Using Quantitative Wood Anatomy to Improve Tree-Ring Reconstructions of Climate and Environmental Disturbances

Author

Savannah Anne Collins-KeyFollow

Date of Award

8-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Geography

Major Professor

Sally P. Horn, Matthew F. Bekker

Committee Members

Nicholas N. Nagle, Monica Papes

Abstract

Quantitative wood anatomy (QWA) provides an avenue for dendrochronologists to investigate wood samples at the cellular level to quantify distinctive features formed in the xylem, which can serve as proxies for past environmental conditions. This dissertation research explores the use of QWA to improve the identification of signals from past climate and environmental disturbances in trees rings. Another objective of this dissertation research is to show how QWA methods can be more accessible to more dendrochronologists. At three distinct sites, I collected core samples from overcup oak, eastern hemlock, and whitebark pine, and used dendrochronological methods to construct chronologies. QWA then was employed to measure and count continuous and discrete anatomical features within each of the tree-ring samples, and these parameters were examined for indicators of climate and environmental disturbances. First, I constructed chronologies of multiple anatomical features in overcup oak from the Lower Pearl River in southeastern Louisiana and compared each chronology to known spring flood records. I determined three of these anatomical features are correlated to major and moderate spring floods, and I potentially detected two major undocumented spring floods. Next, I examined the frequencies of anatomical anomalies in eastern hemlock from Great Smoky Mountains National Park in Tennessee for indications of insect infestation, and investigated a possible decoupling of climate and tree growth responses post-infestation. I found QWA helped us better detect anatomical anomalies, but only intra-annual density fluctuations appeared to increase post-infestation, and tree growth became less temperature-dependent post-infestation. Finally, I compared anatomical features in living versus dead whitebark pine from the Beartooth Mountains of Wyoming, then compared those features to extreme environmental events. I observed that anatomical values are higher in living trees, and responses of features to extreme events suggest that dead trees experienced enhanced water stress that could have weakened their defenses leading to higher mortality. Additionally, I constructed a ‘blue’-ring chronology from the whitebark pine that reflects volcanic eruptions and ephemeral cold events over the 20^th century. These three studies show how wood anatomical analysis can be applied to dendrochronological problems and how it can inform future studies.

Recommended Citation

Collins-Key, Savannah Anne, "Using Quantitative Wood Anatomy to Improve Tree-Ring Reconstructions of Climate and Environmental Disturbances. " PhD diss., University of Tennessee, 2023.
https://trace.tennessee.edu/utk_graddiss/8708