After a comprehensive study of plants across theU.S., researchers have
concluded that plants able to fix atmospheric nitrogenare most diverse
in arid regions of the country, which runs counter to the prevailing
assumption that nitrogen-fixers, are comparatively most diverse in
environments where soil nitrogen is limited.

Plants incorporate nitrogen into nearly every structure and reaction
that takes place in their cells. Without nitrogen, plants are unable to
produce proteins, create enzymes, or even photosynthesize. Plants have
repeatedly evolved innovative ways to get as much nitrogen as they can
from their surroundings. While soil lacks nitrogen, there is an endless
supply hanging just out of reach as nitrogen gas makes up about 78
percent of Earth's atmosphere. However, plants are not capable of
absorbing it. Bacteria, on the other hand, have mastered nitrogen
fixationand botanists have speculated for decades that plants harboring
these bacteria should be more diverse in ecosystems like savannas and
grasslands.

To determine which environmental factors played the biggest role in
shaping nitrogen-fixing plant communities in the U.S., researchers from
the Florida Museum of Natural History, Louisiana State University, and
Mississippi State University analyzed records for both native and
invasive species from more than 40 sites across the U.S., including
Puerto Rico. They found that the number of nitrogen-fixers increased in
nitrogen-poor environments and decreased in progressively drier areas.
The researchers also looked at the diversity of native nitrogen-fixers
and found that the diversity of native nitrogen-fixers sharply increased
in arid regions, regardless of the amount of nitrogen in the soil.

Plants that pull nitrogen from thin air thrive in arid environments â??
Florida Museum Science (ufl.edu)
[www.floridamuseum.ufl.edu]