Ashenfelder Upper - USASU001
Additional Site Information

Peter M. Brown


Dating Method: Crossdated

Reference: Brown, P.M., Ryan, M.G., and T.G. Andrews. 2000. Historical 
Surface Fire Frequency in Ponderosa Pine Stands in Research Natural Areas,
Central Rocky Mountains and Black Hills, USA

Brown, P.M., and W.D. Shepperd. 2001. Fire history and fire climatology 
along a 5° gradient in latitude in Colorado and Wyoming, USA. 
Palaeobotanist 50:133-140.

Abtract: (Brown, Ryan, and Adrews, 2000) "Historical range of
variability" and "reference conditions" are two concepts that attempt
to characterize ecosystem conditions as they may exist in the absence
of pervasive human impacts. However, to define reference conditions from
reference landscapes, such as U.S. Forest Service Research Natural Areas,
requires a long-term perspective by which to assess whether existing
ecosystem conditions are driven by predominately natural rather than
human factors. We used fire-scarred trees to reconstruct centuries-long
chronologies of surface fires in four research natural areas (three
established and one proposed) that contain ponderosa pine (Pinus ponderosa
Laws.) forests in South Dakota, Wyoming, and Colorado. Fire frequency
was variable among research natural areas, but recent fire-free periods
in three of the four areas were up to approximately 2.5 times longer
than any presettlement intervals. Loss of surface fires most likely is
related indirectly to recent land and resource use in areas outside of
the research natural areas and related directly to fire suppression and
livestock grazing in the research natural areas themselves. Studies that
attempt to define reference conditions for ponderosa pine ecosystems from
existing conditions in these Research Natural Areas will need to consider
changes that may have occurred in these areas as the result of loss of
historical fire patterns. Determination of historical fire frequency also
should provide useful information for the management or restoration of
ecosystem processes and conditions in these or similar natural areas.

Comments: The "." and "|" symbols were not used in the standard manner as
described in the FHX2 users manual, in that they do not indicate whether or 
not a year is considered a "recorder" year. Rather, the "|" symbol is used 
to indicate that a dated ring was present, while the "." symbol is used
to indicate that no dated ring was present (typically before and after the
age range of the tree as well as between an estimated pith date and the 
earliest ring that was present). 

Fire History Graphs: Fire History Graphs illustrate specific years when 
fires occurred and how many trees were scarred. They are available in both 
PDF and PNG formats. The graphs consist of 2 parts, both of which show the 
X axis (time line) at the bottom with the earliest year of information on 
the left and the latest on the right.
The Fire Index Plot is the topmost plot, and shows two variables: sample 
depth (the number of recording trees in each year) as a blue line along 
the left Y axis, compared with the percent trees scarred shown as gray bars 
along the right Y axis.
Below, the Fire Chronology Plot consists of horizontal lines representing
injuries by year on individual sampled trees. Symbols are overlain that 
denote the years containing the dendrochronologically-dated fire scars or
injuries. The sample ID of each tree is displayed to the right of each
line. The Composite Axis below represents the composite information from
all individual series. The symbols used to represent the fire scars or
injuries, and the filters used to determine the composite information,
are shown in the legend.
These graphs were created using the Fire History Analysis and Exploration
System (FHAES). See http://frames.nbii.gov/fhaes/ for more information.