Current
How does coastal fog impact crop water use in a California agricultural system?
Coastal fog, a low stratus cloud that intercepts land, offsets water stress in a variety of ecosystems during the dry season in Mediterranean climates. In coastal California, the occurrence of summertime fog overlaps with the peak growing and harvest season for many economically important crops. In an effort to inform irrigation decisions in an ultimately water limited ecosystem, I conducted field investigations to understand the impact of coastal fog on crop water use in strawberry fields in the Salinas Valley, California from May-October in 2015 and 2016. Specifically, I quantified the effects of foggy and non-foggy conditions on leaf and canopy-scale gas exchange rates (e.g., photosynthesis, transpiration, and stomatal conductance). I also installed passive fog collectors and micrometeorological instrumentation to measure the effects of fog on the physical environment. In 2016, I collaborated with biometeorologist, Dr. Andrew Oliphant in the Department of Geography & Environment at SFSU, to collect continuous observations of how local meteorology, and fog events in particular, impact the energy, water, and carbon fluxes at the field scale using an eddy covariance approach. The results from this work will be presented at the AGU Fall Meeting in December 2016.
Other Projects
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How does coastal fog influence the physiology and distribution of a drought-sensitive pine species?
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In my dissertation research, I investigated how coastal fog influences the water relations and distribution of Bishop pine (Pinus muricata D. Don), a drought sensitive species restricted to the fog belt of coastal California and offshore islands. I conducted three related projects motivated by the following research questions: 1) What are the spatial patterns and environmental drivers of drought-induced Bishop pine mortality at the southern extent of its distribution in California on Santa Cruz Island? 2) What are the effects of summertime drought and fog water inputs on the water relations of adult and sapling Bishop pines, and 3) How do fog-drip and canopy fog immersion impact leaf-level physiological function during a dry-down period? The outcomes of these studies provide evidence that coastal fog is an essential element to augmenting plant available water during the dry season and that its occurrence supports the southern extent of its range on Santa Cruz Island. Moreover, this work advances our ability to make mechanistically-based predictions of how foggy coastal forests may respond to a warmer, drier climate.
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How does variation in water availability and use differ between trees and shrubs during drought?
There is widespread concern that changes in climate may lead to vegetation change across California, which, in turn, would impact watershed hydrology. To generate mechanistically-based projections of how potential type conversion from forested to shrub dominated systems may affect streamflow, we addressed the following question: How does variation in water availability and use differ between trees and shrubs during seasonal drought at a snow-rain transition zone in the Sierra Nevada? As a postdoctoral researcher on this project, I led field investigations at two sites in the southern Sierra Nevada that are part of the Critical Zone Observatory network (SSCZO) to quantify plant water availability at the rooting zone, plant stress, and instantaneous leaf-level function from April - October in 2014, which was also during the historic drought in California. A key finding from this work is that shrubs have a less conservative water use strategy than do trees and maintain higher rates of photosynthesis even as soil water deficit increases during the seasonal drought during one of the driest years on record. The results from this work have important implications for land-use management decisions, specifically whether or not to manipulate plant communities in an effort to manage water resources.
Impact of historic drought on the age and size structure of a fog-influenced coastal forest
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The mega drought of 2014 in California offered an opportunity to address fundamental questions about the controls on population dynamics and the local distribution of a drought-sensitive coastal pine species, Bishop pine. Anecdotal evidence supports the idea that tree mortality may also be density-dependent because areas of high mortality are also where die-back has occurred in the past and where there is a more even-aged stand structure. Ecophysiological data on this species indicates that the water status of sapling Bishop pines declines more rapidly through the seasonal dry period compared to adult trees. Based on the outcome of these studies, it is reasonable to hypothesize that severe drought will have detrimental effects on the population dynamics of Bishop pines. I led a team of postdoctoral, graduate, and undergraduate students with Dr. Christopher J. Still from the Department of Forest Ecology & Society at Oregon State University to quantify the effect of extreme drought on Bishop pine population structure and function. The results from this study show that the 2014 was the primary cause of drought-induced mortality across tree age classes. Overall, this study provides a baseline assessment of how severe drought impacts coastal forest population dynamics, which is critical for making predictions of how the persistence of this species may be impacted by drought events in the future. The results from this study were presented at the Ecological Society of America Meeting in August 2015 and will be the subject of a talk I will give at the Northern California Botanist Meeting in January 2017.
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