Mixed Conifer Forests

Managment Implications

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 experiemtal 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.