Tree Inventory

Objectives

• Differentiate between species of trees
• Learn how to use a dichotomous key

Identify the major parts of a tree needed for identification.  

   Materials

Tree Finder: A Manual for the Identification of Trees by their Leaves, by Watts. 1998.

 

Introduction

Trees are some of the most important, useful, and beautiful objects found in nature.  We have trees and plants to thanks for the oxygen that we breathe.  Trees help stabilize soils, preventing erosion; trees provide shelter, food, and building materials for animals and humans; trees help remove pollution and greenhouse gases from our atmosphere.

 

A dichotomous key is a tool that allows someone to determine the identity of specimens found in nature such as trees, wildflowers, amphibians, or fish. Keys consist of a sequence of choices that lead the user to the correct identity. Dichotomous means “divided into two parts”. Therefore, dichotomous keys give two choices at each step. Using a field guide to trees and the iTree National Tree Benefits Calculator helps to identify trees and shows the significance of trees in terms of their environmental benefits, such as storm water management, increasing property value, energy efficiency, air quality, and carbon sequestration.

 

In this lab, we are going to use a dichotomous key to help identify a few of the trees on Triton’s campus.  A few of the most important decisions we will be faced with are:

• Does the tree have needles or broad leaves?
• Are the leaves simple (a single leaf per stem) or compound (having multiple leaflets on each leaf stem)? 
  • The leaflets may have their own stems. 
  • Look for a bud at the base of the leaf stem.  The leaf stem is usually curved and cupped because of the protruding bud.
• Do the leaves attach to the branch in an alternate pattern (on one side of the branch, further up the branch on the other side) or an opposite pattern (two leaves attach to the branch on opposite sides from each other)
• Are the leaves smooth, toothed (jagged edges), or lobed (bulges)?    

 Procedure

Examining leaves is one of the most common ways to identify trees. Leaves are very characteristic of a particular tree species. There are many clues to look for on a leaf to help identify the tree from which it came. These include leaf shape, leaf arrangement, and leaf margins. 

 

Broadleaf trees are very common in the United States. These trees have leaves with wide blades exposing a large surface area for photosynthesis (e.g. oaks and maples). Mostly, these trees are deciduous and drop their leaves in autumn.

 

The other type of tree is an evergreen tree. These have needlelike or scale-like leaves. Trees like pines and spruces have needlelike leaves, and trees like junipers and cedars have scale-like leaves. Generally, these leaves stay on the tree for more than a year.

Needlelike leaves have very little surface area; therefore, they are not able to capture much sunlight for photosynthesis. Needlelike leaves also have a thick coating to prevent excessive water loss. Trees with needlelike leaves are well suited to sites where water conservation is very important for survival. Because these needles last several years on a tree while broadleaves only live for one growing season, trees with needles have an advantage over broadleaf trees, in that the metabolic cost of leaf production can be recovered with photosynthesis over several growing seasons.

 

The shape of a tree’s leaves form over the course of a tree species’ evolutionary history. The shape gives the tree its best chance of survival based on the environmental factors in the ecosystem. A leaf’s task is to capture sunlight for photosynthesis, producing food for the tree. In this process, the leaf also receives heat. The shape of the leaf has therefore developed over time to balance these needs: maximizing sunlight but minimizing heat absorption and/or water loss.

 

Heart shaped leaves look exactly as the name implies – the leaf is in the shape of a heart. Obovate leaves are broadest above the middle and longer than they are wide. Elliptical leaves are broadest in the center and taper near the ends. Ovate leaves are broadest below the middle and longer than they are wide. Like the heart shaped leaves, the triangular leaves look as the name implies – the leaf is in the shape of a triangle. Lance leaves are much longer than they are wide (typically 4x longer), and although generally the same width throughout, they may be slightly wider in the middle.

 

There are other leaf shapes, depending on the source used. However, the ones mentioned are some very common, simple shapes.

Leaves can be arranged on a twig in one of three ways:

Opposite – leaves occurring in pairs at the nodes.
Alternate – leaves staggered or not directly across from each other.
Whorled – leaves occurring three or more on a single node.

The arrangement of the leaves minimizes the overlap between one leaf and another. This maximizes availability of sunlight and air. Opposite leaves usually have the adjacent tiers cross at right angles to minimize overlap. Alternate leaves are generally distributed in a spiral.

 

Most trees have alternate arrangement of leaves, making trees with the other two arrangements a limited group. In order to see the leaf arrangement, the leaves must be observed while still on the twig.

 

The margin of the leaf is the name for the shape of the edge of the leaf. A leaf that is smooth all the way around with no teeth or undulations has a smooth leaf margin. A leaf with a wavy or bumpy edge in the plane of the leaf is called rounded or sinuate. A margin with continuous, sharp teeth on the edge is finely serrated. 

 

Leaf teeth serve as clues in the process of leaf identification of a tree. In environments with sufficient water and nutrients, the percentage of toothed leaves correlates negatively with temperature, i.e. the higher the temperature, the lower the percentage of trees with teethed leaves. Therefore, in cold climates, leaves have larger and more teeth. Paleobiologists often use this in paleoclimate reconstruction.

 

When looking at a leaf with a broadleaf shape (as opposed to needle-like or scale-like), the next thing to look for is whether it is simple or compound. A simple leaf has one leaflet, a petiole (stalk) and a bud at the base of the petiole. A compound leaf has two or more leaflets and a bud at the base of the petiole. A once pinnately compound leaf has one main petiole and leaflets arranged pinnately on each side of the petiole. A twice pinnately compound leaf has one main petiole and then secondary petioles arranged on each side of the main petiole. The difference between a leaf and a leaflet can be checked where the leaf attaches to the stem. If there is no bud, then it is a leaflet and not a leaf        

  Unknown 1

Provide a quick sketch of a leaf from the tree you are identifying below. 

 

 

 

 

 

 

 

Leaves or Needles?	Leaf Arrangement (opposite, alternate, whorled)	Leaf Type (simple, compound, doubly compound)	Lobes (yes, no)

 

 

Using the Arbor Day dichotomous key website, https://www.arborday.org/trees/whattree/,

what species did you determine for this tree?

 

Common Name _______________________________________________________

 

Latin Name        _______________________________________________________

 

Estimate of Tree Trunk Diameter 4.5 feet above ground in inches _____________________

 

Open up the iTree for education software tool found at https://www.davey.com/arborist-advice/articles/national-tree-benefit-calculator/ created by the USDA Forest Service. Using the National Tree Benefits Calculator and the data collected on the trees, calculate the environmental benefit the above tree.

 

Estimated Yearly Benefits (in dollars)
Stormwater	Electricity	Air Quality	Property Value	Natural Gas	CO2

 Unknown 2

 

Provide a quick sketch of a leaf from the tree you are identifying below. 

 

 

 

 

 

 

 

Leaves or Needles?	Leaf Arrangement (opposite, alternate, whorled)	Leaf Type (simple, compound, doubly compound)	Lobes (yes, no)

 

 

Using the Arbor Day dichotomous key website, https://www.arborday.org/trees/whattree/,

what species did you determine for this tree?

 

Common Name _______________________________________________________

 

Latin Name        _______________________________________________________

 

Estimate of Tree Trunk Diameter 4.5 feet above ground in inches _____________________

 

Open up the iTree for education software tool found at https://www.davey.com/arborist-advice/articles/national-tree-benefit-calculator/ created by the USDA Forest Service. Using the National Tree Benefits Calculator and the data collected on the trees, calculate the environmental benefit the above tree.

 

Estimated Yearly Benefits (in dollars)
Stormwater	Electricity	Air Quality	Property Value	Natural Gas	CO2

 Unknown 3

 

Provide a quick sketch of a leaf from the tree you are identifying below. 

 

 

 

 

 

 

 

Leaves or Needles?	Leaf Arrangement (opposite, alternate, whorled)	Leaf Type (simple, compound, doubly compound)	Lobes (yes, no)

 

 

Using the Arbor Day dichotomous key website, https://www.arborday.org/trees/whattree/,

what species did you determine for this tree?

 

Common Name _______________________________________________________

 

Latin Name        _______________________________________________________

 

Estimate of Tree Trunk Diameter 4.5 feet above ground in inches _____________________

 

Open up the iTree for education software tool found at https://www.davey.com/arborist-advice/articles/national-tree-benefit-calculator/ created by the USDA Forest Service. Using the National Tree Benefits Calculator and the data collected on the trees, calculate the environmental benefit the above tree.

 

Estimated Yearly Benefits (in dollars)
Stormwater	Electricity	Air Quality	Property Value	Natural Gas	CO2

 

 

 

 

Unknown 4

 

Provide a quick sketch of a leaf from the tree you are identifying below. 

 

 

 

 

 

 

 

Leaves or Needles?	Leaf Arrangement (opposite, alternate, whorled)	Leaf Type (simple, compound, doubly compound)	Lobes (yes, no)

 

 

Using the Arbor Day dichotomous key website, https://www.arborday.org/trees/whattree/,

what species did you determine for this tree?

 

Common Name _______________________________________________________

 

Latin Name        _______________________________________________________

 

Estimate of Tree Trunk Diameter 4.5 feet above ground in inches _____________________

 

Open up the iTree for education software tool found at https://www.davey.com/arborist-advice/articles/national-tree-benefit-calculator/ created by the USDA Forest Service. Using the National Tree Benefits Calculator and the data collected on the trees, calculate the environmental benefit the above tree.