Alexandra Orrego

Alexandra Orrego

Years participated in RESESS:

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An Overview

Major: Geoscience
Academic Affiliation: Georgia State University
Research Mentor: Brian Harvey
Communications Mentor: Kelly Kochanski


Growing up in the forested areas of North Georgia, Alexandra always maintained an appreciation for the Earth and its environment. During her first year as an undergraduate she realized that her love for the environment could become a career. Since solidifying her studies in Geoscience she is interested in technologies such as GIS, and applying these technologies to investigate changes in the environment that may have hazardous consequences to the Earth, ecology, and humans. She hopes to pursue a graduate degree in environmental engineering. This summer Alexandra analyzed spatial and temporal patterns of accelerating tree mortality rates in subalpine forests located in the Rocky Mountain eco region. Because observed trends of accelerating tree mortality have been identified all around the world, her results will help in forecasting the future of forest ecosystems globally.


Broad Scale Patterns in Subalpine Fir Mortality Across the U.S. Rocky Mountains

Rising concerns about warming climate and trends in increased rates of tree mortality detected in forest ecosystems globally have sparked studies in determining specific causes for tree mortality. This study analyzes spatial and temporal patterns of tree killing agents in the subalpine forests of the Rocky Mountain eco region in order to determine what drivers are causing such accelerated tree mortality events in Subalpine fir trees (ABLA). Although significant research in subalpine forests has been done to addresses pine tree mortality induced by Mountain Pine Beetle outbreaks and spruce tree mortality induced by spruce beetle outbreaks, the third dominant species of subalpine forests, the subalpine fir tree, has received less attention, while its mortality rates have also increased. Thus a spatially expansive study of relationships between pine, spruce, and subalpine fir mortality is necessary to understand overall accelerating tree decline. With the use of United States Forest Service (USFS) aerial detection surveys (ADS) from 1994-2015, we are able to extrapolate presence/absence distribution analyses using Geographic information Systems (GIS) of the forested study area in which we determine likelihood of co-occurrence of subalpine fir mortality (SFM) versus abiotic/biotic factors. A progression from inclusive, exclusive, to focal scale testing allowed us to detect the appropriate spatial scale/extent to produce meaningful ecological correlations of tree mortality drivers in subalpine forests. Counter-intuitively to climate warming effects, areas of significant SFM are occurring in historically cool and wet environments as opposed to forest sites directly exposed to high amounts of heat. With the results of this study we are able to determine interrelated patterns of drivers that may be indirectly/directly inducing tree mortality in subalpine forest, which will help forecast what is imminent in these forest ecosystems.