A cloud forest, also called a fog forest, is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal 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
Characteristics In comparison with lower tropical moist forests, cloud forests show a reduced tree stature combined with increased stem density and generally the lower diversity of woody plants. Trees in these regions are generally shorter and more heavily stemmed than in lower-altitude forests in the same regions, often with gnarled trunks and branches, forming dense, compact crowns. Their leaves become smaller, thicker and harder with increasing altitude. The high moisture promotes the development of a high biomass and biodiversity of epiphyte, particularly bryophytes, lichens, ferns (including filmy ferns), bromeliads and orchids. The number of endemic plants can be very high.
An important feature of cloud forests is the tree crowns can intercept the wind-driven cloud moisture, part of which drips to the ground. This water stripped from the clouds is termed horizontal or occult (because it is not recorded with normal rainfall measurement) precipitation, and can be an important contribution to the hydrologic cycle.
Due to the high water content of the soil, the reduced solar radiation and the low rates of decomposition and mineralization, the soil acidity is very high, with more humus and peat often forming the upper soil layer.
two general types of tropical montane cloud forests: * Areas with a high annual precipitation due to a frequent cloud cover in combination with heavy and sometimes persistent orographic rainfall; such forests have a perceptible canopy strata, a high number of epiphytes, and a thick peat layer which has a high storage capacity for water and controls the runoff;
* In drier areas with mainly seasonal rainfall, cloud stripping can amount to a large proportion of the annual precipitation
Importance of cloud forests * Watershed function: Because of the cloud-stripping strategy, the effective rainfall can be doubled in dry seasons and increase the wet season rainfall by about 10%. Experiments of Costin and Wimbush (1961) showed that the tree canopies of non-cloud forests intercept and evaporate 20 percent more of the precipitation than cloud forests, which means a loss to the land component of the hydrological cycle.
* Vegetation: Tropical montane cloud forests are not as species-rich as tropical lowland forests, but they provide the habitats for many species found nowhere else. For example, the Cerro de la Neblina, a cloud-covered mountain in the south of Venezuela, accommodates many shrubs, orchids, and insectivorous plants which are restricted to this mountain only.
* Fauna: The endemism in animals is also very high. In Peru, more than one-third of the 270 endemic birds, mammals, and frogs are found in cloud forests. One of the best-known cloud forest mammals is the mountain gorilla (Gorilla b. beringei). Many of those endemic animals have important functions, such as seed dispersal and forest dynamics in this ecosystems
Current situation In 1970, the original extent of cloud forests on the Earth was around 50 million hectares. Population growth, poverty and uncontrolled land use have contributed to the loss of cloud forests. The 1990 Global Forest Survey found that 1.1% of tropical mountain and highland forests were lost each year, which was higher than in any other tropical forests. In Colombia, one of the countries with the largest area of cloud forests, only 10-20% of the initial cloud forest cover remains. Significant areas have been converted to plantations, or for use in agriculture and pasture. Significant crops in montane forest zones include tea and coffee, and the logging of unique species causes changes to the forest structure.
In 2004, an estimated one-third of all cloud forests on the planet were protected at that time
Impact of climate change on cloud forests Because of their delicate dependency on local climates, cloud forests will be strongly affected by global climate change. A number of climate models suggest low-altitude cloudiness will be reduced, which means the optimum climate for many cloud forest habitats will increase in altitude. Linked to the reduction of cloud moisture immersion and increasing temperature, the hydrological cycle will change, so the system will dry out. This would lead to the wilting and the death of epiphytes, which rely on high humidity. Frogs and lizards are expected to suffer from increased drought. Calculations suggest the loss of cloud forest in Mexico would lead to extinction of up to 37 vertebrates specific to that region. In addition, climate changes can result in a higher amount of hurricanes, which may increase damage to tropical montane cloud forests. All in all, the results of climate change will be a loss in biodiversity, altitude shifts in species ranges and community reshuffling, and, in some areas, complete loss of cloud forests