Variation in chemical and physical properties during leaf development in california bay tree ( Umbellularia californica): Predictions regarding palatability for deer

Abstract

Changes in several chemical and physical characteristics of California Bay Tree, Umbellularia californica, foliage in both new growth and mature leaves were measured from the spring flush (April) until bud set and dormancy in autumn (October). Five sequential leaf developmental stages were described, with leaves passing through Stages One to Four during a growing season, and remaining in Stage Five after winter dormancy (i.e. second year of growth). Monoterpenoid total yield (mg all monoterpenoids/g LDW) increased from very low levels in Stage One to high levels in Stages Four and Five. Monoterpenoid composition (% of total yield by individual compounds) was highly variable among the developmental stages; however, concentrations of the four most abundant compounds, sabinene, 1,8 cineole, pinocarvone and umbellulone, all increased from Stages One to Four. Over winter, the concentrations (mg individual compound/g LOW) of pinocarvone dropped and umbellulone rose dramatically in leaf Stage Five, while the total yield did not change. Total nitrogen content decreased from Stage One to Stage Five. Total nonstructural carbohydrate did not vary statistically among the leaf developmental stages. Leaf specific weight, per cent moisture, and leaf toughness also increased with leaf development. From these results we predict U. californica foliage palatability for Blacktailed Deer.