Why is tropical topsoil thin

Category: Earth Science Published: July 12, Actually, the soil in tropical rainforests is very poor. You would think with all that vegetation, warmth, and moisture that the soil must be very rich. But the truth is otherwise, as people who live in these regions are well aware. Because it is so warm, when a creature dies, it is immediately decomposed and turned into new plant growth. There are some creatures that spend their entire lives never touching the soil! A lot of fruit bananas, mango, papayas, etc.

The topography here varies from flat, swamp like regions to steep mountain cliffs. These soils were formed by bedrock that has weathered in place over a long period of time, or from river sediments. Slash and burn shifting cultivation agriculture is commonly practiced in this region. A forest is cut for fuel for cooking fires. The remaining vegetation is then burned off. This process releases nutrients from trees that plants need to grow.

The area is cropped for a few years until the nutrients run out, and then will be abandoned so vegetation can grow. After years, the land owners return again. However, because of an increase in people needing food, the farmers are forced to return to lands before they are ready.

This can cause soils to become too poor to even grow native vegetation. This is called deforestation.

Without vegetation, the soils dry out and become desert like, even though they get plenty of rain. This can cause severe erosion. The savannas are commonplace in the Sahel region sub-Saharan Africa.

Answer: Earthworms are especially important because they dig through the soil and give the roots of plants places to grow, and make spaces for water and air to get into the soil.

Just below the topsoil layer is the subsoil layer. This layer is made up of minerals and decomposed organic matter and it is also very dark in color. This is the layer that many plants roots grow in. This layer has clay and mineral deposits and less organic materials than the layers above it. This layer is also lighter in color than the layers above it.

The soil horizon, O, starts at the topsoil and the other horizons are below it. Horizon R is the deepest horizon, which represents the bedrock at the bottom of the soil, but it is not actually a component of the soil and consists mainly of rock.

The 7 Soil Horizons Source: Flicker under creative commons.