U.S. Water News Online
LAS CRUCES, N.M. -- Getting down to the "root" of studying
how
desert plants can survive for months without rain, U.S. Department of
Agriculture
scientists are using a backhoe to dig 15-foot trenches beneath the
surface of
arid rangeland near Las Cruces. Using ice picks and high-pressure
water
sprays, the researchers are exposing root systems that provide clues
to the
plants' drought defenses.
In determining how some desert plants survive with the scant water
and
searing heat that would kill most other vegetation, "we've seen
plants
equipped with a survival mechanism that overrides the natural
tendency for
plants to send roots downward towards water," said rangeland
scientist Robert
Gibbens of the Agricultural Research Service. "That's good because
roots near
the surface can get moisture from light rainstorms," added
Gibbens.
Desert plants thus can receive moisture from two soil depths, he
noted, "and
this helps explain why shrubs have successfully invaded -- and now
dominate
-- many areas that were once desert grassland." The federal
researchers have
actually found some roots of desert shrubs growing upward, fanning
out to
collect water from rainstorms. Conversely, Gibbens pointed out,
"we've
uncovered mesquite shrubs that have one big root that can grow
downward --
deeper than our trenches -- to tap underground water."
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