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Scrublands in North America are a vast open area of perennial grasses, armored
plants and a variety of shrubs. Most of the worlds scrublands have one thing
in common, they normally grow where water is scarce for several months each year.
Scrublands are not always dry. Although some scrublands receive less than
8" of rain a year, it is unevenly spread, and a lot of rain might arrive within
a short time. Meanwhile, the rest of the year might be endlessly dry.
The unevenness of the rainfall makes it hard for trees to survive. Low-laying
scrubland plants like heather, sage, evergreen oak and a variety of cactus dominate
these areas. Trees in a scrubland rarely grow to great heights due to the dryness
of the soil. A usually tall oak will rarely grow over 6' tall and will usually
show prickly leaves.
A savannah is a grassland with scattered scrubs and isolated trees. Savannas
are always found in warm climates where annual rainfall is about 10-30 inches.
The soil of savanna is porous, with rapid drainage of water. It has a thin
layer of humus, which provides vegetation with nutrients. Savannas are sometimes
classified as forests. The predominant vegetation consists of grasses and
forbs. Different savannas support different grasses and plants due to amounts
of rainfall and soil conditions, but all savannas are highly specialized to grow
vegetation that can withstand long periods of drought. Savannas have both
and rainy and dry season, and can be found between a tropical rainforest and a desert
biome. Savannas are also known as tropical grasslands.
GRASSLANDS (sometimes called prairies)
Grasslands grow where this is not enough rain for forests to develop, but too
much rain for a desert. Grasslands generally show an abundance of perennial
grasses such as buffalo grass, purple needlegrass, blue grama and many others. Wild
flowers such as blue sage, bluebonnet, red paintbrush, cactus, coneflowers,
asters, sunflowers cover most of it's surfaces. The soil of most grasslands is too
thin and dry for trees to survive. However, a few trees such as cottonwoods,
oaks and willows will survive. Temperate grasslands have hot summers and cold
winters. Rainfall averages about 10-30" per year.
There are two types of rainforests, tropical and temperate. Tropical rainforests
are found close to the equator. Temperate rainforests are found along coasts
in the temperate zones, such as the Pacific Northwest of the United States.
Both share certain characteristics, it has a continuous average rainfall of approximately
100" per year, flowing water, acid soils, most trees flare at the base, vegetation
is dense, tall and very green and adapted for the shade. Both types of rainforests
are rich in epiphytes and mosses with a great amount of course woody debris. However,
the diversity is greater in the tropical rainforest. Tropical rainforests are warm
and moist, while temperate rainforest are cool and moist.