Oak tree with epiphytes; Bali, Indonesia.
one thinks of tropical forests, images of tall giant trees come
to mind, with shrubs and groundcovers struggling in the dense shade
below the all-encompassing canopy. The air is still and vexingly
humid, filled with bugs and ravenous mosquitoes. This is the popular
idea of the lowland rain forest.
More images of cloud forests
Tree ferns in Oaxaca, Mexico.
Leptospermum flavescens on Mt. Ophir, Malaysia.
Mt. Santo Tomas, Philippines.
Cloud forests, a type of rainforest, occur on high mountains in
the tropics, generally between 2,000 and 3,500 meters, and experience
very different environmental conditions. As one ascends in elevation,
the hot steamy lowlands are left behind and several distinct vegetation
zones occur, including lower montane forest, cloud forest or upper
montane forest, and even an alpine zone if the mountain is high
enough. The height of the trees is much lower, and in fact, the
trees usually appear crooked and stunted, due to exposure to wind,
sun, and cold. Cloud forests are so named because they are often
shrouded in mist and fog. The high moisture level and cool year-round
temperatures foster plant communities rich in mosses, ferns, and
epiphytes, a habitat that scientists are beginning to study and
catalog with increasing interest.
Monochaetum humboldtianum, native to Venezuela.
How is it possible for tropical cloud forest plants to thrive
out-of-doors in Coastal California? If one looks into the origins
of familiar local garden plants like Fuchsia
one will find that many of the species we grow are native to higher
elevations in the tropics, in these cases the Andean foothills.
Section Vireya Rhododendron and
Aeschynanthus (lipstick plants) come from the montane tropics
of Southeast Asia, particularly New Guinea. These plants can grow
here because of striking similarities between coastal California's
climate and that of mountainous areas in the tropics. The temperature
variation between day and night and between summer and winter is
not very great in the tropics, even on tropical mountains. Coastal
California also has moderate temperatures year round due to the
ocean's strong influence - San Francisco is sometimes referred to
as "the air-conditioned city." Cloud forests are found
at elevations where water in moist rising air masses condenses creating
a shroud of mist and fog. The high moisture levels are comparable
to northern California's wet winters while a cool ocean current
off the coast creates summer fog which softens our Mediterranean
summer drought to the extent that it moves inland. Views from atop
tropical mountains are remarkable in their resemblance to panoramic
summer views of the Bay area with thick fog advancing and retreating
below higher hills and mountains.
Major areas in the world where cloud forests are still found include
southern Mexico, Central America, and all countries in tropical
South America. On the other side of the globe, cloud forests can
still be found in SE Asia, New Guinea, tropical Africa, Madagascar,
and some islands in the South Pacific.