Climate Signals in California Western Junipers (Juniperus occidentalis) from Quantitative Wood Anatomy
By: Jonathan Pressley
Department: Earth & Climate Science
Faculty Advisor: Dr. Alexander Stine
Measurements of the year-to-year variability in tree-ring width have been a rich source of information about environmental conditions before the instrumental records. However, it hasn’t proven easy to extract climate signals from ring width in some of the longest-lived tree species. Here we explore the feasibility of using dendroanatomical methods to identify climate signals in long-lived western juniper (Juniperus occidentalis) trees. We examine how climate affects western juniper cell size and cell wall thickness in the Sierra Nevada to determine how cell anatomy measurements might be used to produce more accurate climate reconstructions in California. Of particular interest is the relationship between pseudo-density and ambient temperature, as it has been difficult to constrain annual temperature variation before 1849 for most of the region. Our laboratory has developed an automated digital camera system that captures thousands of macro images of an ultra-finely sanded tree core sample, enabling us to analyze cellular, and anatomical structures within the ring structure and throughout the core. Anatomical components are then measured using high-resolution composite images. This work focuses on characterizing cell anatomy/climate relationships at two sites between 2000- and 2800-meters elevation in the Central California Sierra Nevada.