Hidden Valley South - USHV2001 Additional Site Information Rosemary L. Sherriff, Thomas T. Veblen, and Jason S. Sibold Dating Method: Crossdated Sample Storage Location: Biogeography Lab, Department of Geography, University of Colorado, Boulder, CO, USA Reference: R.L. Sherriff, T.T. Veblen and J.S. Sibold. 2001. Fire history in high elevation subalpine forests in the Colorado Front Range. Écoscience 8 (3):369-380. Abstract: Resource managers rely on knowledge of fire history to guide management decisions, but for the subalpine zone of the Colorado Front Range little information exists on fire history documenting changes in fire regimes over the past several centuries. We examined fire history at 13 high elevation sites in the Colorado Front Range to detect long- term trends that may be related to changes in land use and/or climate variability. There is a high degree of spatial and temporal variation in fire regimes across sites; however, most sites exhibit an increase in fire frequency during the 20th century compared to the 19th century. We did not find any evidence that fire suppression after the creation of National Forests and Rocky Mountain National Park in the early 1900s decreased fire frequency at the highest elevations of forest cover in the Front Range. Human influences over the last 200 years have played less of a role in these high elevation subalpine forests than in the lower elevation forests of the Colorado Front Range. In the absence of effective fire exclusion in these high elevation forests, there is no basis for assuming that forest structure and fuel conditions are outside of the historic range of variability for this habitat. Fire occurrence in these high elevation sites is highly dependent on drought, which often results from La Niña events. In comparison with lower elevation ponderosa pine forests of the Front Range, fire is less dependent on increased fuel production following wet El Niño events. Comments: bracketed fire-scar dates - sample no. HS308, HS303, HS306, HS302, HS310, HS307, HS301, HS304 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.