land of small trees begins as the wet season reaches 

 about 500 mm (20 inches) of rain per year. As the rain- 

 fall increases and the dry season shortens, the height of 

 the forest increases. A wet season with a full meter (39 

 inches) of rain a year can support a forest with trees 

 over 60 feet high, but most of the trees will lose their 

 leaves during the dry season. These deciduous forests 

 may resemble our own temperate forests in the height 

 and form of the trees. 



As the rainfall further increases the forests change 

 from deciduous to evergreen and the treetops reach 150 

 feet in height. These evergreen "rain forests" support 

 the richest assemblage of species found in any biome on 

 earth. With moisture and warmth throughout the year, 

 and with habitats ranging from the dark forest floor to 

 the sunny high canopy, the lowland rain forest is the 

 most luxuriant example of life on earth. Such forests 

 can support between 300 and 400 different species of 



large trees in the same small tract, and the numbers of 

 insect species these trees harbor must number in the 

 thousands. No other habitat, not even the coral reef, 

 can support as many coexisting species as the lowland 

 rain forest. 



The small deciduous woodland, the deciduous 

 broad' leaf forest, and the tall evergreen rain forest dif- 

 fer in stature and percentage of deciduous plant species. 

 They also differ in the species themselves. Few rain for- 

 est plant species are also found growing within the 

 deciduous forest. Likewise, most plant species of the 

 deciduous forest are confined to seasonally dry areas. 

 Here we find another important reason for tropical 

 species richness: different types of forests support a host 

 of different plant and animal species. 



But rainfall is not the only important factor affect- 

 ing tropical forest vegetation: temperature is another. 

 This may surprise those who think that the tropics are 



Large displays of flowers are rarely encountered in tropical rain forests wtiere species can flower any month of ttie year. Reserva Forestal de 

 San Rannon, Costa Rica, 



