DOI: 10.25921/r5kr-0879
title: NOAA/WDS Paleoclimatology - Margolis fire data from Rowe Mesa central, northern New Mexico - IMPD USROW001

description: Pinon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at >2 sites. Tree establishment was negatively correlated with fire frequency (r = -0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean = 881 trees/ha) that is>600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.
description: Description: This site was sampled as part of a project to reconstruct the fire history of the PJ dominated landscape of Rowe Mesa in northern New Mexico. 

Sample_storage_location: University of Arizona Laboratory of Tree-Ring Research, 1215 E Lowell St., Tucson, Arizona, 85721
Dating_method: crossdated
Area_sampled [hectares]: 5.4

FHX File Header: For additional information, see the header of this datasets FHX file, usrow001.fhx, located in the same folder as this file. 

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/ and  https://doi.org/10.5281/zenodo.593323 for more information.