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Holdridges Life Zones

Page history last edited by PBworks 14 years, 3 months ago

 Life Zones and Costa Rica



The concept of life zones was developed by Clinton Hart Merriam in 1889. A life zone is characterized as an enviroment where the plant and animal life share unique and similar characteristics. The concept of life zones in Costa Rica has been applied to land development and conservation, as it has been in many places. The life zones are breakdowns that help categorize research and organize thoughts about envoronments and ecosystems.



                                                       C. Hart Merriam




Merriam broke life zones down into these categories:


  • Lower Sonoran (low, hot desert)
  • Upper Sonoran (desert steppe)
  • Transition (open woodlands)
  • Canadian (fir forest)
  • Hudsonian (spruce forest)
  • Arctic-Alpine (alpine meadows or tundra)


This system was eventually criticised for being too impercise and in 1947 Leslie Holdridge revised the concept of life zones to create what is known as Holdridge's Life Zones.


Holdridge's sysem is a more complex classification system. Holdridge's life zones are predominately based on three factors: Median Annual Biotemperature, Annual Percipitation, and Annual Evapotranspiration (water evaporated that will become rainfall). These factors are ever changing, which is why Holdridge's system is useful for predicting enviromental change.


Visual Representation of Holdridge's Life Zone System




In Costa Rica, 12 of the life zones are present. I have been emailing research groups to try to discover what the last ecosystem (the unknown one) might be, but so far, efforts have been fruitless! There may be some discrepency because one of the ecosystems may fit into two seperate life zones, causing them to classify it as 2. That is my best guess!


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