Document: MAR-3-57-2

Changes in microbial community composition and carbon substrate utilization due to land use change in a tropical soil.

WALDROP, M.P.*, M.K.FIRESTONE and T.C.BALSER

University of California, Berkeley, CA 94720 1

Abstract:
If changes in the composition of the soil microbial community alter the physiological capacity of the plant community then such changes may have ecosystem consequences. We characterized microbial community parameters in soils from tropical forest (C3) and pineapple plantation soils (CAM) of different ages in Tahiti. We examined the relationships among community composition (PLFA), microbial biomass (CFDE), substrate utilization profiles (Biolog), lignocellulose degrading enzyme activities (MISSING CHARACTER ENTITY: beta-glucosidase, cellobiohydrolase, MISSING CHARACTER ENTITY: beta-xylosidase, phenol oxidase, peroxidase), and nutrient releasing enzyme activities (phosphatase, sulfatase). The natural isotopic gradient from C3 to CAM allowed us to analyze the d13C values of microbial phospholipid fatty acids and directly link groups of the microbial community (individual PLFAs) with the utilization of young plantation and older forest carbon. Conversion from forest to agriculture significantly (P<0.05) decreased nutrient availability in the soil, microbial biomass, MISSING CHARACTER ENTITY: beta-glucosidase and sulfatase activity, and produced compositionally and functionally distinct microbial communities. Although changes in a functional diversity index (Biolog) did not correlate with changes in community composition (PLFA), changes in the specific activity of the enzymes were significantly correlated with changes in community composition. We also determined that different groups within the microbial community use different carbon sources and that changes in community composition co-occurred with changes in the pools of carbon utilized. We can link microbial community composition to carbon utilization and degradation using 13C-PLFA and enzyme activities.

Keywords: Microbial community, natural abundance 13C-PLFA, Enzyme activities, Biolog

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This abstract is being presented at: 9:30 AM in session:
Oral Session #23: Soil Ecology.