Abstract
The ability of rhizosphere diazotrophs to remain competitive during increased nitrogen availability in situ was tested in a salt marsh grass stand. Nitrogen (16.3 g m-2) or nitrogen (16.3 g m-2) and phosphorus (18.0 g m-2) were added to plots of short form Spartina alterniflora for either 2 weeks or 8 weeks. The diazotroph assemblage composition was monitored via the polymerase chain reaction using nifH specific primers followed by denaturing gradient gel electrophoresis (DGGE) analysis. DGGE profiles from the short-term experiments (2 and 8 weeks) were compared to profiles from control (no additions) and from long-term (>10 y) nutrient addition plots. Nitrogen fixation activity was assayed in each short-term treatment and control plot using an acetylene reduction technique. The control and nutrient addition DGGE profiles were very similar throughout the short-term experiments. One DGGE band that was prominent in the control plots was not found in the long-term nutrient addition plots. Diazotrophy may provide a competitive advantage for some species in this system, as indicated by results from the long-term nutrient amended plots. However, the rhizosphere environment in situ appears to limit the immediate impacts of increased nutrient availability on the diazotroph assemblage composition. Results from the short-term nutrient amended plots showed no measurable effect on the diazotroph assemblage. These results indicate substantial short-term stability of the diazotroph assemblage composition, but the potential for change in the face of long-term changes in nutrient availability.
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Received: 2 July 1999; Accepted: 13 August 1999; Online Publication: 6 March 2000
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Piceno, Y., Lovell, C. Stability in Natural Bacterial Communities: I. Nutrient Addition Effects on Rhizosphere Diazotroph Assemblage Composition. Microb Ecol 39, 32–40 (2000). https://doi.org/10.1007/s002489900192
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DOI: https://doi.org/10.1007/s002489900192