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Nature Gallery (Eco Regions)

Temperate Grasslands
In the middle latitudes, grasslands occupy areas that are wetter than deserts but drier than forests. Annual precipitation is not only too low to support the growth of forests but also too unpredictable. Periods of drought lasting for months are frequent, and total precipitation, as both rain and snow, may vary significantly from year to year.

Climate is a principal determinant of grassland formation, but other factors-fire and grazing, in particular-are also important. Even after being burned or cropped, grass promptly resumes growth from a zone of tissue protected within a sheath formed by the bases of its leaves. Woody plants are much less resilient in their response to fire and grazing, so even where moisture is sufficient to permit trees to grow, grasses will be favoured.

Grasses predominate in grasslands but they are not the only herbaceous plants to grow there: wild-flowers of many species are abundant, especially in regions that are moist. Trees and shrubs tend to be restricted to the floodplains of streams, or are scattered across the temperate savannahs that form where the more humid grasslands begin to give way to forests.
In the northern hemisphere, major temperate grasslands cover the Great Plains of North America and a belt of similarly flat to rolling terrain in central Eurasia. In the North American grasslands, the climate becomes progressively more arid as one moves from lush tall-grass prairies in the east to prairies covered in short bunch grasses in the west. In Eurasia resemble the tall-grass prairies, but the droughty steppes of Kazakhstan, Mongolia, and northeast China are closer in aspect to North America's short-grass prairies.

The land area that falls within the temperate zone in the southern hemisphere is much smaller than its north-temperate counterpart, and so grasslands of vast extent are lacking. The pampas of Argentina and Uruguay are the largest. Unlike the prairies and steppes, which lie in the interior of their continents, the pampas border the Atlantic Ocean. The climate, nevertheless, is semi-arid, and there is poor drainage due to the extreme flatness of the country, which further encourages the growth of grasses. The remaining southern temperate grassland eco-regions occupy most of the basin of the Murray and Darling rivers in southeastern Australia, some small tracts in New Zealand, and Northern Karoo in South Africa.