Document: KER-3-57-5

The relationship between land use history, soil characteristics and microbial community structure along a gradient of increasing intensity of disturbance.

STEENWERTH, K.L.* ¹, F.J.CALDERÓN ², L.E.JACKSON ¹, K.M.SCOW ¹ and M.R.STROMBERG ³

University of California at Davis, Davis, CA 95616 USA ¹
Universidad de Puerto Rico, Rio Piedras, Puerto Rico 00926 ²
University of California at Berkeley, Berkeley, CA 94720 USA ³

Abstract:
We surveyed sites in the Central Coastal region of California with different land use histories along a gradient of increasing intensity of disturbance for soil characteristics and microbial community structure as described by phospholipid ester-linked fatty acid (PLFA) analysis. Sites were limited to sandy textured soils derived from granitic parent material and shared similar particle size distribution. Measured soil characteristics were pH, total soil carbon and nitrogen, moisture content, exchangeable cations and particle size. Total PLFA per site represented a measure of microbial biomass. Management variables included use of fertilizer, pesticide and irrigation, presence of grazing, plant type and cover, time since tillage, aspect and slope. Landscape categories were based on current land utilization and included intensively managed irrigated and rainfed cropping systems, old fields out of cultivation for 10-70 years that support introduced annual grasslands, and relict stands of native perennial grassland. Multivariate statistics showed that all three factors had important roles in distinguishing sites with different landscape categories. Soil characteristics, PLFA and management variables explained 55-65% of the variation among sites, when each factor was analyzed independently of the others. When all three factors were combined, discreet clusters of sites of similar landscape categories emerged. The most important factor determining clustering was PLFA profiles. Thus, a given landscape category can be identified by a distinct soil microbial community structure as well as similar soil characteristics and management variables.

Keywords: microbial community structure, phospholipid ester-linked fatty acid (PLFA), land use history, granitic soil, microbes

This abstract is being presented at: 3:30 PM in session:
MICROBIAL ECOLOGY