Location and SettingThe Centennial Forest is 19,114 ha of State Trust
Land located in northern Arizona. Approximately half, 9,012 ha, of the Forest is
located to the southwest of Flagstaff in a checkerboard pattern interspersed
primarily with the Coconino National Forest.
The second half, 10,102 ha, is located north of Flagstaff, to the west of
Wupatki National Monument in a contiguous block. The Centennial Forest is close
to two major travel routes - Interstate 40, and Highway 89. Portions of the
forest are within a 10 minute drive from Northern Arizona University.
Landforms and GeologyMost of the region encompassed by the Centennial
Forest is composed of geologically young volcanoes and lava flows known as the
San Francisco Volcanic Field. Volcanic activity has shifted from the southwest
portion of the Centennial Forest to the northeast portion over the past six
million years. Consequently, volcanic soil parent materials range from several
million years old in the southwest to less than 70,000 years old in the north.
The hilly, cratered landscape formed by this volcanism rests upon an elevated
sedimentary plateau that marks the southern boundary of the Colorado Plateau
region. Small outcrops of the plateau's sandstones and limestones occur
throughout the Centennial Forest.
ClimateThe climate within the Centennial Forest is affected primarily
by elevation. In general, precipitation increases and temperatures decrease
along a 600 m elevational gradient from the northeast (lowest elevation, 1700 m)
to the southwest (highest elevation, 2300 m). However, climate varies
significantly from year to year. For example, the length of the growing season
in the Flagstaff area averages 115 days, but has been as long as 177 days and as
short as 73 days. Precipitation follows a bimodal distribution. Snow is
concentrated during the winter months of December through March. The summer
months of July to October receive precipitation from often heavy monsoon driven
thunder storms. The entire northern portion of the Centennial Forest receives
greater than 50% of its precipitation during the summer precipitation period
whereas the southwest portion of the Centennial Forest receives greater than 50%
of its precipitation during the winter months. Mean annual precipitation
increases from approximately 28-36 cm in the northern grassland portion of the
forest to 60-68 cm in the ponderosa pine forests southwest of Flagstaff.
VegetationGeology, geomorphology and climate differences help form a
diverse array of vegetation in the Centennial Forest. Regional forest and
grassland vegetation types are well represented throughout the forest.
Vegetation in the northern portion of the Centennial Forest can be classified
into four major terrestrial ecosystems and several minor ecosystem classes.
These ecosystems, described by potential climax vegetation include approximately
5,000 ha of grasslands (Bouteloua gracilis, Elymus elymoides, Aristida
longiseta, and Agropyron smithii), 5,300 ha of pinyon-juniper (Pinus edulis,
Juniperus monosperma) woodlands, and transition zone forests (J. monosperma-P.
ponderosa). The southwest portion of the forest is dominated by extensive (7,200
ha) Pinus ponderosa and P. ponderosa-Quercus gambelii forests. Another 425 ha
are composed of vegetation types that include Juniperus deppeana, and Fallugin
paradoxa as indicator species. In addition to forests and grasslands, the
Centennial Forest contains over 1,200 ha of wetland-meadow ecosystems. Carex,
Poa, Festuca, Agropyron, Allium, and Muhlenbergia species typify these
environments. Minor vegetation types include Quercus turbinella-Arctostaphylos
pungens shrublands which represent a transition zone into upland Sonoran Desert,
and Populus tremuloides-Pseudotsuga menziesii forests which transition into
mixed-conifer vegetation. Throughout the Centennial Forest, transitional zones
between these diverse vegetation types and along elevational gradients are
particularly well represented.
Land Use HistoryCentennial Forest natural resources were first
exploited by Native American inhabitants several thousand years ago. Evidence of
ephemeral use of resources can be found throughout the Forest in the form of
hunting and gathering artifacts, and temporary shelters. However, two sections
of the Forest contain evidence of permanent settlement including significant
archeological resources such as petroglyphs and pueblos. Euro-American
settlement in the late 1800s brought timber harvesting and domestic livestock to
the region. Since settlement of the region occurred relatively recently, timber
and grazing records are available for the entire duration of Euro-American
settlement. Logging activity touched much of the southwestern portion of the
forest, but several areas were uncut or only lightly affected by logging. Some
of the best examples of ancient ponderosa pine forests remaining in the
Southwest occur on the Centennial Forest.
ManagementThe Centennial Forest is designated as a research and
teaching laboratory and administered by the Arizona State Land Department and
Northern Arizona University School of Forestry. Under current management
guidelines, considerable flexibility exists to manage lands to achieve broad
research and educational objectives. Since the Centennial Forest opperates under
a single managerial plan, there exists the possibility to create and study truly
landscape level ecological phenomenon.
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Scientific Description 
