Forestry Chapter 5 Essay:
Outline the six horizons in a soil profile and briefly describe four of the six.
A soil profile is a description of soil textures in different horizons or layers. A complete soil profile contains six basic layers, which each layer represented by a letter. See the diagram below which was taken from the following website: http://www.enchantedlearning.com/geology/soil/
Note: I had space, so I briefly described all 6 layers.
The O-Horizon layer is the top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter).
The O-Horizon layer is more evident in forest soils than agricultural soils because of the leaf litter found in forest soils. The A-Horizon layer is composed of topsoil consisting of a mixture of humus and mineral soil. Many shallow-rooted plants are concentrated in this layer. The E-Horizon layer is composed mostly of sand and silt, and is lighter in color than the O or A layers, having lost most of the clay, minerals, and humus through a process called “eluviation”, as water drips through the soil. The B-Horizon layer, or subsoil layer, contains the clay and mineral deposits that have leached out of the A and E Horizon layers. According to our text book, this layer of “translocated soil components” is also known as the “illuviation” layer. Subsoils in this layer that are high in build-up of clay are poorly drained, which adversely affects the growth of plants with deep root systems. The C-Horizon layer consists of slightly broken-up bedrock. Very little organic material makes its way into this layer, and neither do plant roots penetrate this layer. The R-Horizon layer is un-weathered bedrock composed primarily of granite, limestone, and sandstone. It is worth noting that not all soils have all six layers.
... that develop layers or horizons in the soil profile. These processes involve additions, losses, transformations and translocations of material that compose the soil. Minerals derived from ... quickly on basaltic lava, even though there is very little organic material. The plants are supported by the porous rock as ...
Burton, D.L. (2008).
Introduction to Forestry Science, Second Ed. Thompson Delmar Learning. Pg 91-94.