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How will California’s grassland-shrubland ecotones be affected by a warming climate? Given my interests in plants, water, meteorology (coastal fog!), and vegetation change over time, I approached this broad question through a multifaceted research strategy with a focus on the water relations physiology of Baccharis pilularis (coyote brush, Asteraceae), a common shrub native to California.

1.  Intraspecific variation in water relations of B. pilularis

Despite the fact one is practically guaranteed to see this native shrub when hiking open spaces in the central California coast, there is a dearth of physiological information about it. To help remedy this, I evaluated the intraspecific variation in water relations between the two genetically distinct morphotypes of B. pilularis in a common garden setting in Bodega Marine Reserve (common garden pictured above). These results provided a “baseline” picture of how B. pilularis varies in its responses to fluctuating seasonal water availability.

2.  Effects of ontogeny on B. pilularis seasonal water use and water relations

Plant age influences the way water moves through plants, from annual flowers to tall trees.  I researched how age affects B. pilularis water relations by comparing several parameters of water use in juvenile and adult shrubs in cool, fog-prone and warm, low-fog coastal grasslands. Through seasonal measurements of diurnal water potentials, midday stomatal conductance, tissue water relations characteristics (obtained via pressure-volume curves), and stable isotopes of water sources in young and mature B. pilularis plant tissue, we investigated how life stage affects this species’ ability to respond to differing levels of water deficit.

3.  Seasonal water use and water relations of B. pilularis during seedling establishment in high- and low-fog coastal grasslands

B. pilularis is one of first shrubs to invade grasslands along California’s central coast. Within the context of these landscape dynamics, it is important to understand how young B. pilularis plants use water in the presence of neighboring grassland species, particularly in our changing climate. As such, we conducted a manipulative neighbor removal experiment to measure seasonal B. pilularis water relations, water sources, and plant growth with and without neighbors in warm, low-fog and cool, high-fog coastal grasslands. Results from this study illustrate the responses of B. pilularis seedlings to these different coastal grassland environments and allow us to begin to predict seedling establishment in central California’s coastal grassland-shrubland mosaic.