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Trees, Trees and More about Trees v3 all rights reserved
There are two major types of trees in the Center. Conifers and the Broadleaf trees.
Conifers, or evergreen trees, are scientifically classified as Gymnosperms (In Greek gymnosperm = “naked seed”). Gymnosperms are plants with a vascular, or circulatory, system and have no flowering parts. Their seeds are produced on the scales of female cones, rather than inside fruit. Conifer leaves are needle, or scale shaped. Finally conifer “leaves" stay on the tree year around. (… except for Western Larches, but there are none in the Center yet!) Some examples of the Gymnosperms seen in the Center are the Western Red Cedar, Douglas Fir, Noble Fir, Western Hemlock, Pines, and the Pacific Yew.
Douglas Fir male cone
Douglas Fir female cone
Big Leaf Maple Flowers
Big Leaf Maple Seed
Broadleaf trees are scientifically classified as Angiosperms (In Greek angiosperm = “enclosed seed”). Angiosperm (Broadleaf) trees have a vascular, or circulatory system, produce flowers, and develop covered seeds. All Angiosperms (trees and plants) surround their seeds with an ovule or “fruit” (ex: nut, apple, cherry, etc.) Broadleaf tree leaves usually change color, die, and fall off every autumn. Any tree, like most Broadleaf trees, that lose their leaves in the seasonal fall are called deciduous. In science there are always a few exceptions, so a few broadleaf trees, like the Pacific Rhododendron, hold their leaves year around. Some of the many Angiosperms in the Center are the Red Alder, Big Leaf & Vine Maples, Pin Oak, Hooker Willow, Mountain Ash, Pacific Dogwood, Crabapple, and Chokecherry.
Hardwood vs Softwood trees. Generally wood from Conifers is called softwood while wood from Broadleaf trees is called hardwood. However, the wood from some “softwoods are very hard, and vice versa. Go figure!
Trees have three main parts, the roots, stem, and leaves (or needles). Each part depends on the other to survive. The roots are a tree’s foundation. Roots hold a plant steady and take in water (H2O) and nutrients from the soil. The stem, or trunk in a tree, provides stability and height for the branches. The trunk also allows water and nutrients to flow throughout the tree. The leaves and needles are out in the sunlight. The leaves and needles absorb sunlight and CO2. Together with H2O from the roots, chloroplasts inside the leaves and needles conduct photosynthesis and make food (sugars) for the tree. Situated mainly on the outside areas, are a tree’s flowers (Angiosperms), or male & female cones (Gymnosperms) which allow the tree to reproduce.
Most of us know that plants, including trees make their own food (energy) in their leaves or needles by photosynthesis. However, many people don’t know that trees have “wooden” circulatory systems. Lets find out what a tree’s circulatory system is made of and how it works.
Inside each tree is a circulatory or vascular system made of three types of plant tissue. The vascular system transports water and dissolved sugars and minerals up and down the tree. This system is made up of three basic types of tissue. These three parts are called xylem, cambium, and phloem. The xylem, cambium, and phloem grow sandwiched together.
- Xylem is the innermost layer of the three circulatory tissues.
- Cambium is the thin layer found between the xylem and phloem.
- Phloem is the outermost layer, found outside the cambium, just inside the protective bark.
Let’s look at these three vital parts of the tree in detail.
Xylem. Most of the tree is made of wood, or xylem. Xylem provides the support structure of a tree and part of the tree’s circulatory system. Xylem consists almost entirely of dead cells. The living xylem is the very thin outer ring, or layer, of xylem which makes up the present year’s tree ring. Xylem is made of small, thin cells shaped like tubes stacked end for end. Xylem tubes begin in the roots and go all the way up the tree. Living xylem cells act as a tree’s plumbing system. This system transports water and dissolved minerals from the soil next to the roots up to the trunk to the branches. The living xylem transports water and minerals for only one year. After a year the xylem dies and becomes wood (dead xylem) while a new outer layer of living xylem forms.
Cambrium. A thin layer of Cambium surrounds the outermost ring of the living xylem. Cambium is made of a few layers of living cells that produce both new xylem and phloem. Since cambium makes xylem and phloem, cambium is actually the layer that is responsible both for increasing the diameter of the tree and for keeping the tree alive! Cambium doesn’t produce xylem at a steady rate. This growth varies with temperature, amount of moisture, and amount of sunlight. That’s why tree rings vary in size.
Cambium produces lots of xylem in spring to early summer when it is warmer, wetter, and there is more sunlight. Less xylem is made in the summer because it is dryer, hotter, and there’s more sunlight. Each year's growth can be easily seen because of this varied growth pattern. That’s because there is contrast in color between the thicker lighter xylem elements produced in the spring, and the thinner, denser xylem elements produced in the summer. The lighter and darker rings make up one year’s growth. The name for each light / dark ring is an annual ring. Scientists count up the annual rings on a tree to tell how old the tree actually is/was. The variation in width in a tree’s rings over years can tell scientists when there were good growth years, or poor ones. There a couple ways to get tree data. One way to get and analyze a tree’s ring data is to actually cut down the tree. Another way to get this data is to take a tree corer and bore out a small, pencil thin rod of wood from the tree. It sounds bad, but this coring process actually doesn’t hurt the tree.
Coring a Douglas Fir
Tree growth can vary a lot in different environments. These 3 tree cookies are from trees of the same species & same AGE!
A thin, but very important, layer of tissue, called Phloem, surrounds the outside of the cambium layer.Phloem is made of hollow living tube like cells that form an energy, or food, transport system. The phloem has tubelike cells that act as pipes to transport dissolved sugars, or sap, from the leaves to the rest of the plant. These sugars provide energy to the different parts of a tree. Sugars are made in the leaves/needles by combining water, CO2 and sunlight to make sugar and oxygen in a process called photosynthesis. The sap is a watery solution, rich in sugars.
Bark, protection for the tree. Bark is produced by another thin layer surrounding the phloem called cork cambium. Cork cambium produces cork, a tough protective material that eventually becomes bark. The bark provides a protective barrier for the tree. Damage to the bark allows pests and pathogens to attack the vital inner layers of the tree.
A tree will die when the cambium layer is cut through all the way around the tree. When the cambium is cut all around the tree, the tree can now longer transport sugar, water, and nutrients. So it’s best to avoid damaging the outside of any tree. After all, trees have rights too!
Pacific Yew Tree cookie showing Heartwood
More about tree rings. Growth rings (or "tree rings" or "annular rings") can be seen in this horizontal cross section cut through the trunk of the Pacific Yew on left and the Douglas Fir below. Tree rings are more visible in areas where there are distinct seasons. The rings result from when there is a change in growth over the seasons of the year. One ring usually marks the passage of one year in the life of the tree.
Growth rings have two parts composed of both early and summer wood. The inner, and often broader, portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) due to warmer temperatures, precipitation, and sunlight. This section of the tree ring is known as "early wood".
The outer portion of the tree ring is called "late wood" (sometimes called "summer wood") and is more dense. The late wood portion of a growth ring is often narrower due to summer growing conditions being harsher then the spring.
Some trees, like the Pacific Yew shown above, have a broad inner, darker colored area of the wood. This area is called heartwood. Heartwood is very resistant to decay.
Douglas Fir "tree cookie"
Width of tree rings. Young, rapidly growing trees developbroad tree rings. Over time, all trees begin to develop smaller and smaller treerings if the growth rate is the same. That’s because the tree is growing about the same amount, but the growth is spread over a larger area. However, the size of the tree rings can vary greatly due to the growing conditions each year. Years withadequate moisture, and a long growing season will result in a wide ring being formed, while drought years usually result in verynarrow rings.
A year-by-year record, or ring pattern, is formed in the wood during a tree's life. A ring pattern can tell a researcher a lot about the tree and about past history. Each ring pattern reveals a large amount of data about local growth patterns and the climate. That’s because the ring pattern shows the climatic conditions in which the tree grew. Also, rees from the same region tend to develop the same patterns of growth for a given period. Information about the growth pattern of different tree stands allows a Forester to identify stands of trees that are stronger and ones of the same species that are not so strong. Stands of not so strong trees are harvested early to allow the stronger trees to grow faster.
Please answer these questions in CQC sentences that reflect each question.
1. Describe three key characteristics of Gymnosperms.
2. Tell two differences between Gymnosperms (Conifers) and Angiosperm (Broadleaf) trees.
3. Which trees are generally termed as Hardwood and which are termed as Softwood?
4. Describe the function of the following tree structures…. A. Roots B. Stem (trunk) C. Leaves
5. Tell the name and location of the three main parts of a tree’s “wooden” circulatory system.
6. Xylem is a very important part of the tree. Tell the function of xylem AND also how much of the tree is living xylem vs. dead xylem.
7. Tell the two main functions of Cambium and why it is so important to the tree.
8. Explain why a tree’s annual rings have both light and dark areas.
9. Tell the function of a tree’s phloem.
10. Explain
a. What sap is used for,
b. What sap is, and
c. How sap is formed.
11. Describe what tree structure produces bark AND explain what function bark serves.
12. When is the inner portion of a tree’s growth ring formed, AND why is it usually larger?
13. Why might the inner portion of a tree’s ring growth NOT be broader then the outer portion. (Thought question !!)
14. Tell where to find heartwood in a tree AND tell one fact about heartwood.
15. Explain why a tree’s rings normally get smaller in diameter over time.
16. Tell how researchers can use knowledge about tree rings to know what the climate was like hundreds of years ago.
17. Bonus EC Tell which of the trees in the Center are:
a. Gymnosperms or Angiosperms
b. Hardwoods or softwoods,
c. Broadleaf trees and which are Conifers.
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