Rhizoplane and rhizosphere bacterial populations have different views of an upland grassland world.

Abstract : Soil microbial communities play an important role in nutrient cycling and nutrient availability, especially in unimproved soils. In grazed pastures, sheep urine causes local changes in nutrient concentration which is thought to be a source of heterogeneity in microbial community structure. However, microbial community structure is influenced by a variety of different factors operating at a range of spatial scales, the relative importance of which may depend upon the local environment in which the microbial communities exist. In this study, the relationship between bacterial and fungal rhizoplane and rhizosphere populations was investigated in an upland grassland using tRFLP. The extent to which the short term response of bacterial populations to external perturbation such as the application of synthetic urine was modulated by differences in their immediate environment was also investigated. Procrustean analysis of bacterial and fungal principal coordinate scores showed that the rhizoplane populations were significantly correlated. The analysis also suggested that the closeness of the relationship between the populations depended on the local environment. No significant relationship was found for rhizophere populations however. The effect of synthetic urine deposition on rhizoplane and rhizosphere populations was similar, though much more pronounced for rhizosphere populations, with an increasing divergence between urine treated and control populations during the first 15 days after treatment. In both cases this was followed by a return towards the initial state. Redundancy analysis suggested that of the environmental variables measured (DOC, pH, NH4 and NO3) only pH had a significant effect. These data indicate that in heterogeneous environments such as soil fine scale interactions must be taken into consideration if a complete understanding of soil microbial populations is to be obtained.
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Submitted on : Tuesday, September 25, 2007 - 6:48:55 PM
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Naoise Nunan, B.K. Singh, Peter Millard. Rhizoplane and rhizosphere bacterial populations have different views of an upland grassland world.. 9th Symposium on Bacterial Genetics and Ecology, Jun 2007, Wernigerode, Germany. pp.92. ⟨bioemco-00174956⟩



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