All tropical rainforests are located in a narrow belt that girdles the earth's equator. This belt is known as the "tropics."  In the tropics, constant sunlight, rain and high temperatures spell year-round life -- making the rainforests rich in a wide variety of plant and animal species.  In fact, tropical rainforests contain over half of all the living things known to man. 

photo M. Noonan

In the Eastern United States we have temperate forests. In these forests, plants bud and bloom in the spring and summer, when temperatures are warm and sunlight is available. Then, in the fall and winter, temperate trees drop their leaves and go dormant for the harsh winter months.  This leaf litter builds up on the forest floor, creating a stockpile of nutrients in the temperate soil. 

In contrast, the tropical rainforest lacks such a seasonal cycle. Here, sunlight, rain, and warm temperatures are fairly constant, meaning that plants germinate, grow, flower and seed year-round. These warm temperatures ensure that decomposition of dead leaves and other waste material occurs at a rapid pace in the tropics. Thus, the ecosystem of the rainforest has most of its nutrients stored overhead in the leafy canopy rather than underfoot in the soil, as it is in the temperate regions of the globe.