DOI: 10.25921/bagj-6266
title: NOAA/WDS Paleoclimatology - Guiterman fire data from Toh-ni-tsa Lookout Road - IMPD USTLR002

description: Isolated, relic populations of Acer grandidentatum (bigtooth maple, Sapindaceae) were found in deep canyons in central Texas. Associated with them on hilltops were communities of Juniperus ashei (ash juniper). We determined the structure of relic A. grandidentatum populations and compared them to adjacent J. ashei populations. The overstory and understory density was counted and basal area was determined for all woody species in both communities using the quadrat procedure. Acer grandidentatum was the highest density (788 ± 964 or 52%) and basal area (29 ± 35 or 52%) overstory species in the canyon communities while J. ashei had the highest density (1589 ± 146 or 92%) and basal area (51 ± 13 or 88%) in the hilltop communities. In the understory of the canyon communities, there were five juvenile tree species including A. grandidentatum which had the fourth highest density (13% or 176 ± 110 plants/ha). In the hilltop communities, J. ashei was the high density understory tree species (52% or 994 ± 400 plants/ha). There were no A. Grandidentatum overstory or understory plants in the hilltop Juniperus communities. Acer grandidentatum had an inverse quadratic size distribution with few juveniles. Although we counted a number of seedlings, there was little recruitment over the last 16 years and very little potential recruitment in the previous 20 years. Juniperus ashei had an inverse exponential size distribution with many understory plants and considerable recruitment. Weibull age/size distributions showed one A. grandidentatum established in the 1670’s and 2 in the 1760’s, with peak establishment in the 1970’s. Causes of the lack of recent recruitment are uncertain, but it could be episodic due to changes in herbivory, management or other environmental conditions.
description: 
Sample Storage Location: Laboratory of Tree-Ring, University of Arizona
Dating Method: Dated
Related ITRDB_Chronology: Not Applicable

Fire scar data from this site are available in FHX2 format at:
  https://www.ncei.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/ustlr002.fhx
along with associated metadata, including links to supplemental information files and Fire History Graphs, at:
  https://www.ncei.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/ustlr002-noaa.txt

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 https://www.fhaes.org/ for more information.