Monday, November 5, 2007
96-16
Soil and Geographic Controls on Prokaryotic Community Composition and Diversity.
Himaya Parilla Mula and Mark A. Williams. Plant and Soil Sciences, Mississippi State University, Rm 117 Dorman Hall, Stone Bldvd, MSU, MS State, MS 39762
The diversity of bacteria in soil is staggeringly large, yet the factors that regulate the development of community composition, diversity and richness remain largely unknown. Because of the profound way that prokaryotes shape the soil and global biogeochemical cycles of carbon and nutrients, a better understanding of the patterns of species abundance in soils can shed light on the links between community composition and function. We discovered in a previous study of soil B-horizons, that soil development in an aeolian chronosequence of five soils between 5,000 and 77,000 y was associated with increasing richness and diversity of bacterial communities. We wanted to confirm this trend in the A-horizon and compare bacteria community composition and diversity differences associated with differences in the horizon-related microbial habitat. We thus compared the bacterial communities at two soil depths by constructing the 16 rRNA clone libraries from the A horizon of soils with ages of 4,000, 45,000 and 77,000 y and compared them to their B horizon counterparts. Libshuff analysis, a statistical tool that determines whether the two libraries are different, showed significant difference (P=0.02) between prokaryotic communities in the A and B horizons across soil ages. Similar to what was previously observed from the B horizons, bacterial communities of the A horizons differed significantly with soil development. We will further examine the nature of the differences between the bacterial communities within the soil horizons and across soil developmental ages.