PS 29-163 - Assessing recent drought response in northern New Mexico with respect to overstory tree mortality in the ponderosa pine ecosystem

Tuesday, August 9, 2011
Exhibit Hall 3, Austin Convention Center
Sean Casey Dugan1, Brian P. Oswald1, Randy G. Balice2 and Daniel R. Unger3, (1)Arthur Temple College of Forestry and Agriculture, Stephen F. Austin State University, Nacogdoches, TX, (2)Emergency Operations, Los Alamos National Laboratory, Los Alamos, NM, (3)Arthur Temple College of Forestry and Agriculture, Stephen F. Austin State University

A prolonged contracted La Niña event coincided with a prolonged period of below-normal precipitation and above-normal temperatures from 1998-2002 over an extensive swath of the Northern Hemisphere.  This event created stressful living conditions for many plant species around the world, especially in the American Southwest.  The result of these climatic stresses was a significant tree dieback in many of the wooded areas in the southwestern United States.  This is of interest because tree dieback not only changes the physical structure of the stands but also can potentially change the fire regime.  It should also be noted that many of these areas have been subject to over a hundred years of fire suppression which has left many stands overstocked with trees.  The objective of this study is to evaluate and quantify the difference in tree mortality before and after the recent drought in the ponderosa pine ecotone.  The region of interest is in the eastern portions of the Jemez Mountains and the adjacent Pajarito Plateau in northern New Mexico.  The majority of the study area is in Los Alamos County, New Mexico. 


Percent mortalities were taken yearly and grouped into pre and post-drought categories. Two-sample one-tailed t tests and Wilcoxon paired-sample one-tailed t tests were used to determine if there were any significant increases in tree mortality with respect to drought response.  Very significant differences have been observed in the preliminary results with some P values being <0.0005.  We have observed that ponderosa pine, while being characteristically drought tolerant, was highly affected by the recent drought.  This mortality data will also be paired with meteorological data in order to determine why this particular drought was so damaging to the ponderosa pine ecosystem.  The results from this study will allow managers to better forecast drought response in the future.

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