Geography 140
Introduction to Physical Geography

Lecture: Classifying Plant Life Functionally

 IV. Functional classification.  Plants can also be classified functionally, 
     by lifestyle, in addition to the genetic taxonomies and structural 
     classifications presented earlier.  This one was devised by a Danish 
     botanist, Christian C. Raunkiaer, back in 1903, and it classifies plants 
     by how they survive rough seasons or catastrophes (e.g., fire), if any. 
     Okay, I promise to keep this one short!
     A. Phanerophytes are any tall plants visible all year round, which can 
        afford to carry their perennial buds well up in the air, at least 25 
        cm up. This, then, would include all trees, lianas, and virtually all 
        shrubs in the strictly structural classification.  Things don't get so 
        tough, so they can "let it all hang out."
     B. Chamaephytes are low growing plants that are visible all year round, 
        which carry their perennial buds anywhere from the ground to about 25 
        cm up.  They are capable of handling rougher environments than 
        phanerophytes because of their low stature (they are exposed to less 
        wind and some ground warming).  Examples include the small shrubs 
        found in the tundra climate.
     C. Hemicryptophytes die back to buds at ground surface during the rough 
        season.  Their perennial buds lie close to the ground surface (above 
        or below) and they are often hidden by litter in the rough season, 
        which protects them.  So they are "half-hidden" plants.  This would 
        include many forbs, perennial grasses, and ferns.
     D. Geophytes die back to underground structures, such as bulbs, corms, or 
        rhizomes, during the challenging times of the year.  They would 
        include a lot of forbs in the strictly structural classification.  
        Examples would include lilies, onions, garlic, potatoes, that sort of 
        thing.
     E. Epiphytes we've already met in the structural classification.  These 
        are plants growing on top of other plants, their perennial structures 
        above ground.
     F. Therophytes are the plants that get through bad times (seasonal or 
        even years long) as seeds or spores.  They go through their entire 
        life cycles, from seed/spore to seed/spore, within one growing season, 
        which can be amazingly short.  Annual grasses would be an example, as 
        would the ephemeral (very short-lived) forbs that put on the desert 
        and tundra and alpine meadow wildflower displays.

Well, that's about it for life classification, folks.  So, in the life 
classification lectures (lectures 24-26), you've become acquainted with the 
genetic approach to classification, which was illustrated by the Linnaean 
binomial nomenclature and the alternative binary cladistic system under 
development at the present time.  You next met the life form classification 
for plants, which illustrated the structural or formal approach to 
classification.  In this short lecture, you also met Raunkiaer's version of 
the life form system for plants, which is more of a functional approach to 
classification (classifying plants by how they survive hard times and 
disasters).  

So, these lectures introduced you to a major concern of any science, 
classification, and different ways of approaching the task.  It also 
introduced you to the terms that will be used when I get around to describing 
and illustrating major vegetation associations around the world, the biomes.  

Document and © maintained by Dr. Rodrigue
First placed on web: 10/30/00
Last revised: 04/04/01