Forests protect the underlying soil from the directeffects of rainfall, generating what is generally anenvironment in which erosion rates tend to be low.The canopy plays an important role by shortening thefall of raindrops, decreasing their velocity and thusreducing kinetic energy. There are some examplesof certain types (e.g., beech) in certain environments(e.g., maritime temperate) creating large raindrops, butin general most canopies reduce the erosion effects ofrainfalls. Possibly more important than the canopyin reducing erosion rates in forest is the presence ofhumus in forest soils (Trimble, 1988). This both absorbsthe impact of raindrops and has an extremely highpermeability. Thus forest soils have high infiltrationcapacities. Another reason that forest soils have anability to transmit large quantities of water throughtheir fabrics is that they have many macropores pro-duced by roots and their rich soil fauna. Forest soilsare also well aggregated, making them resistant to bothwetting and water drop impact. This superior degreeof aggradation is a result of the presence of consider-able organic material, which is an important cementing agent in the formation of large water-stable aggregates.Furthermore, earthworms also help to produce largeaggregates. Finally, deep-rooted trees help to stabilizesteep slopes by increasing the total shear strength ofthe soils.
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