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Microbial Ecology of Agricultural and Wildland Soils

Our broad interest in microbial community ecology and understanding what determines the composition of a particular soil community has led to numerous projects and collaborations. In collaboration with Chuck Ingels, we have studied the effect of cover crops on vineyard soil microbial communities and we conducted a 3-yr project for the American Vineyard Foundation on soil microbial communities in Pinot Noir vineyards of Napa, Sonoma and the Alexander Valleys. We have collaborated with April Boulton (influence of ants on soil communities), Kerri Steenwerth (microbial communities along a disturbance gradient), and Vic Claussen (restoration of serpentine soils). We have investigated the responses of microbial communities and their processes (denitrification and respiration) to tillage in a collaborative project with Louise Jackson (Dept. of Vegetable Crops) and Dennis Rolston (funded by USDA NRI, USDA SARE) which has led to several publications (Calderon et al., 2000; Calderon et al., 2000).We have also collaborated on studies of how management practices affect soil communities with farm advisors Bruce Roberts (cotton) and Roger Duncan (peach and almonds).

We are involved in research on sustainable agriculture in two large collaborative projects, the Sustainable Agriculture Farming Systems (SAFS) project, a long term, collaborative study begun in 1988, and the Long Term Research in Agricultural Systems (LTRAS) project. The objectives of these projects are to compare conventional, organic, and low input management systems through measurement of soil fertility, biology and structure; crop productivity and quality; pest and disease incidence; and economic performance. Previous research from our involvement includes work on wet-dry cycles and cover crop incorporation, and current work is focusing on emerging questions related to tillage, water management, biodiversity, and carbon sequestration (Gunapala et al., 1998; Lundquist et al., 1999a, 1999b, 1999c).

We collaborate on research projects investigating the interrelationships between microbial communities (particularly methanotrophs) and gas fluxes in rice cultivation. One project has been in collaboration with Jim Hill and Glenn Fitzergerald (Fitzgerald et al., 2000) and another with Stan Tyler at UC Irvine (Macalady et al. pubs).

A new project concerns the development and application of quantitative PCR methods for detecting Salmonella in agricultural soils with the goal of understanding their survival in the soil environment.