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Even though these types of forests are very different, their soil characteristics are very similar. Boreal forests are the evergreen forests that are far to the north, and transition into the tundras. There are also evergreen temperate forests, which are mixes of coniferous and deciduous plants. Temperate forests are primarily deciduous. There is also a small world area of temperate rainforests (think Seattle) are the areas that are home to the giant redwoods and sequoias.
Forest soils are formed under conditions that are not too wet, or too dry. The soils in temperate forests depend on the type of forests. The temperature ranges from high (like Florida) to very low (Northern Canada/Siberia).
Where parent materials are sandy, evergreen vegetation tends to dominate the landscape. This includes the boreal forests, and a majority of the evergreen temperate forests in New England and Northern Michigan and Minnesota. They are also common in Florida, and along the coast into the Carolinas. These forests have soils called Spodosols. They get a lot of rain, and when combined with a sand, the water leaches minerals and organic matter downward. This leaves an ashy white layers (E horizons).
Deciduous forests have soils called alfisols. These soils do not have a bleached E horizon, but do have clays that accumulate in the subsoils. Alfisols are very common in the Midwestern region, and are the most fertile type of forest soils.
In the Southeastern US, there are coniferous forests and temperate forests. But the soils here are MUCH older and more acidic. The moisture and humidity have caused most of the nutrient found in Alfisols to leach out, leaving behind the clays and oxides.
The organisms hosted does depend on the soils. But in a majority of the areas host trees of all different kinds, deer, songbirds, bears, wolves, squirrels, and salamanders. The largest fungus is the world is located under forest cover.
Topography can range from flat and swampy, to very steep. The parent materials can be glacial in origin, (like in the Boreal forests), ocean sediment (sands like Florida), wind or water transported, and can even be formed in place (like the Southeastern US). Sandy parent materials generate spodosols, and finer materials generate alfisols and ultisols.
These soils are youngest in the areas that were covered with glaciers. In areas like the Southeastern US, they are VERY old, like the soils in the Savanna of Africa.
The biggest threat to the forests in the US is urbanization. A majority of the east coast cities were once forested, then cut down and used for agriculture or building. Trees lock large amount of carbon dioxide into the air by trapping it as organic matter (and living trees). When a forest is cut down, these trees and their soils release the stored carbon into the atmosphere. Clear cutting trees also leave the soils vulnerable to erosion. However, there are now many sustainable harvesting methods that happen in forests to store carbon, and keep the soil in place.
Boreal forests comprise 17% of the world, and are only found in the Northern Hemisphere mostly in Russia and Canada. The remaining temperate and evergreen forests account for 8% of the land mass, and is found in most of continental Europe and the US East of the Mississippi. The temperate rainforest only accounts for 0.3% of the earths land, with very few portions that are undisturbed. It can be found primarily in the Pacific Northwest.
For more information on the forest soils, including downloadable PowerPoints, assessment questions, and educational links, please visit the SCOOP! Teachers Guide