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MICHIGAN FORESTS FOREVER TEACHERS GUIDE

 


HOW TO USE A DICHOTOMOUS KEY    1-TreeSign.jpg (15307 bytes)

What is a "Dichotomous" Key?

"Dichotomous" means "two-way", or a fork-in-road.  A dichotomous key is a tool designed to distinguish the differences among a set of objects, in this case, a group of trees.  The key separates trees into various categories, based on physical characteristics, until there are only two species remaining.  It's sort of like a process of elimination.

The use of keys requires careful observation and usually involves the learning of some basic terminology.  Patience is often needed, especially the first few times working through the key.  These are excellent decision-support opportunities.  During the process, students learn quite a bit about trees, or whatever taxonomic group a key is designed for.  It is the beginning of a better understanding of trees, forests, and natural resources.

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MCF Benchmarks
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On-Line Tree Identification Keys

These are not common on the Internet, for some good reasons.  The larger the geographical area covered, the more species are involved.   More species means a more complex key and many more images and supporting documentation.  Increased complexity is increasingly problematic and expensive.   There are many excellent image sets on the Internet, but not many keys.   Image sets generally require that you know what you're looking for before you look.   A catch-22.

There are several good resources on the Internet.

1.  Tree ID Key for Michigan's Upper Peninsula - http://uptreeid.com

This MSU Extension website was designed specifically for students and forest owners.  There is a wealth of information about the trees of the U.P.  It is more than just a dichotomous key.  Applicability to southern Michigan is limited due to important changes in forest types.

2.  National Arbor Day Foundation Key - http://treelink.org/whattree/index.htm

This is a key to the more common trees (about 130) of the eastern and central USA.  It provides a good representation over a large geographical area. 

3.  An Atlas of Current and Potential Future Distributions of Common Trees of the Eastern United States
     http://www.fs.fed.us/ne/delaware/atlas/index.html

This fascinating USDA Forest Service website allows the user to look at the distribution of a given tree species under various scenarios of climate change. There is a large somewhat confusing number of possible scenarios, and there are limitations due to the assumptions involved in any prediction of this type.

4.  U.S. Forest Service "Silvics of North America" - http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm

A professional summation of nearly all commercial tree species in North America, divided into Conifers (~65 species) and Hardwoods (~130 species).  Also includes a glossary, tree characteristics, insects & mites, disease organisms, birds, and mammals. 

5.  PlantMaps - http://www.plantmaps.com

A clever tool that displays tree species ranges in the United States.  Plant Hardiness Zone maps can also be generated.  Pretty neat site but knowing the botanical names of species helps. 

 


Other Tree Information Resources

Botany.com - http://www.botany.com/index.html
University of Wisconsin Botany Collection - http://www.wisc.edu/botit/dendrology/
University of Wisconsin Virtual Foliage - http://www.wisc.edu/botany/virtual.html
Oregon State University Horticulture Collection - http://www.bcc.orst.edu/hort226/index.htm#gibi
Kellogg Biological Station Tree ID Cards - http://kbs.msu.edu/volunt/TOUR/index.htm
USDA Natural Resources Conservation Service Plants Database - http://plants.usda.gov/plants/
USDA Forest Service Silvics Manual - http://willow.ncfes.umn.edu/spfo/pubs/silvics_manual/table_of_contents.htm
TreeGuide.com - http://www.treeguide.com/
Texas A&M University Vascular Plant Image Gallery - http://www.csdl.tamu.edu/FLORA/gallery.htm

MSU Pub E-2332  "Identifying Trees of Michigan"
Peterson Guide  "A Field Guide to Trees & Shrubs"
Norman Smith  "Trees of Michigan and the Upper Great Lakes"
William Harlow  "Fruit Key & Twig Key to Trees & Shrubs" 
Linda Kershaw "Trees of Ontario"

 

Tree ID Pages:  ID Characteristics,   Michigan Tree Species,    ID Glossary

 

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MSUElogo.tif (16254 bytes) This website was developed and created by Michigan State University Extension for the teachers of the State of Michigan.  The website is maintained by the Delta-Schoolcraft Independent School District in support of the Michigan Forests Forever CD-ROM from the Michigan Forest Resource Alliance.

Page Name:  TreeBasics/TreeIDkeys.htm
Please provide comments to Bill Cook:  cookwi@msu.edu or 786-1575