PARENT SESSION
Oral Session #25: Soil Ecology: Microbial and Invertebrate. Presiding: W. Parsons.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.
Impact of soil nutrient availability on microbial community composition in Hawaiian tropical soils.
BALSER , TERI 1, MATSON, PAMELA1, VITOUSEK, PETER1, 1
ABSTRACT- We measured soil properties (nitrogen and phosphorus availability, pH, carbon content), and microbial community composition and metabolic activity (phospholipid fatty acid analysis, genetic ITS fingerprints, potential nitrification, substrate utilization profile), at several natural and fertilized forest sites along an age sequence in the Hawaiian Islands. We asked whether fertilization with nitrogen (N) and phosphorus (P) affects microbial community composition and metabolic activity in the same way that a natural gradient in N and P availability does. The sites show a distinct patterns in soil properties with age, and have distinguishable microbial communities. Soils at the natural sites range in age from 300 to 4.1 million years old. Intermediate aged sites have maximal soil N and P content, and also have the highest microbial metabolic activity. Diversity and evenness of substrate utilization (BiOLOG assay) varied, with the highest diversity at the oldest site. Microbial community metabolic profiles from the youngest (300 year old), intermediate (20,000 year old), and oldest (4.1 million year old) sites differ significantly (principal components analysis). Long-term application of nitrogen and phosphorus fertilizer reduced the diversity of substrates used by the microbial communities. Nitrogen containing substrates were the most affected. Nitrification potential increased from youngest to oldest sites, and in nitrogen fertilized sites. Changes in N availability (both natural and fertilizer) appear to be related to changes in microbial community parameters, whereas changes in P availability had less impact.
KEY WORDS: microbial community, fatty acid analysis, tropical soil