PLANEACION

Tropical forests are characterized by the greatest diversity of species. They occur near the equator, within the area bounded by latitudes 23.5 degrees N and 23.5 degrees S. One of the major characteristics of tropical forests is their distinct seasonality: winter is absent, and only two seasons are present (rainy and dry). The length of daylight is 12 hours and varies little.

Tropical forest photos

From left: Olympic Peninsula rain forest, Washington; Patria River, Costa Rica; Ranomafana National Park, Madagascar; Hawaiian forest.

Temperature is on average 20-25° C and varies little throughout the year: the average temperatures of the three warmest and three coldest months do not differ by more than 5 degrees.

Precipitation is evenly distributed throughout the year, with annual rainfall exceeding 200 cm.

Soil is nutrient-poor and acidic. Decomposition is rapid and soils are subject to heavy leaching.

Canopy in tropical forests is multilayered and continuous, allowing little light penetration.

Flora is highly diverse: one square kilometer may contain as many as 100 different tree species. Trees are 25-35 m tall, with buttressed trunks and shallow roots, mostly evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines (lianas), ferns, mosses, and palms are present in tropical forests.

Fauna include numerous birds, bats, small mammals, and insects.

Further subdivisions of this group are determined by seasonal distribution of rainfall:

evergreen rainforest: no dry season.

seasonal rainforest: short dry period in a very wet tropical region (the forest exhibits definite seasonal changes as trees undergo developmental changes simultaneously, but the general character of vegetation remains the same as in evergreen rainforests).

semievergreen forest: longer dry season (the upper tree story consists of deciduous trees, while the lower story is still evergreen).

moist/dry deciduous forest (monsoon): the length of the dry season increases further as rainfall decreases (all trees are deciduous).

More than one half of tropical forests have already been destroyed.

...