Anderson, C.R.; Rosen, M.R. 2001 Microbial ecology and geochemistry of soils containing iron pans . Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 2001/17 48 p.
Abstract: Soils in New Zealand, and elsewhere, often contain substantial zones of ferro-manganese concretions and pans (laterally continuous layers) that can affect soil quality and management. Soils containing concretions and pans from Southland, New Zealand, were investigated to determine links between microbial ecology and geochemistry. Three soil profiles were sampled at 10 cm intervals and assayed for 9 different populations of bacteria using selective media. Geochemical analysis was performed on the soils from the same intervals, and on groundwater from nearby wells. The largest concentrations of iron (Fe) and manganese (Mn) coincide with concretions. Nitrogen (N) and Carbon (C)are not correlated with Fe and Mn but may be depleted due to bacterial metabolism. Fe and Mn concentrations in groundwater are low suggesting that the source of these elements in the concretions and pans is . Lower Hutt: Institute of Geological & Nuclear Sciences. in situ weathering rather than groundwater. Numbers of iron oxidising organisms increase where concretions and pans are encountered, but manganese oxidising organisms decrease. Heterotrophic; sulphur-oxidising; and anaerobic populations have relatively consistent numbers at all depths within the profiles. Fifty organisms were selected for phylogenetic characterisation, of which only . Lower Hutt: Institute of Geological & Nuclear Sciences. Pseudomonas sp. is known to have significant interactions with Fe and Mn. These results suggest a possible link between concretion development and iron-oxidising microbial populations. (auth)