Submitted to: World Congress of Soil Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2006
Publication Date: 8/1/2006
Citation: Steenwerth, K.L., Parker, S., Kluepfel, D.A., Lambert, J., Smart, D.R. 2006. Effects of grapevine roots, soil resources and depth on soil microbial communities in a pinot noir vineyard. World Congress of Soil Science.
Technical Abstract: Soil microbial communities are influenced by many factors, including root presence, soil disturbance, variation in soil type and texture, and gradients in resource availability. We investigated the relationship between these factors and the associated soil microbial communities under Pinot Noir grapevines in the Carneros region of Napa County, Ca. Soil pits were excavated adjacent to grapevines at three slope positions: shoulder, mid-slope and toe-slope. Three transects containing all slope positions were sampled, for a total of nine soil pits. Samples for soil microbial community composition were collected from rhizosphere and bulk soil in four horizons and were described by phospholipid fatty acids (PLFA).In order to compare several methods for describing soil diversity, soil samples from one transect were cultured on S1 media to select for Pseudomonas spp. and TBSA media to select for a wider array of isolates. These isolates were identified by fatty acid methyl esters (FAME) and 16SrDNA analyses. Soil characteristics were measured in the bulk samples, including bulk density, total carbon (C) and nitrogen (N), exchangeable cations and cation exchange capacity, texture (i.e., sand, silt and clay), and gravimetric water content. Depth was the significant factor in determining the segregation of soil microbial communities. Decreases in soil C and N and increases in soil bulk density were highly correlated with increasing depth and tended to explain the differentiation of soil microbial communities with depth. Results from this study suggest that soil microbial communities change with depth due to shifts in soil C content and attributes associated with soil morphology despite root presence and variation in slope position.