Temperate Rainforest - Definition

Definition

For temperate rain forests of North America, Alaback's definition is widely recognized:

Annual precipitation over 1400 mm;

Mean annual temperature is between 4 and 12 °C. (39 and 54 °F).

However, required annual precipitation depends on factors such as distribution of rainfall over the year, temperatures over the year and fog presence, and definitions in other countries differ considerably. For example, Australian definitions are ecological-structural rather than climatic:

Closed canopy of trees excludes at least 70% of the sky;

Forest is composed mainly of tree species which do not require fire for regeneration, but with seedlings able to regenerate under shade and in natural openings.

The latter would, for example, exclude a part of the temperate rain forests of western North America, as Coast Douglas-fir, one of its dominant tree species, requires stand-destroying disturbance to initiate a new cohort of seedlings. The North American definition would in turn exclude a part of temperate rain forests in other countries.