Characteristics of a Tropical Rainforest
Distribution of the Equatorial Climate
Distribution of the equatorial climate
- The tropical rainforest (TRF) biome is mainly found in a band between 15° north and 15° south of the equator within the equatorial climate zone
- Covering only 6% of the Earth's surface, the main areas of tropical rainforest ecosystem are in the following countries:
- Amazon which is the largest remaining rainforest on Earth usually associated with Brazil but covers parts of seven other countries
- Central America including parts of Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama
- Central Africa including Cameroon, the Central African Republic, the Republic of Congo, the Democratic Republic of Congo (DRC), Equatorial Guinea and Gabon
- Indo-Malaysia, including Malaysia, Indonesia and a number of other countries in South-East Asia
Tropical rainforest climate characteristics
Characteristics of Tropical Rainforests
Characteristics | Equatorial Climate |
Location |
Low latitudes Within the Tropics 23.5° north and south of the equator Amazon in South America, New Guinea, South-east Asia, Zaire Basin |
Annual Precipitation | Over 2000mm |
Temperature Range |
Low range of mean monthly temperatures - 26-28°C Constant high temperatures Diurnal range is about 7°C |
Seasons |
No seasons - hot and wet all year round |
Humidity |
High, usually over 75-80% |
Soils |
Many of the soils in the rainforest are latosols Due to leaching and rapid uptake of nutrients by plants the soils are not very fertile Nutrients are concentrated in the upper topsoil |
Biodiversity |
Tropical rainforests contain the highest biodiversity of plants and animals on Earth Estimates range from over 50% to 80% of the world's plant and animal species One 10km2 area can contain up to 1,500 flowering plants, 750 species of trees, 400 species of birds and 150 species of butterflies |
Climate Graph for Iquitos, Peru
Climate graph for Iquitos, Peru
Structure of the tropical rainforest
- The tropical rainforest has five distinct layers:
- Ground layer (0m)
- Shrub layer (3-4m)
- Under canopy (15m)
- Canopy (30m)
- Emergents (45-55m)
Diagram of Tropical Rainforest Structure
Typical structure of a tropical rainforest
- All parts of the tropical rainforest ecosystem are interdependent
- A change in one part affects others
- Deforestation leads to the loss of habitats and reduction in biodiversity
- Loss of trees also impacts the nutrient cycle
Nutrient cycle
- Tropical rainforests have a continual growing season with high rainfall and temperatures all year round
- The nutrient cycle is rapid
- Trees and plants lose their leaves all year round
- The high level of moisture and high temperatures leads to rapid decomposition and recycling of nutrients
- Plants grow quickly which leads to a rapid uptake of nutrients from the soil
- Most of the nutrients are stored in the biomass
- Few nutrients are stored in the soil and the litter
Nutrient Cycle Within a Tropical Rainforest
Tropical rainforest nutrient cycle
- The result of this rapid nutrient cycle is that the soil in the tropical rainforest is not very fertile
Soil
- Soil is an important factor in the development of vegetation within the rainforest ecosystem
- The climatic conditions of rainforests, result in deep soils
- The soils rely on the rainforest to maintain fertility
- Nutrients leach away quickly when the forest is felled and the layer of humus is no longer being replaced
- Soils are some of the least fertile in the world because:
- Heavy rain causes rapid leaching of nutrients
- The layer of topsoil and organic matter is thin
- The soil is acidic due to the leaching of nutrients
- Rapid plant growth means that any nutrients are rapidly taken up by the plants
- There is a lack of weathered rock due to the depth of the soil
Soil Profile of a Tropical Rainforest
Soil profile of a tropical rainforest
Worked example
Why are tropical rainforest soils considered to be amongst the poorest in the world?
(3 marks)
Answer:
- There are fewer nutrients in the soil/ not very fertile (1)
- Thin layer of topsoil / organic matter / humus (1)
- Torrential / heavy rain leaching them out of the soil (1)
- Soils become acidic (1)
- Nutrients are taken up by plants quickly (1)
- Lack of nutrients from weathered rock/ deep subsoil (1)
- Undisturbed soil (1)
Water cycle
- Precipitation is intercepted by the rainforest canopy
- This protects the soil from erosion
- Water on the trees and plants evaporates rapidly due to the high temperatures
- This leads to cloud formation and high levels of precipitation
Exam Tip
It is important to understand the role of nutrient recycling in the tropical rainforest. Understanding this means that you will be able to clearly explain why deforestation has such an impact in rainforest areas.