Grassland Types
There are several types of grasses in temperate grasslands. The three main types are wet prairie, mesic prairie, and dry prairie, and they are classified by the amount of precipitation they recieve; wet prairie recieving the most precipitation and having the worst drainage and dry prairie being the most arid of the three. Mesic prairies recieve a moderate amount of precipitation and have good drainage, making mesic prairies the most beneficial for agriculture. Because of this, very little natural mesic prairie remains untouched by humans.
Climate
Temperate grasslands are characterized by their hot summers and cold winters. Summer temperatures can reach well over 100F and winter temperatures can reach as low as -40F. Grasslands recieve much of their precipitation from early spring to summer and can get anywhere from 10-35 inches depending on their geography. For instance the long grass prairies of the North American Great Plains recieve an average of 21 inches of precipitation yearly, but the short grass prairies of the Great Plains only recieve 12.6 average yearly inches of precipitation due to the rainshadow effect of the Rocky Mountains.
Physical Characteristics
Temperate grasslands are dominated by stretches of grassy, flat land with few trees or large shrubs. Hills in grasslands typically don't rise more than 1.5 meters high. Grasslands, especially mesic temperate grasslands, have some of the world's most fertile soil. Grasses have adapted to grow very deep roots to reach water well below the surface. The death and decomposition of these deep, complex root systems is what gives temperate grasslands such nutrient-rich soil. Another unique adaptation of these prairie grasses is subsurface growth points, meaning the area between the roots and grassy tops of a plant from which the plant grows is slightly underground. This allows plants to survive occasional brush fires which destroy dead plant material above the surface and allow new plants to grow.
Human Impact
Because of the massive agricultural value of temperate grasslands, very few grasslands have been left untouched. The human population of the Great Plains in North America has grown more rapidly than the US population as a whole since the middle of the 20th century. This massive increase in population and the resultant urbanization has caused other dramatic changes.
American Bison
Before the arrival of white settlers, American Bison stretched from the Atlantic to the Rocky Mountains and from Canada to Mexico. In the early 1800s after rapid colonization of western North America and the American Great Plains, American Bison were over-hunted and quickly became endangered. By 1900 only a little over 1,000 bison were left, most being driven to higher altitudes near the Rocky Mountains. Yellowstone National Park took in many bison in an attempt to preserve the species, but by 1902 poachers had reduced Yellowstone’s herd to about 2 dozen. While the American Bison is no longer endangered and the population is on the rise, there are only an estimated 530,000 animals of the once 6-million estimate, and it is currently believed that freeroaming, completely genetically pure American bison can only be found in Yellowstone.