Earth and Planetary Sciences ETDs

Publication Date

Summer 6-14-2022

Abstract

Tree rings contain high-resolution climate proxies of temperature and precipitation (Hughes et al., 1982; Fritts 2012; Scuderi 1993). The objective of this study was to use tree ring cellulose, specifically measuring δ18O - the oxygen-18 to oxygen-16 stable isotope ratio- to investigate the impact of Hurricane Dolores, a tropical cyclone that produced heavy precipitation in the Sierra Nevada in July 2015. Prior studies (Berkelhammer and Stott, 2008, 2009) have shown that conifer forests in California record the influence of varying precipitation regimes in their ring alpha-cellulose. Hurricane Dolores produced an intense precipitation event that inundated parts of the Mojave Desert (Means, 2019) and the southern Sierra Nevada, California (Scuderi 2017). Rainfall from this event fell during the middle of a multi-year drought minimizing potential water sources for plant growth with the exception of Dolores. Radar imagery and soil sensor data record Hurricane Dolores infiltrating and saturating the soil of some sites to below the rooting zone while other sites were unaffected without measurable precipitation. This study investigated whether trees located at inundated sites in the southern Sierra Nevada recorded this extreme Hurricane Dolores precipitation event within their cellulose. It was hypothesized that due to the hurricane’s lighter isotopic values that this event would be recorded as depleted isotopic cellulose values reflecting Dolores’ impact at inundated sites. Alpha-cellulose analysis shows that while the six study areas had varied isotopic responses, no response was indicative of Hurricane Dolores. Potential explanations for this lack of a hurricane signal include the mixing of soil waters, the height of condensation, and more importantly evaporation. The most likely explanation for a lack of isotopic signal within the cellulose is that evaporation during the drought surrounding 2015 enriched available soil water leading to a manifestation of heavier isotopic values within the cellulose record. These intricate relationships altering source water make it difficult to correlate extreme storm events with isotopic values of tree cellulose in California (Bale et al., 2010; de Boer et al., 2019).

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Louis Scuderi

Second Committee Member

Zachary Sharp

Third Committee Member

Matthew Hurteau

Project Sponsors

Geologic Society Of America

Language

English

Keywords

Dendrochronology, Oxygen Isotope, Tree Ring, Sierra Nevada

Document Type

Thesis

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