Mixed conifer forests cover 0.4 million acres in Arizona. Relatively
little herbaceous vegetation is produced under dense overstories in these
forests. As a consequence, carrying capacities for livestock and wildlife,
which graze these forests in summer, are low in relation to other vegetative
types in the region. Mixed conifer forests contain: water, timber, forage,
recreation opportunities (camping, hunting, picnicking, hiking, and site-seeing),
and habitats for a variety of big and small game animals, rodents, and
game and non-game birds.
Annual precipitation (above 9,500 ft ranges from 30 to 45 inches) is
usually in excess of potential evapotranspiration. As a result, streams
originating in this area are often perennial. Stream originating in low
elevation mixed conifer forest (8,000 to 9,500 ft) are mostly intermittent.
Snowmelt runoff is a significant source of annual runoff.
Research results from the experimental watersheds in the White Mountains
of Arizona have increased the knowledge about hydrology and watershed
management of mixed conifer and high elevation ponderosa pine forest in
the Central Arizona Highlands, and to some extent, of the high elevation
grasslands. Watershed treatments were directed toward practical options
that would be useful to forest managers. This is demonstrated by:
The shift in opening size, from large openings dominated with seeded
grasses on the North Fork of Workman Creek (Rich
and Gottfried 1976), to smaller 20 acre openings on Castle Creek
where tree regeneration was the goal. The small 1 to 2 acre openings
on the South Fork of Thomas Creek were the next step in achieving forest
regeneration while increasing runoff by increasing snow accumulations
and lowering evapotranspiration demands. The shift in size also reflects
concerns about forest esthetics. The change from even-aged to uneven-aged
siliviculture in the residual stands also reflects this change.
The initial emphasis of the watershed management research program
was to determine how to increase runoff into the Salt River System.
Management for other forest resources, especially timber and wildlife,
was of secondary importance in the 1950s. However, management for water
at the expense of the forest was unacceptable.
Water-yield augmentation is no longer a primary management goal in
the Central Arizona Highlands. Even timber production has declined as
other forest values, such as recreation and concerns about rare and
endangered species, have increased.