Managing Semi-Arid Watersheds: Watershed Basics - Fire and Its Role in the Watershed
Fire has been a part of the natural ecosystem
since the origin of vegetation on earth. Historically, fires have occurred
as often as every 2 years to as infrequently as 400 years in most North
American plant communities. In Arizona, natural fires in ponderosa pine
communities occurred historically every 4 to 12 years. Fires eliminated
young pines and other conifer species, and kept the forest open and park
like. Fire is responsible for plant distribution and varied vegetative communities.
Overall, fires are beneficial because they reduce fuel buildup (for example
the Yellowstone Park fire of 1987), reduce dense understories of shrub and
trees, and increase plant and wildlife diversity.
Throughout the world, chaparral is thought to be a fire-induced vegetation
type. In fact, some chapparal species germinate from seed after a fire.
In Arizona, burned chaparral areas that are left to recover naturally
can survive for 80 to 100 years. In general, fire helps to keep chaparral
communities diverse and productive as long as they do not occur more frequently
than 20 to 30 years apart.
Fire has been a dominant force controlling the distribution of juniper,
but fire is not the only factor. Fire, drought, competition, and effects
of grazing play a role in the distribution of juniper. Prescribed burning
is a management technique that has been used in the Beaver Creek Watershed.
Fire is not a cure-all for all forest and range management problems.
Poor rangeland condition cannot be improved with fire alone. Rangelands
in poor condition must first be restored using other reclamation techniques.
However, once the rangeland is in good condition, fire can be used as
an effective management tool in special situations during wet weather
cycles to control undesirable species such as burroweed, broom snakeweed,
creosote bush, cactus species, and young mesquite trees. Desirable species
such as native grasses may increase. Fire is effective and inexpensive
for many land management problems, if used by people skilled in the use
of prescribed burning.
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