Comparing Climate and Ecological Factors to Identify Growth Releases in Shoshone National Forest, Wyoming

Authors: Brittany Rinaldi*, Radford University, Thomas Callahan*, Radford University, Stockton Maxwell, Radford University, Rebecca Brice, University of Arizona, Karen Heeter, University of Idaho
Topics: Environment
Keywords: Dendrochronology, Climate, Ecological, Wyoming
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Dendrochronology is the study of tree rings to understand past environmental conditions. We conducted a tree-ring analysis at a site in the Absaroka Mountain Range in Wyoming within the Shoshone National Forest. The site was a steep rocky outcrop with trees dispersed across the slope. We collected Douglas fir (Pseudotsuga menziesii) and Engelmann spruce (Picea engelmannii) tree cores to examine climate-growth relationships and growth response to ecological disturbance. Standard tree-ring methods were used in collecting and preparing the Douglas fir and Engelmann spruce samples. The samples were crossdated using standard plotting methods and measured using CooRecorder image analysis software. Then, COFECHA was used to identify measuring and dating errors. The R software packages dplR, treeclim, and TRADER were used to analyze both climate-growth relationships and responses to ecological disturbance. The results from each species were compared to distinguish the cause of growth response to environmental changes. Both species showed positive responses to growing season precipitation and negative responses to growing season temperature. However, some correlations were not stable over time. Engelmann spruce samples showed major growth releases in the 1960 - 1970 period. Another growth release was detected around 1990, possibly a response to the 1988 Yellowstone wildfire. The Douglas Fir samples showed major growth releases in several decades including the 1780s, 1840s, 1860s, and 1990s. Our results showed that both climatic variability and ecological disturbance affected tree growth at our site, indicating that their might be a more complex interaction between climate and ecology driving tree growth.

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