Desert Ironwood The desert
ironwood only grows in the washes and valleys of
the Sonoran
Desert
below 2,500 foot elevation. The Sonoran Desert is
located in southwestern Arizona, southern
California, and the northwestern part of Mexico.
The Sonoran desert is known as a hot, dry desert.
The vegetation is mostly desert scrub. The
boundaries of the ironwood's habitat and that of
the Sonoran desert are almost the same. Desert
ironwoods are usually found in sandy washes where
water is available. The desert ironwood,
or palo fierro in Spanish, provides desert plants and
animals with the food and shelter they need to survive. Its
importance comes from the part it plays in the survival of
over 500 plants and animals in the Sonoran Desert. As the
desert ironwood grows, it alters the environment around
itself, and creates a micro-habitat. Its dense canopy shades
the ground under it, bringing temperatures down at least
15° F. Its seeds provide food for many doves, quail,
and small rodents. Insects thrive in the ironwood canopy,
which also attracts birds and reptiles. They make their home
under and in the ironwood, providing prey for
cactus
owls, hawks
and coyotes.
Its nitrogen-fixing
nodules on the root system, and nutrient-rich leaf
litter fertilizes the soil around it. Native bees
pollinate the ironwood flowers, which are also used
as medicine. The
ironwood is known as a "nurse plant". It provides a
safe place for seed germination, and protects
seedlings from extreme cold. It also protects
saplings from the damaging effects of the sun.
Thorny, low-hanging branches shelter young
saguaro
and organ pipe cacti, night-blooming cereus, and
other desert plants from browsing animals. Many
wild flowers grow under the desert ironwoods, which
are eaten by jack
rabbits,
desert
bighorn sheep,
Sonoran
pronghorns,
and mule deer. As many as 230 plant species have
been recorded growing under the
ironwoods. The bark on young branches is gray and smooth. Older bark becomes wrinkled and creased, eventually shredding on older trunks. It has leathery, compound, pinnate leaves about 2 inches long with 6 to 9 leaflets about .75 inches long. The leaves are covered with fine hairs. A pair of thorns about .5 inch long grows at the base of each leaf. During the dry season the ironwoods will drop their leaves to conserve water. They never drop all of their leaves, so their canopy provides protection from frost and high heat all year round. They bloom
from April to June just before the new leaves grow
back. Clusters of pea-like flowers ranging from
pink, pale-rose, to white, grow in archs at the end
of branches. These develop into brown, bean-like
seedpods about 2 inches long. Each seedpod has 1 to
4 brown beans in it. The ironwood seeds mature at a
time of year when very few plants are producing
fruit. Wildlife is highly dependent on its seeds.
The seeds can also be roasted and eaten, or ground
into a flour. When given
enough water the desert The wood of the desert ironwood is very hard and dense. It actually sinks in water. It was used by the Seri Native Americans of Mexico for tool handles. Today the Seri Indians make carvings of desert plants and animals from the ironwood. Dead wood is gathered from the desert floor, and the carvings are made with hand tools. Tradition has it that carvings made from the desert ironwood bring good fortune and long life. The carvings are in much demand, especially large carvings, and bring in a lot of money. Illegal harvesting of ironwood is on the rise and live trees are being cut down. Desert ironwood burns very hot and is used to make charcoal. Woodcutting causes an average of 17% reduction in ironwood. Wood has been illegally cut even in the Organ Pipe Cactus National Monument and other protected areas. Desert ironwood trees grow only in the Sonoran desert. Urban developments are threatening their habitat. Many of Tucson, Arizona's housing developments are expanding into the ironwood forests. The destruction of the forests means the destruction of the special ecosystem the ironwoods create. The already endangered cactus pygmy owl, which depends on the ironwoods for it prey, would be in greater danger of extinction. The threatened desert bighorns and Sonoran pronghorn antelopes depend on it for forage. It would mean the disappearance of the saguaro and the pipe organ cacti which need the shade of the ironwoods when they are young. Although it doesn't look like a very important tree, in the desert the ironwood tree enables life to flourish. Without it, that life would disappear. 2002
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