Garth Ornelas

Garth Ornelas

Years participated in RESESS:

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An Overview

Major: Physics
Academic Affiliation: Southwestern University
Research Mentor: Thomas Veblen
Communications Mentor: Keith Jennings


Garth is a recent graduate from Southwestern University in Georgetown Texas with a degree in physics. Upon seeing the detrimental effects of forest fires close to the Austin and Boulder areas, he has discovered an interest in the study of fire dynamics, especially in close proximity to domesticated areas. He will be entering a master's program in fire protection engineering at California Polytechnic State University in the fall.


Updating Tree Ring Width Chronologies of Engelmann Spruce in Subalpine Forests of Colorado's Front Range

The effects of climate change on forests throughout the western United States have manifested in different ways including the outbreak of bark beetle infestations (Bentz 2010) and an increase in forest fire susceptibility caused by warming temperatures and drought in certain areas (Westerling et al. 2006; Sherriff et al. 2014).  We explore the direct correlations among climate variability and radial tree growth in recent years. We accomplish this by creating a tree ring chronology for a xeric and a mesic site on Niwot Ridge and then comparing the chronologies to past measurements taken in the 1980s by Villalba et al. (1994).

We looked for trees used to compile the past chronology and then cored samples from each site using an increment borer.  The samples were then mounted, sanded, and measured.  From these measurements we created stand-level chronologies and compared the trends to climate data in the area.

Comparison of these newly created tree-ring chronologies with the published chronologies based on sampling conducted in the 1980s indicates that the new chronologies were accurately created.  Based on the new chronologies extending through 2015, we discovered that at both a xeric and a mesic site radial growth is negatively correlated (i.e. growth is reduced) during warmer years and especially when the growing season one year prior to the formation of the annual ring is warmer.  The negative influence of warmer growing season temperatures on tree growth appears to be greater at the xeric site than at the mesic site.   Overall, these results imply that warming temperatures are likely to have a negative influence on tree growth rates in these high elevation stands.