A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a high incidence of low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained.
Typically, there is a relatively small band of altitude in which the atmospheric environment is suitable for cloud forest development. This is characterized by persistent mist or clouds at the vegetation level, resulting in the reduction of direct sunlight and thus of evapotranspiration. Trees in these regions are generally shorter and more heavily stemmed than in lower altitude forests in the same regions, and the moisture promotes the development of an abundance of vascular epiphytes. This results in abundant moss and fern covering, and frequently flowers such as orchids may be found. Soils are rich but boggy, with a preponderance of peats and humus. Within cloud forests, much of the precipitation is in the form of fog drip, where fog condenses on tree leaves and then drips onto the ground below.
The definition of cloud forest can be ambiguous, with many countries not using the term (preferring such terms as Afromontane forest and upper montane rain forest, or more localised terms such as the Peruvian yungas, and the laurisilva of the Atlantic Islands), and occasionally subtropical and even temperate forests in which similar meteorological conditions occur are considered to be cloud forests.