A Comparison of Warm Climate Biomes: Tropical Rainforests, Grasslands, and Deserts

Bioma 1: Tropical Rainforest

Bioma 2: Tropical Grassland

Bioma 3: Desert

Equatorial Climate

Tropical Eastern Margins

Tropical Continental Climate

Desertic Climate

Location

In the tropics, within the equatorial climate belt, 5° either side of the Equator.

The Amazon and Congo basins and coastlands of Ecuador, West Africa, and extreme Southeast Asia.

Within the tropics, the eastern coasts of central America, Brazil, Madagascar, and Queensland (Australia).

Between latitudes 5° north and south of the Equator and within central parts of continents [the Llanos (Venezuela), the Campos (Brazilian Highlands), most of central Africa surrounding the Congo Basin, and parts of Mexico and northern Australia].

The hot deserts of the Atacama and Kalahari and those in Mexico and Australia are all located in the trade wind belt, between 15° and 30° north or south of the Equator, and on the west coasts of continents where there are cold, offshore, ocean currents.

Temperature

High and constant all year round. From 26°C to 28°C; no seasonal change.

Each day having 12 hours of daylight.

Evening temperatures rarely below 22°C.

Temperatures are generally very high; a slightly cooler season when the sun has migrated into the opposite hemisphere.

High all year round; a slightly cooler season when the sun is overhead at the tropic in the opposite hemisphere.

Diurnal temperatures to exceed 25°C.

Very extreme.

The annual range is often 20-30°C and the diurnal range over 50°C.

During the daytime, there are high levels of insolation.

In contrast, nights may be extremely cold with temperatures likely to fall below 0°C.

Annual Rainfall

Usually exceed 2000 mm and most afternoons have a heavy shower.

Violent storms: heavy rain, thunder, and lightning.

1500-1800 mm. A long humid season. A short dry season.

600-1500 mm. A long dry season. A short humid season.

Precipitation is extremely unreliable.

Rain, when it does fall, produces rapid surface runoff which, together with low infiltration and high evaporation rates, minimizes its effectiveness for vegetation.

Up to 250 mm.

Vegetation

Rainforest

• All-year growing season.
• Constant moisture budget surplus.
• Rapid decay of leaf litter and recycling of nutrients.
• Trees (mainly hardwoods) with an evergreen appearance.
• The tallest trees may reach up to 50 m; roots which emerge over 3 m above ground-level.
• The trunks are slender and branchless.

Rainforest

• All-year growing season.
• Constant moisture budget surplus.
• Rapid decay of leaf litter and recycling of nutrients.
• Trees (mainly hardwoods) with an evergreen appearance.
• The tallest trees may reach up to 30 m; roots emerge over 3 m above ground-level.
• The trunks are slender and branchless.

Tropical or Savanna Grassland Vegetation

• Closed savanna: mainly trees with areas of grasses.
• Open savanna: only scattered tufts of grass.
• Trees are xerophytic, or drought-resistant.
• Leaves: small, waxy, and sometimes thorn-like.
• Roots: long and extend to tap any underground water.
• Trunks are gnarled and the bark is usually thick to reduce moisture loss.

Vegetation has to have a high tolerance to the moisture budget deficit, intense heat, and salinity.

• Plants are xerophytic because of the lack of water. Roots to absorb nutrients.
• Many plants are succulents; they can store water in their tissues.
• Most plants have small, spiky, or waxy leaves to reduce transpiration.
• Roots are very long to tap groundwater supplies or to take the maximum advantage of any rain.