Holdridge Life Zone System
Name:__________________________
Introduction
The Holdridge life zone system classifies zones according to several abiotic factors:
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Average annual rainfall
Altitude
Latitude
Humidity
Potential evapotranspiration = the amount of evaporation that would occur if a sufficient
water source were available
Average biotemperature = mean of all temperatures between 30 and 0oC and all temperatures
above and below are adjusted to 30 or 0oC
This does not specify homogenous communities so there may be several vegetation types associated
with the different life zones due to varying soils or absence/presence of open water.
How to use
The variables potential evapotranspiration, annual precipitation and humidity provinces are read
diagonally following the direction of the numbers. Biotemperature and latitude and altitude belts are
read horizontally.
Questions:
1. Discuss why Holdridge’s chart, developed in Central America, could be used to classify
Australian ecosystems.
2. Describe the conditions where deserts are found.
3. Compare Wet Tundra with Thorne Woodlands.
4. A particular humid locality has a potential evapotranspiration ratio of 0.3, an annual
precipitation of 6000mm and a biotemperature of 24oC.
a. Identify what type of plant community should be present: ________________
b. Identify what latitudinal region this would be found in: ___________________