Final Report\*

October 2001

**Fire History Reconstructions in the Mogollon Province Ponderosa Pine
Forests of the Tonto National Forest**

**Central Arizona**

J. Mark Kaib (<mark_kaib@fws.gov>)

U.S. Fish and Wildlife Service

Region 2, 500 Gold Ave. SW

PO BOX 1306

Albuquerque, NM 87103

\* Full Report on File at Tonto National Forest and the Laboratory of
Tree-Ring Research, University of Arizona

**Abstract---** Four montane-conifer forest sites were selected for fire
reconstruction studies in central Arizona within the Mogollon Biotic
Province. The sites include Webber Creek (West of the Dude Fire), Mount
Ord, the Pinal Mountains, and the Sierra Anchas. Fire history was
reconstructed from fire-scarred pine samples using tree-ring-dating
methods (dendrochronology) and analyzed in the context of land-use
history. Presettlement fire regimes were reconstructed and the relative
extent of past fires inferred.

Fire regimes declined precipitously at all sites with Anglo-American
settlement, livestock grazing, and logging beginning in the early 1880s
(Fig. 1). Presettlement fire frequencies were relatively high and
extremely variable at all sites. A fire-regime shift to fewer
finer-scale with more frequent medium- and broader- scale fire events
was recorded for the century after 1780 at Webber Creek and Mount Ord.
Large numbers of fine-scale fire events were recorded at MFIs ranging
between one to two years. These fires roughly ranged from one-hundredth
to one hundred hectares.

Presettlement fire history reconstructions indicate that ponderosa pine
and mixed-conifer forest stands below the Mogollon Rim experienced
fine-, medium-, or broad- scale fire events at least every other year.
The high frequency and spatial variability of fire regimes at these
sites indicate the profound role that fires had in the past in shaping
the landscape patterns throughout this province.

**Introduction**

Fires have been an important ecological process for hundreds and
thousands of years in the pine forests of central Arizona (Weaver 1964,
1968; Wright and Bailey 1982; Dieterich 1983a; Anderson 1993). Fire
history studies in the Mogollon Biotic Province have been conducted in
western New Mexico (Swetnam 1983; Dieterich and Swetnam 1995; Abolt
1997), northeast of these study areas (Dieterich 1980b; Dieterich and
Hibbert 1988), and to the southeast (Grissino-Mayer et al. 1995). The
most relevant fire history research has been recently completed in the
montane-conifer forests of the San Carlos Apache Tribe to the east (Kaib
2001).

**Tonto National Forest Land-Use and Fire History**

The Tonto Apache inhabited and farmed the upper Webber Creek study area
around the late 1800s (Northern Gila County Historical Society 1984;
Redman 1993). Substantial land-use changes began in this region with the
Apache settlement on reservations (Johnson 1970; Sheridan 1995). In the
1880s settlement period, Pine Arizona became a Mormon colony and
ranching homesteads increased rapidly. The early communities subsisted
primarily on livestock ranching supplemented with hunting, trapping,
logging, and farming (Gosney 1899; Croxen 1926; Forrest 1936; Ellison
1968). There were several sawmills established around the 1880s in Pine,
Payson, and Christopher Creek (Northern Gila County Historical Society
1984). The settlement period between 1880 and 1890 marks the beginning
of tremendous land-use and vegetation changes throughout the Southwest
U.S., and the Mogollon Province was no exception (Hastings and Turner
1965; Bahre 1991; Sowards 1997).

Historical records illustrate early settlement land uses and vegetation
changes.

William Craig settled the Spade Ranch within the study site area on
Webber Creek in 1883. He recounts the forest character in the vicinity.

> "Pine bunch grass in the pine timber under the rim was three feet high
> and stood in great bunches. The cattle and horses that grazed it ate
> only the heads (Croxen 1926: 3)."

The Haught family settled and developed some large ranch herds in this
area.

"Sam Jr. \[Haught\] came to the upper Webber Creek in 1882 and brought a
fine herd of cattle with him... The herd grew to near 10,000 head and
Sam Jr. had nearly 1,000 horses \[by ca. 1898\] (Nellie Gene Connolly;
Northern Gila County Historical Society 1984: 118)."

A surveyor for the General Lands Office describes the forest changes in
central Arizona that had occurred by the turn of the century.

> "Briefly, the history of the forests of Arizona, which my
> opportunities have enabled me to gather from many of the oldest
> reliable pioneers, is that when first invaded by the white man the
> forests were open, devoid of undergrowth, and consisted in the main of
> matured trees, with practically no forest cover. Instead of forest
> undergrowth, the ground was well set with perennial grasses and other
> herbage... Where hundreds of tons of hay were cut under the actual
> spread of the forest trees... there is not now enough grass on a
> thousand acres to keep in condition a family cow. Where were then
> running streams are now dry arroyos, and where were then living
> springs are now beds of silt and sand (Holsinger 1902: 22-23)."

Fred Croxen (1926) estimated that there were 15 to 20 times more cattle
in 1900 compared to 1926. It was approximated from his and other USFS
records that in the year 1900 about one and a half to two million cattle
were grazing in the Tonto N.F., compared to the 26,400 cattle permits
that existed in 1993 (Alford 1993). The effects of intense grazing in
the decades between 1880 and 1910 were also compounded by repeated
droughts (Bahre 1991). The influence of early settlement grazing and
logging on fire suppression has been well documented early on and at
most fire history sites throughout the Southwest U.S. (Leopold 1924;
Marshall 1963; Swetnam and Baisan 1996a, 1996b).

![](media/image1.wmf)**Figure 1.** Fire history chronology chart showing
crossdated fire-scarred trees (horizontal lines) with dated fire events
(vertical hatchmarks), and fire composites below showing fire events
recorded by increasing numbers of trees (≤10% fire-scarred trees, ≥10%
fire-scarred trees, ≥30% fire-scarred trees), that indicate increasing
relatively-larger fire events. Note severe decline in frequent fire
regime in late 1800s.

# Lightning and Fires

The role and importance of lightning as a source of fire was greatly
underestimated in this region until the establishment of USFS fire
guards and lookouts (Plummer 1912; Barrows 1978; Swetnam and Baisan
1996a; Allen 2000). This historical bias taints earlier historical
accounts of human-set fires that were not witnessed firsthand. The
Mogollon region was demarcated in 1912 as a lightning "hotspot" based on
surveys of lightning-scarred trees (Plummer 1912). U.S. Forest Service
records over 14 years show that 81 percent of the fires recorded in the
Southwest Region (New Mexico and Arizona) were attributed to lightning
(Barrows 1978). In this Region between 1940 and 1975, an average of
1,770 lightning fires occurred annually. Furthermore, forest fuel and
fire conditions were probably very different in presettlement times
compared to current high densities of living, dead, heavy, and fine
fuels (Cooper 1960; Weaver 1951; Fule et al. 1997). The greater grass
cover and more open forests where fuels could dry out more quickly may
have facilitated even higher rates of lightning ignition and fire spread
in the past.

Settlement land uses and particularly grazing fragmented these
landscapes and reduced the grasses and forbs thereby preventing normal
fire ignitions and spread (See Fig. 1). The last widespread
presettlement-like fire was recorded at Webber Creek in 1886, even
though seven fire-scarred tree samples extended well beyond the 1950s.
The last widespread fire at Mount Ord was recorded in 1881, suggesting
an even earlier influence from grazing. The last widespread
presettlement-like fire in the Pinals was recorded in 1889 and the last
widespread fire in the Sierra Anchas was recorded in 1890. All these
sites had tree samples that extended into the current decade; however
widespread-fire events were not recorded over the last century (See Fig.
1).

**Fire, Fuels, and Climate Changes**

Although there were probably some fires that went unrecorded by the
trees sampled at these sites over the last 100 years, the frequency and
size of fires have been severely reduced (Bahre 1991; Thiel 1993;
Sowards 1997). USFS Region-3 fire records in Arizona and New Mexico also
show that major changes in fire regimes have occurred over the last
century (Fig 2; Grissino-Mayer and Swetnam 2000). These records indicate
that on average less than 500,000 hectares burned annually in Region-3
between 1910 and 1970, and there was a steady increase in the annual
area burned after 1970 that peaked at over 2.5 million hectares in 1994
(See Figure 2; Grissino-Mayer and Swetnam 2000).

In northern Arizona, Fule and others (1997) found ponderosa pine forest
densities in 1883 had 65 trees per hectare with a mean diameter of 42
centimeters, compared to 720 trees in 1994 with a mean diameter of 23
centimeters. These and other authors have concluded that an ecological
shift from low-intensity surface fires to anomalous stand-replacing
fires is partly due to a century or more of fire suppression and
accumulated forest biomass (Swetnam 1990; Fule et al. 1997). The
Southwest U.S. warming-drying trend that began in the 1990s likely has
exacerbated this shift to stand-replacing fires. The majority of
firefighters and incident managers on the Dude Fire had not in their
careers witnessed Southwest ponderosa-pine stand-replacing fires of this
magnitude before this event.

![](media/image2.wmf){width="5.05625in" height="4.252083333333333in"}

**Figure 2.** Annual Area burned on Federal, State and Private lands,
1919-1996. Note increase in hectares burned in Southwest U.S. beginning
in the 1970s (Swetnam et al. 2001).

**Management Implications**

The severe reduction in the numbers and extent of fires over the last
120 years has resulted in much denser forest stands and fuel conditions,
and increased the likelihood for anomalous stand-replacement type fires
(Cooper 1960; Weaver 1964; Fule et al. 1997). The unprecedented Dude
Creek, Four Peaks, and the Coon Creek fires have recently demonstrated
these types of anomalous fire intensities on the Tonto N.F..

There have been hundreds of thousands of acres consumed by anomalous
stand-replacing fires in ponderosa pine forests of the southwest since
the Dude Fire (e.g., Rattlesnake, Aspen, Cerro Grande, Rodeo Chediski,
etc...).

The high frequency and spatial variability of fire regimes at these
sites indicate the fundamental role that fires had in the past in
shaping the landscape patterns throughout this province. This natural
range of variability may ironically facilitate the future use of fire in
ecosystem management by providing greater flexibility to the application
of fire in the ponderosa pine and mixed-conifer forests of the Southwest
US.