Vegetation Classification and Mapping Project Report - USGS

Introduction
plateau country of the ‘four-corners’
area of the Colorado Plateau, is located
east of Holbrook in northeastern
Arizona. The park is hourglass-shaped
and approximately 40 km (24 mi) long
(fig. 1). Topographic relief within the
park is not extreme (1620 m to 1890 m,
or around 5,273 ft to 6,152 ft), with the
major elevation changes occurring where
various mesas within the park drop to
surrounding plateau lands. The Puerco
River bisects the park at the midpoint (fig.
2). Interstate 40 intersects the park in the
northern section. The Petrified Forest
Road runs the length of the park and
connects the northern park headquarters
and the southern park museum. Two areas
at PEFO, approximately 50% of the park,
are designated wilderness: a northern
wilderness unit located in the Painted
Desert and a southern unit located in the
Rainbow Forest area (Thomas et al. 2006).
The project area includes the entire park
and a buffer (park environs) of 1 km
(0.6 mi). These park environs include
lands owned by private cattle ranchers,
state lands with cattle allotments, and
Navajo Nation tribal lands, and consist
of approximately 15,144 ha (about 37,421
ac). The entire study area is 53,201 ha or
around 131,463 ac.
1.5.1 Park Establishment
Theodore Roosevelt established Petrified
Forest National Park as a national
monument in 1906. His Presidential
Proclamation (34 Stat. 3266) states:
“. . . whereas, the mineralized
remains of Mesozoic forests,
commonly known as the ‘Petrified
Forest’ . . . are among the greatest
of scientific interest and value and
it appears that the public good
would be promoted by preserving
these deposits . . . with as much
land as may be necessary for proper
protection thereof.”
The park contains one of the largest
concentrations of petrified wood in the
world, as well as abundant plant and
animal fossils from the 225 million yearold
Chinle Formation (NPS 2004, Thomas
et al. 2006). Subsequent proclamations
and acts of Congress expanded the park
to include cultural as well as natural
resources. PEFO gained national park
status in 1962 (72 Stat. 69) and portions
of the park (20,340 ha or 52,070 ac) were
designated as wilderness in 1970 (84
Stat. 1105). The boundaries of the park
now encompass a variety of significant
natural and cultural resources, including
some of the most valuable and accessible
paleontological resources in the world
(NPS 2004).
1.5.2 Pre-park History
According to the most reliable
information, human occupation of the
Southwest began after the end of the
Pleistocene, about 10,000-15,000 years ago
(Cordell 1997). The earliest inhabitants
of the southwestern region, called
Paleo-Indians, hunted large animals like
mammoth and bison and left evidence
of their presence in the form of hearths,
tools, and sometimes bones at kill and
butchering sites. Although no campsites
or bone concentrations have been found,
Folsom-style projectile points with their
distinctive, fluted (grooved) form have
been found in the park, suggesting that the
areas that are now park lands were at least
occasionally occupied during this period
(Thomas et al. 2003).
During the decline and extinction of the
Pleistocene megafauna after around 10,000
BC, people most likely relied increasingly
on plant resources for survival. During the
Archaic period, from about 6000 BC to
around 300 AD, plant resources probably
became an increasingly important part
of the subsistence base in the Southwest.
Sometime around 1000 BC, people in
what is now the southwestern region of
the United States became more sedentary
and began to cultivate domesticated plant
species (Cordell 1997). Crop plants like
corn and squash developed in Mexico.
During the time of the Archaic culture,
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