Do Functional Traits Differ in Chaparral and Coastal Sage Scrub Populations of Black Sage?

HARBESON 26

Coastal sage scrub and chaparral are adapted to Southern California's Mediterranean Climate with its characteristic summer drought. A number of species co-occur in chaparral and coastal sage scrub including Salvia mellifera, black sage. We examined several functional traits in a chaparral population and a coastal sage scrub population of black sage. Chaparral individuals were collected from the San Gabriel Mountains in San Gabriel Canyon, and coastal sage scrub individuals were collected at the Arroyo Pescadero trailhead in the Whittier Hills. We measured leaf area to mass ratio (SLA), proportion of spongy mesophyll in leaf cross sections, and hydraulic conductivity which is the capacity to move water through stems. We predicted higher water availability for chaparral individuals would result in increased SLA, a greater proportion of spongy mesophyll leaf tissue, and higher hydraulic conductivity relative to coastal sage scrub individuals. Lower SLA enables plants to limit water loss, and spongy mesophyll may increase water loss when stomata are open. The ability to move increased amounts of water through stems from roots to leaves is a disadvantage when water is less available because of increased risk of embolisms blocking water carrying conduits. Chaparral individuals had significantly greater hydraulic conductivity and a greater proportion of spongy mesophyll, but SLA was higher in chaparral individuals because of greater leaf mass. The results of this project enable us to understand how individuals of a species adapt to changing water availability and temperature regimes, and may shed light on how species can adapt to climate change.