EXERCISE 2: Tree Identification with a Dichotomous Key and a Tree Leaf Collection
Introduction:
Humans have a natural affinity for trees—it is a rare person who does not enjoy the shade, flowers, and fruits of trees. We adorn our yards, malls, parks, and cemeteries with them. An even greater satisfaction is experienced by those who can identify trees and know something about their natural history.
It is the objective of this exercise to acquaint you with a technique for identifying trees. One could thumb through a field guide on trees and identify a certain tree that way, but a faster more direct method is a dichotomous key. The word "dichotomous" means branching, so a dichotomous key is one that consists of a series of choices or branching possibilities that will lead you to the identification of a certain tree. This will challenge your ability to make correct decisions based on accurate observations. Once you can identify trees you will likely want to learn more about them. There is much information about trees on the internet and many tree books are available in the college library and public libraries.
The second phase of this exercise involves the collection, preservation, and labeling of tree leaf specimens. This is a fun way to learn about trees.
What You Will Need:
Printed key from http://www2.vscc.cc.tn.us/jschibig/tree%20key.htm
A field guide to trees that has range maps and descriptive information about trees in this region (from library or purchase at a bookstore , but not in VSCC's bookstore).
Ruler with metric units on it.
A hand lens (in kit), hand pruners or a knife.
Newspapers and a large heavy book for pressing/drying.
Stiff white paper, hole puncher, Elmer's glue, black ink pen, binder notebook.
Activity:
�First familiarize yourself with tree leaf characteristics. Go to: http://www2.vscc.cc.tn.us/jschibig/leaftypes.htm
�Collect 15 different tree specimens (must be native to Tennessee, no domesticated Apple, Pear, Peach, Cherry, Mimosa, Ginkgo, Blue Spruce, Pawlownia, etc.) from your yard, roadsides, or woods (secure permission from the land owner, if it is not your land).
�Do not collect from parks without permission; they are protected areas.
�For each type of tree, collect a twig which is a few inches long and has at least 3 or 4 leaves on it; if flowers or fruits are present, collect those too.
�Place the specimen for each type of tree in its own plastic bag, enclose a label with information on its collector, date of collection, location, and habitat. For example, the label information might be something like this: Collector-Jane Doe; Date-October 12, 2002; Location-On right side of Smith Road, ½ mile from its junction with Jones Road; Habitat-Mature woods on a north-facing slope.
�Try to identify each tree in the field with your printed key and field manual. In addition to the leaf and twig characteristics, the fruits and bark are useful features for identification.
�When you get home with your bags of tree specimens you should refrigerate the bags until you can complete the identifications and press them. At home, you should use the on-line key to check your identifications (illustrations are provided on the on-line key).
�After identifying the tree specimens, place the twig and leaf specimens and label for each species in between newspaper sheets; be sure one leaf is turned over to expose the bottom surface; if you have a large compound leaf, you can just press the one compound leaf and a small section of the twig, be sure to turn over one of the leaflets to expose the bottom surface and insert this between the pages of a large thick book. Let the specimens dry for about one week and then they are ready for gluing.
�Neatly glue each specimen onto a stiff white sheet of paper (letter size). Information should be neatly printed in the bottom left corner of the sheet; print the information in this order: scientific name and common name on top; below the name put the collector; below collector put the date; below the collector put location; and at the bottom put the habitat description.
�Punch holes in the sheet of paper and insert each sheet into a binder-type notebook.
�Insert a table of contents with your name, the name of each of the tree specimens and page numbers.
This tree collection will be your "lab report" for this exercise and is to be submitted when you take your first Lab
Test in Mattox-114 (see calendar). It is to be turned in to me on the day of the first Lab Test ( just before the test). It will be marked down 5 points for each day it is late. Also, for each misidentification, 3 points will be subtracted
.
On your first Lab Test, I will give you some tree specimens to identify with your key (be sure to bring your printed key with you). This will be worth quite a few points; so you should practice using your key a lot so as to be ready for the keying on the test.
If you turn in additional leaf specimens, you will receive 1/2 point for each correctly identified and correctly done specimen. A maximum of 10 extra points may be earned (20 native tree species in addition to the 15 needed for lab exercise # 3). These points will be added to your final lab average. The bonus specimens do not have to be turned in until the time of your second lab test , but the 15 needed for exercise # 2 are due at the time of your first lab test.