Big Bend National Park - USBBP001
Additional Site Information

Helen Poulos, Richard Gatewood, Ann Camp


Dating Method: Crossdated

Sample Storage Location: Greeley Memorial Laboratory, Yale School of Forestry 
and Environmental Studies; Available upon request.

Reference: Camp, A. E., H. M. Poulos, R. Gatewood, J. Karges, and J. Sirotnak. 2006. Assessment of Top Down and Bottom Up Controls on Fire Regimes and Vegetation Abundance and Distribution Patterns in the Southwestern Texas Borderlands: A Hierarchical approach. Final Report to the Joint Fire Sciences Program, Project # 03-3-3-13, October 31, 2006.

Poulos, H. M. 2007. Top down and bottom up influences on fire regimes, diversity, vegetation patterns in the Chihuahuan Desert Dorderlands. PhD dissertation. Yale University, New Haven. 250 pp.

Abstract: Fire history for P. cembroides from the forested uplands of the Chisos Mountains in Big Bend NP. We dated the fire-scar samples by sanding them to a high polish and visually cross-dating them under a binocular microscope using standard dendrochronological techniques (Stokes and Smiley 1968).  Twenty-five of the 31 fire-scar samples we collected were crossdated and used for analysis. The remainder of the samples could not be crossdated and were eliminated from the study. A master chronology for BIBE was obtained from the International Tree-Ring Data Bank (Cook and Montagu 1992) to assist in crossdating. Of the samples collected, 27 were sampled from dead trees (mostly downed logs). We statistically analyzed the fire return intervals in different subcategories or filters. First, we determined the statistical distribution of fire intervals using all fire years, even those represented by only a single scar. Then, we included only those fire years for which 10 or more of the recording samples included a scar. We chose a 10 filter rather than a larger 25 filter based on the limited sample size of fires that scarred 25 of the samples.	
We aged the tree cores and seedling cross-sections by sanding them to a high polish and visually cross dating them under a binocular microscope using standard dendrochronological techniques (Stokes and Smiley 1968). Four hundred fifty tree cores were successfully crossdated and used in the analysis. Additional years to the center were estimated using a pith locator (concentric circles matched to the curvature and density for the inner rings) for cores that missed the pith (Appelquist 1958), We adjusted the tree ages for years lost at coring height using the tree seedling age data by subtracting the number of rings on each destructively sampled seedling at 30 cm from the number of rings at each seedling’s base. The mean number of years lost by the destructively sampled seedlings in each plot was then added to the tree ages for each plot to account for the years of growth missed by coring at DBH.  

Establishment date data from this site are available at:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/firehistory/establishment/northamerica/usbbp001.dat