Impact of inundation and cattle grazing on the microbial community structure and function of floodplain soils. (4953)
Authors:
J.S. MacGregor* - Charles Sturt University
D.S. Baldwin - Murray Darling Freshwater Research Centre G.N. Rees - Murray Darling Freshwater Research Centre B.P. Wilson - Charles Sturt University
Abstract:
Floodplains are some of the most sought after land for agricultural use as their alluvial soil makes them highly productive areas. The Ovens River (Victoria, Australia) is one of the last remaining unregulated rivers in South East Australia and is floodplain is used heavily for cattle grazing. A mesocosom study determined if cattle grazing affected the soil’s response to inundation. Soil samples from grazed and ungrazed forested floodplain sites were flooded. Changes to microbial
community structure, microbial metabolic activity and carbon dynamics were determined. Inundation significantly changed the microbial community structure (16s rRNA diversity-T-RFLP analysis) and increased microbial respiration rates.
However other measurements of microbial activity, including enzymatic
degradation rates, did not increase significantly post flooding; but they tended to become more variable. Three dimensional fluorescence spectra showed shifts
occurred in carbon speciation, but 33.3mM KMnO4 oxidation measures showed the
‘labile’ carbon fraction did not change. Significantly different microbial
communities developed when grazed and ungrazed forest soils were inundated. No other effects of grazing were observed.
Speaker Information: Jessica MacGregor, Charles Sturt University, School of
Environmental and Information Sciences Charles Sturt University PO Box 789, Albury, NS 2640; Phone: +61 2 6051 9675; E-mail: [email protected]
Session Information: Monday, November 1, 2004, 12:25 PM-5:45 PM Presentation Start: 2:15 PM
Keywords: floodplain; bacteria; carbon; grazing