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A desert is not only a hot, sandy place (as usually people think) but
a desert is any place that does not get much rain. It is an area where
evapotraspiration exceeds
precipitation, for whatever reason.
Evapotraspiration rates will vary, according to
temperature, but less
than 25 centimetres of rain annually will produce a desert in almost any
temperature range. Desert soil is often composed mostly of
sand
and sand dunes may be present. Bottom lands may be
salt-covered flats.
By the point of view of ecology a desert is a
temperate or
tropical
biome characterized by prolonged
drought, generally with extremes in
temperature. As a consequence, deserts have a reputation for supporting
very little life. Compared to wetter regions this may be true, although
upon closer examination, desert are rarely totally without any
vegetation or
fauna but they give more often than not hospitality to few
but highly adapted and specialized plants - like sparse
shrub or
grassland vegetation and animals. Approximately one-third of Earth's land surface is desert.
Most desert plants are drought or
salt-tolerant, such as
xerophytes.
Some store
water in their
leaves, and
stems (succulents) other remains
hidden underground to preserve moisture (geophytes), Other have long
tap
roots that penetrate deeply in the soil to find the
water. Other
grow
and complete their life cycle in a very sort time after an occasional
rain (Ephemeral plants )
Deserts typically have a plant cover that is sparse and desert
vegetation is frequently very complex and divers.
Cold deserts have
grasses and
shrubs as
dominant vegetation. |
