PARENT SESSION
Contributed Oral Session 32: Soil Nutrient Dynamics and Acid Deposition
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal

Microbial community succession in unvegetated, recently-deglaciated soils.

Nemergut, Diana ^{*,1, 2}, Schmidt, Steven¹, ¹ University of Colorado, Boulder, CO² Rutgers University, New Brunswick, NJ

ABSTRACT- Primary succession is a fundamental tenet of ecology; however, if and how substrate age controls microbial community composition is poorly understood. We employed molecular phylogenetic techniques to investigate the changes in the bacterial community along a chronosequence of three unvegetated, early successional soils from a receding glacier in Southeastern Peru. We hypothesized that microbial communities would undergo consistent patterns of replacement, and that heterotrophic nitrogen fixers would be abundant in these soils. The phylogenetic diversity of the microbial community was lowest in the youngest soils, and was similar for the intermediate and oldest soils. Interestingly, species richness estimators suggested that the total number of lineages followed a unimodal curve, and was highest in the intermediate age soils. Organisms from the Comamonadaceae group of the Betaproteobacteria, likely heterotrophs that were deposited onto the new soils from within or underneath the glacier, appeared to be dominant in the youngest soils. We also found that Cyanobacteria were abundant in these soils. Although most soil biogeochemical variables showed little change along this ∼20 year soil age gradient, soil N values did increase, perhaps due to the activity of these autotrophic N-fixers. Our results suggest that substrate age, which influences macrobial community structure, may also directly affect microbial community composition.

Key words: soil microbial communities, soil development, microbial succession