PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 4 - Soil, mycorrhizal, and microbial ecology
Exhibit Hall, Ballroom Level, Cook Convention Center

Microbial community composition and diversity during 90,000 years of habitat development in soil chronosequences.

Williams, Mark^*,1, Tarlera, Silvana², Ivester, Andrew ³, Whitman, William⁴, ¹ Mississippi State University, MS State, MS² Universidad de la República-Uruguay, Montevideo, URUGUAY³ University of West Georgia, Carollton, GA⁴ University of Georgia, Athens, GA

ABSTRACT- Soils are known to contain "species" richness that are unrivaled by any other terrestrial system. We hypothesize that the factors accounting for much of this biological richness are related to the existence of a complex network of micro-niches characterized by various types of soil minerals, organic matter chemistries, and the age of the soil. The central goal of this work is to study how microbial community composition, diversity, richness, and structure change as function of soil development, and whether these changes occur in a predictable or succession-like process. Studies are being conducted using 5 soil chronosequences formed from eolian dunes on the Georgia Coastal Plain that range in deposition and developmental age from 1 to 100,000 y BP. In this presentation, we focus on bacterial community composition that is associated with the zone of clay accumulation (Bw/Bt horizons; 20- 40cm depth). Chronosequences were chosen because they represent soils that are genetically very similar and are millennia-scale controlled experiments that differ primarily as a result of differences in time as a soil-forming factor. We have collected data on soil depositional and organic C age through the techniques of optically-stimulated luminescence and 14C- radiocarbon analysis, respectively. Particle size composition, organic matter content, and bacterial 16S rDNA clone libraries (100 sequences) were then measured to begin a preliminary analysis of the relationship between stage of soil weathering and bacterial community composition. Clone library sequences are in the process of analysis. The data indicate that there were significant differences in the composition of the bacterial communities between the soil chronosequences. As well, soil developmental age was strongly related to increasing prokaryotic richness. Based on 80% sequence similarity with type strains, 20-60% of the soil chronosequence ribotypes were not present in the Ribosome Database Project.

Key words: soil bacterial diversity, habitat genesis, 16S rDNA clone libraries