The purpose of this study was to continue the characterization of soil microbial communities in Pinot Noir vineyard soils by comparing the variability in microbial community composition over time in a specific vineyard relative to the variability in composition across many vineyards. The study also aimed to show the effect that vineyard management has on the diversity of soil microbial communities, by comparing a vineyard microbial community to an adjacent microbial community under a different land use on the same soil type.
A set of soil samples was collected from nine Pinot Noir vineyards in Anderson Valley, Russian River Valley and Los Carneros in June of 2000. These samples were analyzed for microbial community biomass and composition using phospholipid fatty acid (PLFA) analysis. In June of 1998, the microbial biomass in the soils ranged from 14 to 107 nanomoles per gram soil, as compared with a range of 11 to 85 in June of 2000. There was a substantial drop in microbial biomass in all vineyard soils between 1998 and 2000. The total number of fatty acids detected ranged from 38 to 58 for both years. Despite differences in biomass, the differences in community composition between the two years were small and usually less than differences between vineyards. Although some samples from within a particular region were similar to one another, overall there was still not a strong relationship between wine region and a particular kind of microbial community. A set of paired vineyard and adjacent land use sites are currently being identified with the help of growers.