The grasslands of North American are called as prairies; they cover about 1.4 million square miles or 15% of the continent. They are widely scattered for about one thousand miles in the very center of North America, from the Rocky Mountains to Indiana. Accordingly to the amount of rainfall and temperature there are three types of prairies grasslands: tall grass prairie in the east, mixed grass prairie in middle part and short glass prairie in the west. Grasslands are growing in areas of limited precipitation with moderate temperatures changing from -20 to 110 F, precipitation varies during the year in range of 15-100 cm, the amount of rainfall decreases from east to west. The soil of the grasslands varies from a few centimeters in the west up to two meters deep in the east of prairies; it is deep and black, with fertile upper layers, productive and rich in nutrients. As to organic content, soils are changing from a brown to a dark brown. Taller-grass prairies have brown soils, which are richer in humus.
Native vegetation advantaged high quality of the soils, but due to developing agriculture large soil erosions occurred affecting the fertility of soils. Another important aspect of this biome is that the massive of its biomass is located in soil, in the root system of grasses. These enormous underground systems allow grasses to extend around a larger territory; they also serve as an effective adaptation to the low-moisture soil levels of the prairie. Grasses are dominating plants in prairies, there are several prevalent genera represented by a great number of species, one of two of which are dominative. The frost-free season in prairie averages 100 – 300 days a year. Climate of the eastern part of tall grass zone is gentle, summers are humid and cool, and winters are relatively warm, that is favorable for smooth development of the plants. In spring, new grasses appear and go green, the forbs are in bloom, and in midsummer, leaves of the tall grasses gain beautiful shades of yellow, orange, and brown, in autumn times seeding, and dying plants dominate.
The Term Paper on Different Types of Soils in India
1. Black soils The principal region of black soils is the Deccan plateau and its periphery extending from 8°45’to 26o north latitude and 68o to 83o45′ east longitude. They are formed from Deccan basalt trap rocks and occur in areas under the monsoon climate, mostly of semi-arid and sub-humid types. The overall climate of black soil region may be described as hot and dry summer, 40-100 ...
Life in prairie is maintained by small and big grazing animals, activity of which also increases in warm time of the year and calms down in winter. In the middle and west parts climate is dry and tough, winters are snowy and very cold, and summers are backing-hot, so grasses are small and resistive to such weather conditions. Besides, drastic changes of daily temperature during the whole year in this territory of grasslands causes droughts, strong winds, hails, hurricanes and other natural cataclysms, it shortens the period of organisms life in this zone. Grasses are adopted for such challenges by their developed and deep root systems, which keep them on soils. In addition, grasses have very strong and low bases, from which leaves grow, so even if upper levels get damaged or burnt, grasses can reproduce very fast and in full volume. Animals (including even birds) dig burrows or simply change their locations avoiding zones of danger.
One more challenge of organisms in this biome is frequent fires caused by lightening storms, especially in summer months. Because of stormy winds, fire gets quickly spread around on dry grasses and burns away huge territories, giving a place for new grasses to come. In times of such fires humans used to hunt big animals or launch new species of grasses used for food. These possibilities of being destroyed by fire or numerous grazing large mammals have formed the evolutionary adaptations of grasses. Even the process of reproduction of grasses, involving birds and small animals, which carry and plant the seeds, is one of effective adaptations to its environment. As the soils of North American grasslands are very good and productive, almost all of prairie lands were converted into commercial farms and altered for grain-growing. Farmers take over disturbed sites and supplant native species with technical and industrial crops. So, human factor can be also considered as a challenge for natural grasslands inhabitants. REFERENCES Paulson Dennis (University of Puget Sound), 1996, BIOMES OF THE WORLD Reveal, James L. (Norton-Brown Herbarium, University of Maryland), 1994 BIOMES OF NORTH AMERICA.
The Term Paper on Zoos: Animals in Captivity
A zoo is a place where animals live in captivity and are put on display for people to view. The word “zoo” is short for “zoological park.” Zoos contain wide varieties of animals that are native to all parts of the Earth. It is an important debate whether animals should be kept in the zoos or not. Some say that it is necessary to capture them in order to protect them from poachers. Regarding all ...
