Alexander Chacon, University of California Santa Cruz
Project: Comparing the Water-Use Strategies of Two Coastal Mediterranean Trees
Advisor: Jarmila Pitterman
Two co-occurring tree species, Arbutus menziesii and Quercus agrifolia, were monitored over the course of a dry season to compare different strategies of water usage during seasonal drought. Water potentials and stomatal conductance were taken hourly from pre-dawn to sunset for two sets of measurements per species, and mid-day measurements were taken every week through the dry season. Quercus had lower mid-day water potentials for most of the summer than Arbutus, with some degree of overlap. Arbutus consistently had a higher stomatal conductance than Quercus through the dry season. Vulnerability Curves for both species were made, with Arbutus having a much more negative P50 than Quercus. Throughout the summer, Quercus had been operating near its P50 while Arbutus remained significantly above its P50. Predawn water potentials for Arbutus became higher in mid-summer than early summer, suggesting it may be relying on deep groundwater, and Quercus has been regulating water loss through low stomatal conductance.