Baker City Watershed - USBCW001 Additional Site Information Emily K. Heyerdahl, Linda B. Brubaker, James K. Agee Dating Method: Crossdated Related ITRDB Chronology: OR029R, OR030R, OR031R, OR032R, OR034R, OR035R, OR037R, OR038R, OR039R, OR040R, OR041R Sample Storage Location: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ. 85721 Reference: Heyerdahl, E.K., L.B. Brubaker, and J.K. Agee. 2001. Spatial controls of historical fire regimes: a multiscale example from the Interior West, USA. Ecology. 82:660-678 Abstract: Our objective was to infer the controls of spatial variation in historical fire regimes. We reconstructed a multicentury history of fire frequency, size, season, and severity from fire scars and establishment dates of 1426 trees sampled on grids in four watersheds (-64 plots, over -1620 ha each) representative of the Blue Mountains, Oregon and Washington, USA. The influence of regional climate, a top-down control, was inferred from among-watershed variation in fire regimes, while the influence of local topography, a bottom-up control, was inferred from within-watershed variation. Before about 1900, fire regimes varied among and within watersheds, suggesting that both top-down and bottom-up controls were important. At the regional scale, dry forests (dominated by ponderosa pine), burned twice as frequently and earlier in the growing season in southern watersheds than in northern watersheds, consistent with longer and drier fire seasons to the south. Mesic forests (dominated by subalpine fir or grand fir) probably also burned more frequently to the south. At the local scale, fire frequency varied with different parameters of topography in watersheds with steep terrain, but not in the watershed with gentle terrain. Frequency varied with aspect in watersheds where topographic facets are separated by significant barriers to fire spread, but not in watersheds where such facets interfinger without fire barriers. Frequency varied with elevation where elevation and aspect interact to create gradients in snow-cover duration and also where steep talus interrupts fuel continuity. Frequency did not vary with slope within any watershed. The presence of both regional-scale and local-scale variation in the Blue Mountains suggests that top-down and bottom-up controls were both important and acted simultaneously to influence fire regimes in the past. However, an abrupt decline in fire frequency around 1900 was much greater than any regional or local variation in the previous several centuries and indicates that 20th-century fire regimes in these watersheds were dramatically affected by additional controls such as livestock grazing and fire suppression. Our results demonstrate the usefulness of examining spatial variation in historical fire regimes across scales as a means for inferring their controls. Reference: Heyerdahl, E.K. 1997. Spatial and temporal variation in historical fire regimes of the Blue Mountains, Oregon and Washington: the influence of climate. Ph.D. dissertation. Seattle: University of Washington. 224 p. Reference: Heyerdahl, E.K., L.B. Brubaker and J.K. Agee. 2002. Annual and decadal climate forcing of historical fire regimes in the interior Pacific Northwest, USA. The Holocene. 12:597-604. Reference: Heyerdahl, E.K. and S.J. McKay. 2001. Condition of live, fire-scarred ponderosa pine trees, six years after removing partial cross sections. Tree-Ring Research. 57:131-139. Reference: Heyerdahl, E.K. and S.J. McKay. 2008. Condition of live, fire-scarred ponderosa pine eleven years after removing partial cross-sections. Tree-Ring Research. 64:61-64. Establishment data from this site are available at: http://www1.ncdc.noaa.gov/pub/data/paleo/firehistory/establishment/northamerica/usbcw001.dat Comments: We include here only data that is not already available in Heyerdahl (1997). Most of the samples were ponderosa pine, but tree B.10.2 was a western larch, and tree B.3.6.1 was a douglas fir. The plots within the Baker City watershed are numbered as a matrix (row designation followed by column) and the trees within each plot are numbered sequentially beginning with 1. The tree names for these plots include four elemets: "B.R.C.#", where: B represents the Baker City Watershed, R represents the matrix row, C represents the matrix column, and # represents the tree. For example, B.6.10.1 is the first tree sampled from plot 6.10 (row 6, column 10) at the Baker City watershed. However, 11 additional plots were sampled outside the matrix. These plots are numbered sequentially beginning with 1, as are the trees within the plots. The tree names for these plots are consequently made of three elements: "B.P.#", where B represents the Baker City Watershed, P represents the plot, and # represents the tree. For example, B.1.2 is the second tree sampled from plot 1. Composite data for the plots from the Baker City Watershed site are also available via ftp at: http://www1.ncdc.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/supplemental/usbcwplt.fhx 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://www.fhaes.org for more information.