PARENT SESSION
Oral Session # 68: Soil Ecology I: Communities, Respiration, and Nutrient Cycling.
Presiding: C Rumbaitis-del Rio
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 106.
The influence of plant diversity and land-use on the diversity and function of soil nitrifiers.
Carney, Karen*,1, Bohannan, Brendan1, Matson, Pamela1, 1 Stanford University, Stanford, CA, USA
ABSTRACT- Soil microbial communities mediate many critical ecosystem processes. Little is known, however, about the factors that determine microbial community composition, and whether community composition influences process rates. Using an experimental site at La Selva Biological Station, Costa Rica, we are examining whether plant diversity and community composition and land-use alter soil microbial communities, and whether microbial community differences can influence transformations of carbon and nitrogen in soils. Nitrification, the transformation of ammonium to nitrate, is a critical step in the nitrogen cycle and is performed by relatively few microorganisms, the ammonia oxidizers. We examined the molecular composition and diversity of autotrophic ammonia oxidizers in soils from plots with varying levels of plant diversity and across land-use types. Ammonia oxidizers, characterized by PCR amplification, cloning, and sequencing of 16S rDNA with group-specific primers, differed across the different land use types. Using a laboratory assay that controls for factors other than the microbial community composition known to influence this process, we also found that nitrification potential significantly varied across the plant diversity gradient and between land-use types. We tested whether the differences in ammonia oxidizer community were related to differences in nitrification rates; preliminary results suggest that differences in nitrification rates may be more related to changes in the overall abundance of soil microbes than to their composition.
Key words: nutrient cycling, microbes, diversity, land-use