Publication Date

Fall 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Studies

Advisor

Lynne Trulio

Keywords

Climate Change, Coast Live Oak, Elevational Survey, Oak Herbivory, Resource Availability Hypothesis, Santa Clara County

Subject Areas

Environmental management; Botany

Abstract

Climate change is expected to dramatically alter and destabilize critical functions of oak woodlands (Quercus spp.) in California. Oak woodlands support hundreds of vertebrate species and thousands of native insect species. Climate-driven changes in annual temperature, annual rainfall, and spatial climatic variability may increase insect herbivore pressures on mixed coast live oak (Quercus agrifolia) woodlands. The Mt. Hamilton Range of Santa Clara County, California offers a unique matrix to study oak-insect herbivore relationship using elevation as a proxy for climate change. This thesis research assessed the relationship between lepidopteran herbivory and coast live oak with insect surveys and the laboratory analysis of phenolic compound concentrations. Results were evaluated under two plant-herbivore theories, Resource Availability Hypothesis (RAH) and Plant-Size Apparency Hypothesis (PSAH). Results indicate elevation increased as mean annual temperature declined, confirming that elevation in this system is a suitable proxy for climate change. Relationships between herbivory, elevation and plant defense chemicals showed larger plant size correlated with higher herbivory. Overall, the results did not support RAH and partially supported PSAH. Results suggest managers should use alternate hypotheses in combination with an elevational framework. As the climate changes, future elevational surveys may help managers understand how to best preserve Mt. Hamilton’s oak woodlands.

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