Characterization of Amazonian Soils An Analysis Jonathan Rhodes October 30 2002 pH The soil of the Amazon Rainforest Basin is typically acidic averaging around 4 9 pH of the soil seems to be relatively independent of soil depth but there is some evidence that pH increases with an increase in sample depth The Soil Profile The average particle size of the soil in the Amazon usually hovers around the 0 1 mm mark approximately equal to fine sand or silt However the particle size measurably decreases with an increase in sample depth until a mostly clay layer is reached as little as 50cm below surface The tiny particle size of clay makes it far less permeable to water and nutrients than the layers above it therefore the nutrient layer is usually referred to as the top few inches of Amazonian soil Some nutrients are leached to deeper soils I really don t understand how this works Nutrient Concentrations Volume As mentioned above only the top few inches of Amazonian soil is able to effectively hold nutrients and water As a result nutrient concentration i e Carbon Nitrogen is inversely proportional to soil depth However as it is Amazonian soil is already lacking in nutrients Most of the nutrients within the Amazon Rainforest are tied up within the bodies of its flora and fauna To expediate the transfer of what nutrients are available in the soil micro organisms i e Mycorrhizae form a symbiotic relationship with some of the Amazonian flora converting nutrients into a useful form in exchange for food A significant amount of carbon dioxide is trapped within the soil after thousands of years of absorption by Amazonian trees Underlying Bedrock The bedrock of the Amazon Rainforest actually lies approximately four kilometers below the Amazonian surface and is therefore not a significant factor in determining soil stability pH etc Nevertheless for the sake of completeness the bedrock is labeled as pre Cambrian rock Erosion Land Use Problems Solutions Reforestation does not seem to be a practical solution for saving the rainforest but would probably only be successful as a secondary solution on top of a bigger plan The problem is that current techniques for preparing land for agriculture deplete the soil of its nutrients and stability decreasing the viability of restoring its vegetations As well reforestation requires so much effort time and money that it will probably be impossible to reforest the Amazon as quickly as it is being deforested
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