Some of the abiotic factors found in a tropical rainforest are high temperatures, heavy rainfall, poor nutrient content in soil and sunlight that is found primarily at the tree canopy level while remaining limited at ground level. Because of the heavy overhead canopy, the forest floor may receive as little as 2 percent of the sunlight. Precipitation, which is a significant abiotic factor in a non-aquatic ecosystem, can range between 98 and 177 inches annually in a tropical rainforest.
Several abiotic factors are considered in categorizing an ecosystem as a tropical rainforest: the average temperature must be greater than 75 degrees Fahrenheit, the annual rainfall must be more than 98 inches and there must never be any occurrence of frost. The soil is typically poor in a tropical rainforest because the heavy rainfall washes away nutrients and it is usually acidic. Because of the soil conditions, many trees rely upon lateral root systems rather than deep tap roots.
Tropical rainforests play an important role in sustaining oxygen-dependent life on Earth. Although they only cover about 6 percent of the Earth's landmass, tropical rainforests are believed to be responsible for as much as 28 percent of the world's oxygen turnover. A massive amount of carbon dioxide is absorbed by tropical rainforests and converted to oxygen through photosynthesis. Deforestation, if it continues at its present rate, can have a significantly negative effect upon the worldwide carbon dioxide and oxygen exchange rate.