Temperate Grassland
Temperate grasslands are characterized as having grasses as the dominant vegetation. Trees and large shrubs are absent. Temperatures vary more from summer to winter, and the amount of rainfall is less in temperate grasslands than in savannas. The major manifestations are the veldts of South Africa, the puszta of Hungary, the pampas of Argentina and Uruguay, the steppes of the former Soviet Union, and the plains and prairies of central North America. Temperate grasslands have hot summers and cold winters. Rainfall is moderate. The amount of annual rainfall influences the height of grassland vegetation, with taller grasses in wetter regions. As in the savanna, seasonal drought and occasional fires are very important to biodiversity. However, their effects aren’t as dramatic in temperate grasslands as they are in savannas. The soil of the temperate grasslands is deep and dark, with fertile upper layers. It is nutrient-rich from the growth and decay of deep, many-branched grass roots. The rotted roots hold the soil together and provide a food source for living plants. Each different species of grass grows best in a particular grassland environment (determined by temperature, rainfall, and soil conditions). The seasonal drought, occasional fires, and grazing by large mammals all prevent woody shrubs and trees from invading and becoming established. However, a few trees, such as cottonwoods, oaks, and willows grow in river valleys, and some nonwoody plants, specifically a few hundred species of flowers, grow among the grasses. The various species of grasses include purple needlegrass, blue grama, buffalo grass, and galleta. Flowers include asters, blazing stars, coneflowers, goldenrods, sunflowers, clovers, psoraleas, and wild indigos.
2009-01-31 14:03:33 補充：
Precipitation in the temperate grasslands usually occurs in the late spring and early summer. The annual average is about 50.8 to 88.9 cm (20-35 inches). The temperature range is very large over the course of the year.
2009-01-31 14:04:25 補充：
Summer temperatures can be well over 38° C (100 degrees Fahrenheit), while winter temperatures can be as low as -40° C (40 degrees Fahrenheit).
2009-01-31 14:05:08 補充：
The fauna (which do not all occur in the same temperate grassland) include gazelles, zebras, rhinoceroses, wild horses, lions, wolves, prairie dogs, jack rabbits, deer, mice, coyotes, foxes, skunks, badgers, blackbirds, grouses,
2009-01-31 14:05:44 補充：
meadowlarks, quails, sparrows, hawks, owls, snakes, grasshoppers, leafhoppers, and spiders.
2009-01-31 14:06:45 補充：
There are also environmental concerns regarding the temperate grasslands. Few natural prairie regions remain because most have been turned into farms orgrazing land. This is because they are flat, treeless, covered with grass, andhave rich soil.
2009-01-31 14:07:29 補充：
Temperate grasslands can be further subdivided. Prairies are grasslands with tall grasses while steppes are grasslands with short grasses. Prairie and steppes are somewhat similar but the information given above pertains specifically toprairies—the following is a specific description of steppes.
2009-01-31 14:08:08 補充：
Steppes are dry areas of grassland with hot summers and cold winters. They receive 25.4-50.8 cm (10-20 inches) of rainfall a year. Steppes occur in the interiors of North America and Europe.
2009-01-31 14:08:46 補充：
Plants growing in steppes are usually greater than 1 foot tall. They include blue grama and buffalo grass, cacti, sagebrush, speargrass, and small relatives of the sunflower. Steppe fauna includes badgers, hawks, owls, and snakes.
2009-01-31 14:09:07 補充：
Today, people use steppes to graze livestock and to grow wheat and other crops. Overgrazing, plowing, and excess salts left behind by irrigation waters have harmed some steppes.
2009-01-31 14:09:55 補充：
Strong winds blow loose soil from the ground after plowing, especially during droughts. This causes the dust storms of the Great Plains of the U.S.
2009-01-31 14:10:52 補充：
Polar Bear ( 學名: Ursus maritimus )
Introduction ( 簡介 )
Polar bears are among the largest predators in the world.
2009-01-31 14:11:09 補充：
They range in color from pure white after a molt to a yellowish shade resulting from solar oxidation or staining by oil from seal blubber. Their skin, nose and lips are black in colour.
2009-01-31 14:11:32 補充：
Polar bears' long neck and narrow skull aid in streamlining the animal in water, and their large, flat and oar-like front feet make them strong swimmers.
2009-01-31 14:11:43 補充：
Their fur is thicker than any other bears even covering their feet, for warmth and traction on ice. Polar bears also have a thick layer of blubber which provides buoyancy and insulation.
2009-01-31 14:12:17 補充：
Diet ( 鍾意食ge野 )
Staples Almost exclusively feed on ringed seals and to a lesser extent bearded seals. Also eat walrus, beluga whale and bowhead whale carcasses, birds, vegetation and kelp.
2009-01-31 14:12:32 補充：
Behavior ( 習性, 同埋鍾意做ge野 )
Highly dependant on older stable pack ice in the arctic region, polar bears spend much of their time on the ice hunting, mating and denning. They are generally solitary as adults, except during breeding and cub rearing.
2009-01-31 14:13:07 補充：
Unlike brown bears, non breeding females and males do not hibernate or den in the winter.
2009-01-31 14:13:28 補充：
Pregnant polar bears need to eat a lot in the summer and fall in order to build up sufficient fat reserves for surviving the denning period, during which time they give birth to one-pound cubs and then nurse them to about 20-30 pounds before emerging from the den in March or April.
2009-01-31 14:13:53 補充：
** If you want to have more information, you can refer to
http://en.wikipedia.org/wiki/Polar_bear#Habitat
2009-01-31 14:15:10 補充：
Polar Bear ( 學名: Ursus maritimus )
2009-01-31 14:15:26 補充：
Introduction ( 簡介 )
Polar bears are among the largest predators in the world. They range in color from pure white after a molt to a yellowish shade resulting from solar oxidation or staining by oil from seal blubber. Their skin, nose and lips are black in colour.
2009-01-31 14:15:44 補充：
Polar bears' long neck and narrow skull aid in streamlining the animal in water, and their large, flat and oar-like front feet make them strong swimmers. Their fur is thicker than any other bears even covering their feet, for warmth and traction on ice.
2009-01-31 14:15:56 補充：
Polar bears also have a thick layer of blubber which provides buoyancy and insulation.
