Effects of Management, Soil Attributes and Region on Soil Microbial Communities in Vineyards (Napa, California, USA)

Soil microorganisms play an important role in soil health. However, little is known about the relationship between soil microbial community composition and diversity and commercially significant aspects of soil health. The purpose of this study is to: (1) assess the impact of management practices on both biotic and abiotic soil characteristics in winegrape vineyard soils in Napa Valley, CA, and (2) identify which soil features mediate shifts in bacterial community structure. Bacterial community composition was estimated using a culture-independent analysis of 16S rRNA gene sequencing data. Non-metric multidimensional scaling and permutational multivariate analysis of variance of the weighted UniFrac distance matrix showed that the bacterial communities clustered as a function of tillage and cover crop type. In addition, the bacterial communities are patterned along gradients of soil chemical properties, i.e. pH and pools of carbon and nitrogen, and by soil type (US Soil Taxonomy) and region (American Viticultural Area). The results presented here establish a framework for future research in: (1) understanding microbial roles in soil quality, (2) using DNA fingerprinting for soil health assessment and maintenance in perennial cropping systems, and (3) investigating soil microbial community composition as a potential factor in influencing wine terroir.