Dendrology: Tree Parts and Functions

Forestry

A Tree Is…

• A tree is a woody plant that has a well-defined stem and a formed crown usually at least 8 feet tall.

• The three main parts of a tree are:• roots• trunk (a.k.a. stem or bole)• crown

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Roots

• The purpose of roots is to anchor the tree and absorb water and nutrients.

• Rootlets are the small branches that form off the main root.

• Root hairs are fine, hair-like roots that absorb water and nutrients from the soil.

• Pine trees lack root hairs so they have mycorrhizae fungi to serve that function.

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Roots

• A tap root is a large main root that grows straight into the ground.

• Lateral roots are roots that grow horizontally from the tree.

• Trees with shallow root systems or that are in heavily cut-over areas are at risk for windfall.

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The Trunk

• The purpose of the trunk is to conduct water and nutrients from the roots to the crown.

• Heartwood is the older dark-colored, center portion of the tree trunk.

• The wood at the core of the tree is dead so its purpose is only to provide strength to the tree.

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The Trunk

• Sapwood is the light portion of a tree cross-section and it is living.

• The living portion carries nutrients and also serves as storage for food synthesized in the leaves.

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Four Parts of the Trunk

• Heartwood – purpose is strength• Xylem – nutrient flow upward• Cambium – tree growth• Phleom – carries food downward

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The Bark

• The outer bark is a dead, nonfunctioning layer that’s purpose is to protect the living tissue.

• It is formed by a thin layer of cells called the cork cambium.

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The Crown

• The part of the crown that grows in height is the terminal bud.

• The purpose of the crown is to serve as the manufacturing part of the tree.

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Photosynthesis

• is the process of converting carbon dioxide and water into food for the tree using the energy of the sun

• Most of the water carried to the crown enters the atmosphere as vapor through a process known as transpiration.

• Water exits the tree through leaf pores called stomata.

• Respiration is the process of a tree consuming oxygen.

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Tree Growth

• The age of the tree can be determined by examining the trunk cross-section and counting the annual rings because each year produces one growth ring.

• Summerwood is the dark-colored area of a tree’s growth ring.

• Springwood is the light-colored area of the ring.

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Tree Growth

• Trees that are closely-spaced or subjected to drought or stress will grow slower and produce rings that are narrow.

• Trees that are well-spaced and have abundant rainfall will grow faster and produce rings that are wider.

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