Left Hand Canyon - USLEF001 Additional Site Information Peter M. Brown Dating Method: Crossdated Reference: 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. Abstract: We reconstructed fire chronologies covering the past four to six centuries from fire scars recorded in tree-ring series from 18 sites in the central Rocky Mountains of Colorado and Wyoming. Sites are located in forests containing predominately Pinus ponderosa. Median fire-free intervals in fire chronologies are related to latitude, with shorter intervals in southern stands than those in the north. However, strength of this relationship varied through time, with a stronger latitudinal gradient in fire frequency from 1600 to 1800 than from 1700 to 1900. Variability in fire frequency with time may be related to strength of regional climate gradients. Seasonality of fire scars also varied across the latitudinal gradient, from predominately early season fires in the south to late season fires in the north. Superposed epoch analysis of fire years with annual variability in Palmer drought severity indices shows that fire years throughout the gradient were dry, but those in the south were preceded by wet years. This result suggests that fuel amounts may have been limiting in southern forests where fire intervals were shorter, and that longer intervals in the north permitted fuel buildup between fires. All chronologies show a general cessation of fire scars beginning in the latter nineteenth century, coincident with widespread Euro-American settlement of the western US. 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.