Editing Rainforest (section)

== Soils ==
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Despite the growth of [[vegetation]] in a tropical rainforest, [[soil quality]] is often quite poor. Rapid [[bacteria]]l decay prevents the accumulation of [[humus]]. The concentration of [[iron]] and [[aluminium]] [[oxide]]s by the [[Laterite|laterization]] process gives the [[oxisol]]s a bright red colour and sometimes produces [[mineral]] [[deposition (geology)|deposits]] such as [[bauxite]]. Most trees have roots near the surface because there are insufficient nutrients below the surface; most of the trees' minerals come from the top layer of decomposing leaves and animals. On younger substrates, especially of [[Volcano|volcanic]] origin, tropical soils may be quite fertile. If rainforest trees are cleared, rain can accumulate on the exposed soil surfaces, creating run-off, and beginning a process of soil [[erosion]]. Eventually, streams and rivers form and flooding becomes possible. There are several reasons for the poor soil quality. First is that the soil is highly acidic. The roots of plants rely on an acidity difference between the roots and the soil in order to absorb nutrients. When the soil is acidic, there is little difference, and therefore little absorption of nutrients from the soil. Second, the type of clay particles present in tropical rainforest soil has a poor ability to trap nutrients and stop them from washing away. Even if humans artificially add nutrients to the soil, the nutrients mostly wash away and are not absorbed by the plants. Finally, these soils are poor due to the high volume of rain in tropical rainforests washes nutrients out of the soil more quickly than in other climates.<ref>{{cite web |last1=Baird |first1=Dr. Chris S. |title=What makes the soil in tropical rainforests so rich? |url=http://wtamu.edu/~cbaird/sq/2013/07/12/what-makes-the-soil-in-tropical-rainforests-so-rich/ |website=Science Questions with Surprising Answers |access-date=11 April 2019}}</ref>