have leaves that change colour and fall off in the autumn season (such as the trembling aspen). Defoliation - When there is a lack of leaves over small or large areas of the tree during warmer seasons. Dioecious - A plant (or animal) that has a male and female reproductive organ. Discolouration - In terms of TREE, discolouration refers to when the trembling aspen bark turns any colour other than a pale green or white. Early Wood - The lightly coloured, less dense wood that is created by initial rapid growth when the vascular cambium layer rapidly divides. Elements - The simplest substances found in the world and that make up all matter. Endodermis - The innermost layer of the cells, found in roots of trees. These cells are made of thick cell walls. This layer serves to regulate water and nutrient movement between the soil and the vascular tissue. Epidermis - The outer layer of tissue in a plant. Evaporation - During the water cycle, this step is when the sun heats up bodies of water, and the water changes from liquid to gas. Exodermis - Tissue in a root that is right underneath the epidermis layer. The exodermis replaces epidermis tissue as it wears away and dies off. Foul Smell - In terms of the TREE program, a foul or stinky smell is a sign that a tree is rotting and is unhealthy. Fungi - In terms of the TREE program, fungi such as mushrooms or mold, are a sign that a tree is unhealthy. Any fungal bodies will be visible around the trunk or higher in the bark or on leaves. Germination - The growth of a plant from a seed. Heartwood - A dark layer of wood composed of dead xylem cells and fiber bundles. Over time, the cells harden and becomes stronger, enabling the heartwood to be structural support for the tree. Infiltration - A process in the water cycle where water that remains on the earth’s surface is soaked up by the soil. Trees absorb water from the soil and transport it to the leaves through the stem.

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Inner Bark - A layer of bark beneath the outer bark that is composed of cells that transport sap and nutrients throughout the tree. As these cells age, they become outer bark. Late Wood - The later slow growth of the tree as it progresses towards winter. This later slow growth creates the darkly coloured, more dense wood. Mesophyll - Tree leaf cells are composed of parenchyma cells in long tube-like arrangements. Mesophyll cells make up the middle section of a leaf. Outer Bark - Composed of dead cells, this is the visible layer of bark and is commonly referred to as cork. Osmosis - The process of two fluids of different concentrations of a substance, mixing to reach equilibrium. Parenchyma Cells - These cells provide support and nutrients to phloem and xylem cells and make up the bulk of plant cells. Pericycle - A layer of tissue that lies just inside the endodermis. The pericycle serves as internal support and protection for the root and it also forms new lateral roots by dividing rapidly in a specific location. Phloem Cells - A collection of cells responsible for transporting water and nutrients up and down throughout the tree. Photosynthesis - The process by which plants convert light energy into chemical energy for food. Pith - The centermost portion of the tree and is composed of soft spongy parenchyma cells. The pith stores and transports water and nutrients throughout the tree. Precipitation - A process in the water cycle where as more water condenses into water droplets, the clouds continue to grow, until the cloud becomes saturated and too heavy. When this happens, the water droplets fall to the earth as rain, snow, or hail. Root Sprouting - A way trees reproduce by using a shared root system. In this process, new aspen trees sprout from the roots of a mature aspen tree. Root sprouting produces numerous trees or clones with identical genetic information, leading to a colony of trembling aspen. Run-off - A process in the water cycle where the rain or melted snow on the ground flows back into various bodies of water such as rivers, lakes, streams, and oceans. The water will then be evaporated again, starting the cycle all over. Sapwood - A layer of wood, composed of xylem cells, that is responsible for water transport and storage through the tree’s daily water cycle. As the cells mature and die off, the sapwood hardens and becomes more rot resistant, turning into heartwood. Stands - These are trees in areas within the forest that have been measured, mapped, outlined, and described as a distinct group of trees. Stands can be large or small, ranging from a few acres to hundreds. Trees within a stand will share similar characteristics such as age, size, condition, and species. Stoma - These are little natural openings in the epidermis that allow for regulated gas exchange between the tree and the atmosphere (stomata is plural). Transpiration - The process where plants allow water to evaporate from their leaves to pull up water from their roots. Tree Ring - Visual indicators of the annual and variable growth rate of trees. Vascular Bundle - This a bundle of xylem and phloem cells that are essentially the veins and arteries of the leaves. Vascular Cambium Layer - The one cell thick layer responsible for the tree’s radial or circular growth. Vascular Tissue - Large amounts of tissues that help transport nutrients and water throughout the tree. Xylem Cells - A collection of cells responsible for transporting water up the tree.