Plateau - USPLT001
Additional Site Information

Henri D. Grissino-Mayer, William H. Romme, M. Lisa Floyd-Hanna, David Hanna


Dating Method: Crossdated

Sample Storage Location: Laboratory of Tree-Ring Research, The University of 
Arizona, Tucson, AZ.

Reference: Henri D. Grissino-Mayer, William H. Romme, M. Lisa Floyd-Hanna, 
and David Hanna, 2003, in press. Climatic and human influences on fire 
regimes of the southern San Juan Mountains, Colorado, USA. Ecology.

Abstract: Fire severity, frequency, and extent are expected to change 
dramatically in coming decades in response to changing climatic conditions, 
superimposed on the adverse cumulative effects of various human-related 
disturbances on ecosystems during the past 100 yrs. To better gauge 
these expected changes, knowledge of climatic and human influences on 
past fire regimes is essential. We characterized the temporal and 
spatial properties of fire regimes in ponderosa pine forests of the 
southern San Juan Mountains of southwestern Colorado by collecting 175 
fire-scarred tree samples from nine sites across a wide range of 
topographic settings. All tree rings and fire scars were dated using 
standard dendrochronological techniques. Fire-free intervals were 
statistically modeled using the Weibull distribution to provide 
quantitative measures that characterized the historical range of 
variation,in,pre-Euroamerican fire regimes.

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.