Holdridge
In 1947, Leslie Holdridge published a life zone classification using indicators of:
- mean annual biotemperature (logarithmic)
- annual precipitation (logarithmic)
- ratio of annual potential evapotranspiration to mean total annual precipitation.
Biotemperature refers to all temperatures above freezing, with all temperatures below freezing adjusted to 0°C, as plants are dormant at these temperatures. Holdridge's system uses biotemperature first, rather than the temperate latitude bias of Merriam's life zones, and does not primarily use elevation. The system is considered more appropriate to the complexities of tropical vegetation than Merriam's system.
Read more about this topic: Life Zone