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Current and Recent Research Projects

Santa Marguerita Ecological Reserve, black sage in foreground

visit the  SDSU Santa Margarita Ecological Reserve web site

Research in coastal sage scrub (CSS) ecosystems 

The influence of plant functional traits on ecosystem responses to altered rainfall

This is collaboration with Dr. Elsa Cleland at UCSD. We have established a field experiment in which plots dominated by native shrubs or invasive annuals receive three levels of rainfall (50%, 100% and 150% of ambient levels). This work is supported by NSF 1154082.

High and low rainfall treatments

Shrub plotAbove: a shrub-dominated plot being watered.

Left: two weed-dominated plots, one recieving 50% of rain, the other 150%

CSS ecosystems are endangered by human development, disturbance and invasion by exotic plant species. We study how disturbance by fire and invasion in CSS affects microbial communities and the cycling of C, N and water, and how these changes might feed back to influence the plant communities and the ecosystem.  Much of this research has been performed with the cooperation of the Soil Ecology and Restoration Group (SERG) and the laboratories of Douglas Deutschman and Janet Franklin (now at ASU)

LiCor 8100 chambers at SMERRecently graduated Ph.D. student, Marguerite Mauritz (right) used these LiCOR 8100 automated soil chambers to measure controls over soil respiration in plots of annual weeds and native shrubs (See BG discussion article)

Students, Monica Winters and Spring Strahm, at Ranch Jamul

Above: Monica Winters and Spring Strahm. Below: Marguerite Mauritz

Marguerite Mauritz

Native CSS shrubs and exotic grasses differ greatly in their litter chemistry, and their rates of growth, N uptake and transpiration. This can lead to altered biogeochemical cycling and microbial community structure (as was shown greenhouse experiments like this one for Francy El Souki's Masters Thesis)Graduate student, Francy El Souki, with her greenhouse study of native and exotic plants found in CSS Shrub TrimuvirateNative CSS shrubs tend to grow in patches, allowing invasives to colonize gaps. Recently graduated Ph.D. student, Francis Bozzolo (right) studied how different N forms are partitioned among these plants, and how their interactions with the soil microbial community impacts growth of invasive and native plants in CSS (See Plant and Soil Article)

Graduate Student, Francis Bozzolo, records GPS position in Santa Marguerita Ecological Reserve

 

Student, Irene Hale, measures soil respiration at Mission Trails Regional Park

Undergraduate researcher Irene Hale studied soil respiration and microbial biomass in CSS plots varying in invasion and fire history

Sean Doyle

 

We are collaborating with John Kim at the PNWRS to parameterize the dynamic global vegetation model, BIOMAP, for our sudy areas. REU student, Sean Doyle (though shown here at the field site) spent most of his summer in front of a computer helping out on this project.

The role of biological soil crusts in CSS ecosystems

Soil crusts grow in bare patches between shrubs in CSS.  These crusts are held together by polysaccharides produced by cyanobacteria, algae and lichens. We are interested in how biological soil crusts in CSS affect soil microbial communities and processes, and how they might be used for restoration of disturbed areas.

Graduate Student, Tracey McDole, collects crusts

During a rotation in the Lipson lab, Ph.D. student, Tracey McDole (left) used stable isotope probing to trace C flow from the cyanobacteria and algal primary producers into the microbial community, and found that crust photosynthate supports a novel and specialized community of heterotrophic bacteria.

Graduate student, Laura Dane, and assistant collect soil crusts

In her Masters project, Laura Dane found that biological soil crusts in CSS have major impacts on landscape patterns of soil microbial biomass and activity.