The temperate deciduous forest, or TDF, is a biome -- that is, a distinct and well-defined community of living things -- in which perhaps the most striking feature is the sharp change in leaf color in the fall. "Deciduous" means "falling off" -- in this case, in a certain season -- and "temperate" means "mild"; accordingly, TDFs are found chiefly in the eastern half of the U.S., much of Europe, eastern Asia, the southern tip of South America, eastern Australia and New Zealand.
Characteristics of the TDF
Deciduous trees, unlike evergreens, start to lose their leaves in late fall and shed them completely at the onset of winter, passing into a period of dormancy until spring. In early autumn, as the amount of sunlight in each day becomes smaller and smaller, the trees withdraw chlorophyll from their leaves, causing them to turn various shades of gold, orange and red. Examples of deciduous trees include various species of maple, the Ohio buckeye, the horse chestnut, the American ash, the paper birch, the hackberry, the yellowwood and the cottonwood.
The Five Zones
The TDF includes five recognized layers, or zones, each of which features different types of vegetation, from larger to smaller. The first zone is the tree stratum, 60 to 100 feet high and containing maple, ash, elm, beech and other trees. The second zone is the sapling or small-tree layer, home to plants such as shadbush and dogwood. The third is the shrub layer, where you'll find rhododendron, azaleas, mountain laurel and huckleberries. The fourth zone is the herbal layer, housing a few spring boomers. Finally, the fifth zone, the ground layer, includes lichens and mosses.
Alfisols: A Nourishing Soil
Under the American soil taxonomy system that includes 12 different soil types, most of the stateside TDFs give rise to alfisols, or brown-forest soils. Alfisols, which can be found in most of the U.S. but are concentrated especially in the Midwest, support 17 percent of the world's population -- over a billion people. These are moderately leached soils, and considered to have high fertility, which makes sense given that maple trees and the other broad-leafed species that pepper TDFs demand a lot of nutrients. Their high fertility is enhanced by the fact that TDFs by definition sit in mild climates with favorable weather for most of the year.
Ultisols: King of the Southeast
Ultisols, like alfisols, support a high fraction of the planet's population -- around 18 percent. But these are warmer-weather soils, and hence sit chiefly in the U.S. Southeast, ranging from northern Florida west to about Louisiana and north into Pennsylvania. They tend to be reddish or yellowish, owing to a high content of oxidized iron. Although nourishing, they have been degraded to a large extent as a result of the kind of farming done in the Southeast between Colonial times in the 18th century and the Civil War in the mid-1800s.