Breahna Gillespie

Breahna Gillespie
Ph.D. Candidate, SDSU


San Diego State University
Department of Biology
Physical Sciences, Rm. 240
5500 Campanile Drive
San Diego, CA 92182-4614

Cohort 1 Theme: Water Prediction & Ecosystem Services

Advisor: Walter Oechel 

Expected Graduation: May 2020

Degree: Ecology

Research Title: Comparing a +160-year-old Chaparral Stand Gross Primary Productivity (GPP) to the Net Ecosystem Exchange (NEE) of an Eddy Covariance Tower Across Seasons

Research Synopsis:
Atmospheric carbon emissions have continued to increase, while plants have subsequently removed roughly one-fifth of carbon dioxide. Terrestrial carbon uptake has slowed the rate of CO2 accumulation yet changes in mean temperature and precipitation may negatively impact ecosystems that were previously strong sinks. California chaparral stands in particular potentially could have reduced net productivity from increased drought conditions. This study looks at how the gross primary productivity (GPP) of a stand composed of primarily chamise, redshanks, and desert ceanothus compares to the total net ecosystem exchange (NEE) found with eddy covariance towers. We found that chamise appears to contribute the most to the stands (r = 0.33), compared to the other species. The soil moisture in the stand controls both GPP and NEE while air temperature only shows significance in stand fluxes. Further research is needed to look at all the components of respiration and compare the derived values to the NEE.