Most plants do very well in neutral soils. However, the majority of tropical soils are acidic, which means that native trees and plants have had to adapt to acidic soil conditions. The traditional agricultural solution to soil acidity is to dump tons of lime on the soil, in order to achieve a more neutral pH, without regard to the cost or the damage done to microfauna. The second issue is something called the cation exchange capacity or CEC of the soil.
CEC is measured on a scale of 0 to 50, with 0 being soil that has complete filtration or lixiviation of any nutrients, making for rapid drainage with no retention of any kind. In contrast, soil with a CEC of 50 is solid rock or clay, which does not allow for drainage, causing plants and their roots to drown. In the case of tropical soils the majority have a very low CEC. For example, the average effective CEC of soils at La Pedregoza is around 1, so pretty much total filtration of the soil with very little retention of nutrients, organic material or microfauna.
This explains why rainforest trees are complete recyclers, drawing the majority of their requirements from the atmosphere and from the deadfall of leaves, branches and other organic matter inside the forest.
They have very little dependence on the soil for their food requirements. When farmers cut down tropical rainforests and use its soil to try to grow crops, they find little success because of the poor nature of the soil. The textbook quotes soil authority Robert Pendleton as saying,. This pessimistic attitude is no longer a result of mere opinion, for in a number of widely scattered regions in the humid low latitudes agricultural scientists have been and still are seriously at work.
If the soil is so poor in tropical rain forests, how does such a dense array of shrubs and trees grow there? 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. For more information on tropical soils, including downloadable PowerPoints, assessment questions, and educational links, please visit the SCOOP!
Teachers Guide. For high school and introductory college students, gain a foundation about the world of soils with our book - Know Soil, Know Life. Visit the Society Store to learn more and purchase your copy today. Tropical Soils. Breadcrumb Home. Tropical Forests and Grasslands Savanna Tropical soils are formed in areas with high annual temperature and rainfall.
Climate The savannas are grasslands that have several months of dryness, followed by a rainy season.
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