Biology ETDs

Publication Date

Spring 5-16-2026

Abstract

Isotopic compositions of plants from the past provides empirical evidence for paleoclimatic shifts and plants physiologically response. This study used Neotoma paleomiddens (fossilized debris piles) collected from Death Valley National Park, which contained preserved abundant plant materials. These middens range from modern to >35,000 years and capture different climatic events in Earth history. Employing Juniperus osteosperma (Utah Juniper) leaves found in middens, I investigated variation in carbon and nitrogen stable isotopic composition. To help interpret paleomidden results, we used modern field and herbaria samples of Juniperus from a spatial gradient stretching across their geographic range. Results showed δ 13C was remarkably consistent over time, whereas δ 15N revealed significant enrichment towards the present. Surprisingly, modern Juniperus leaves showed no correlation with weather variables leading to speculation that space and time substitutions are not useful for interpreting long-term climate trends. We suspect the nitrogen stable isotope enrichment may reflect increasing aridity.

Keywords

Stable isotopes, paleomiddens, juniper, paleoclimate

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Dr. Felisa Smith

Second Committee Member

Dr. Scott Collins

Third Committee Member

Dr. Hannah Marx

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