Mary Firestone

Professor
Ph.D.  Soil Microbiology    Michigan State University, 1979
  

333 Hilgard Hall
32 Hilgard Hall
Berkeley, California 94720
mkfstone@nature.berkeley.edu
office: 510-642-3677   lab: 510-642-3677   fax:  510-642-6847

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Soil microbial ecology: Microbial processing of carbon and nitrogen underlie the capacity of soil to support plant growth in agriculture, rangeland, forests, and wetlands. However the extreme heterogeneity of soil and the scale at which microorganisms interact with their habitat has made understanding the ecology of soil microbes a challenge of long duration. The research done in the Firestone lab aspires to fundamental understanding as well as knowledge applicable to current problems including terrestrial system response to global change, sustainability, biodegradation, and soil structure. Current research interests include:

• Interactions of bacteria with the soil environment. How does the physical/chemical characteristics of the microhabitat determine growth and activity of soil microbes. Do indigenous soil microbes alter the characteristics of their microhabitats through the production of extracellular polysaccharides matrices? We have learned that:
  • Bacteria indigenous to surface soils are highly adapted (physiologically and ecologically) to soil water potential fluctuations
  • The polysaccharide matrices surrounding bacterial cells in soil control rates of wetting and drying of the bacterial microhabitat
  • Soil water potential and content impact rates of soil microbial processes through diffusional control of solution phase substrate supply as well as control of physiological processes.
  • High amplitude fluctuations in soil redox status in upland wet tropical rain forest soils promote the occurrence of very-low-redox N and C processes.
  • Diffusion-limited mesoscale domains in soil aggregates create habitats for growth and activity of bacteria capable of low redox metabolic processes
• Microbial community ecology of N and C cycling. How does the composition of soil microbial communities control soil N and C transformations including nitrification, denitrification, organic-N mineralization, and production of atmospherically reactive gases. How do differences in the microbial community composition between soils translate into differing soil process rates? We have learned that:
  • The composition of the microbial community (as defined by DNR, RNA and PLFA fingerprinting) can be related to enzyme activity in tropical soils as well as soil C and N transformations in California soils
  • The response of terrestrial ecosystems to environmental change will be determined in part by the impacts of the changing environment on soil microbial communities.
  • The spatial distribution of bacterial communities in aggregates connect redox potential to metal reduction.
• Mechanisms of interaction between plant roots and soil microorganisms. How does the spatially and temporally complex interchange of C and N between plant roots and soil microorganisms control plant-N availability, soil carbon dynamics, and pollutant biodegradation. We have recently earned that:
  • The patterns of exudates along plant roots are spatially complex and differ among small molecular weight compounds. Root patterns control bacterial and protozoal numbers as well as N-dynamics
  • Nitrogen-mineralization is 10x higher in rhizosphere soil and nitrification is controlled primarily by root consumption of ammonium.
  • Root-microbial interactions underlie terrestrial ecosystem response to elevated CO2 and atmospheric N-deposition.
  • Root enhancement of PAH degradation is compound specific, involving selective stimulation of degrading communities by root exudate materials.

Fellow - Soil Science Society of America -1995; Distinguished Scientist, Institute of Ecosystem Studies, NY -1997; Eminent Ecologist, Kellogg Biological Station, MI – 1997; Fellow - American Academy of Microbiology – 2002; Woods Hole Distinguished Scientist in Environmental Science – 2002; Brown & Williams Distinguished Speaker, University of Louisville – 2003; Clark Lecture in Soil Biology, Soil Sci Soc Am - 2004; Distinguished Lecturer in Ecology, University of Wyoming - 2005.

Hawkes, C.V., K. DeAngelis, and M.K. Firestone. 2007. Root interactions with soil microbial communities and processes. In Z. Cardon and J. Whitbeck eds., The Rhizosphere an Ecological Perspective. pp. 1-31. Elsevier, New York.

James I Prosser, Brendan JM Bohannan, Tom P Curtis, Richard J Ellis, Mary K Firestone, Rob P Freckleton, Jessica L Green, Laura E Green, Ken Killham, Jack J Lennon, A Mark Osborn, Martin Solan, Christopher J van der Gast, J Peter W Young. 2007. The Role of Ecological Theory in Microbial Ecology. Nature Microbiology.

Waldrop, M.P. and M.K. Firestone. 2006. Response of Microbial Community Composition and Function to Soil Climate Change. Microbial Ecol. 52:716-724.

Herman, D.H., K. Johnson, E. Schwartz and M.K. Firestone. 2006. Root Influence on Nitrogen Mineralization and Nitrification in Avena barbata Rhizosphere Soil. Soil Sci Soc Am J 70:1504-1511.

Wallenstein, M.D., D.D. Myrold, M. Firestone, and M. Voytek. 2006. Environmental controls on denitrifying communities and denitrification rates: insights from molecular methods. Ecol. Applic. 16:2143-2152.

Waldrop, M.P. and M.K. Firestone. 2006. Seasonal Dynamics of Microbial Community Composition and Function in Oak Canopy and Open Grassland Soils. Microbial Ecol. 52:470-479.

Pett-Ridge, J. and M.K. Firestone. 2005. Redox fluctuation structures microbial community in a wet tropical soil. Appl. Environ. Microbiol. 71:6998-7007.

Hawkes, C., I. Wren, D. Herman, and M. Firestone. 2005. Plant invasion alters nitrogen cycling by modifying the soil nitrifying community. Ecol. Letts. 8:976-985.

Wan, J., T.K. Tokunaga, E. Brodie, Z. Wang, Z. Zheng, D. Herman, T.C. Hazen, M.K. Firestone, and S.R. Sutton. 2005. Reoxidation of Bioreduced Uranium Under Reducing Conditions. Environ. Sci. and Technol. 39:6162-6169.

Balser, T.C. and M.K. Firestone. 2005. Linking microbial community composition and soil processes in a California annual grassland and a mixed-conifer forest. Biogeochem 73:395-415.