Resource and Stress Interactions in Regulating Microbial Communities in a California Grassland Soil

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Resource and Stress Interactions in Regulating Microbial Communities in a California Grassland Soil Patricia A. HoldenUniversity of California-Santa BarbaraFrom surface to groundwater, soil is rich in microbes that perform many functions essential to the entire planet. In the past, soil microbes have mostly been studied by sampling the surface where nutrients from plants abound yet microbes experience extremes of moisture and temperature. Comparatively less studied are soil microbes at depth where moisture and temperature stresses are reduced, but microbes are more starved for nutrients. How do the counteracting pressures of water stress and nutrition affect the makeup and function of soil microbes throughout a depth profile? In this project, soils along a well-studied depth profile at the UC Sedgwick Natural Reserve will be sampled and moisture plus carbon nutrition will be manipulated in the laboratory. Sensitive DNA-based techniques will be used to discover how microbes change with changing nutrition and how nutrition facilitates survival when soils are dry. Stable isotopic (13C) forms of carbon substrates will be traced through microbial populations to discover which microbial groups are most actively processing nutrients. This research is important because, while society depends on soil microbes to recycle nutrients and biodegrade pollutants, how surface and deep soil microbes function is only weakly understood. The knowledge gained from this research will help in understanding such broad concerns as pollutant fates and consequences of global warming. To educate others about the importance of deep soil microbes, an interpretive display will be constructed at the research field site where adult groups and K-12 students tour with docents through an existing educational visitation program.