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Mollisols of the world Mollisols are generally associated with the steppe biome. Mollisol is a soil type which has deep, high organic matter, nutrient-enriched surface soil , typically between 60 and 80 cm (24-31 in) in depth. This fertile surface horizon, called a mollic epipedon, is the defining diagnostic feature of Mollisols.
The primary river of the dunes is the Calumet River. Its three segments were once a single waterway, parallel to the Lake Michigan Shoreline. [4] On the east is Trail Creek in Michigan City, Indiana. The Calumet River is accessible at several locations. The upper reaches are viewable in the Heron Rookery. [2]
This is a large area covering 407,000 square kilometres (157,000 sq mi) from northern Illinois through most of Missouri, eastern Kansas, Oklahoma and into Texas.This area was traditionally a mixture of woodland and tall grass prairie, which as the soil consists of highly fertile mollisols, most of the area has been converted to farmland.
According to Theodore Roosevelt:. We have taken into our language the word prairie, because when our backwoodsmen first reached the land [in the Midwest] and saw the great natural meadows of long grass—sights unknown to the gloomy forests wherein they had always dwelt—they knew not what to call them, and borrowed the term already in use among the French inhabitants.
The natural communities in this region are a matrix of forest, woodlands, and prairie. Today, much of the open prairie and savanna communities have been lost due to fire suppression and agriculture. However, oak-hickory woodlands remain relatively common, and mesic forest is abundant along riparian areas. [citation needed]
The second sub-ecoregion is the Central USA Plains, an area of 253,665 square kilometres (97,941 sq mi), that has a landform of smooth plains. The majority of this region’s surface material is moraine with some lacustrine, and the soil consists of calcium enriched prairie soils and forest soils on moraine.
The Cross Timbers are contained within the WWF central forest-grasslands transition ecoregion. The woodland and savanna portions of the Cross Timbers are mainly post oak and blackjack oak on coarse, sandy soils; [4] fire suppression in recent years has increased forest density and allowed eastern redcedar to invade as well.
The tallgrass prairie, with moderate rainfall and rich soils, were ideally suited to agriculture so it became a productive grain-growing region. The tallgrass prairie ecosystem covered some 170 million acres (690,000 km 2 ) of North America.