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United States Department of Agriculture

Agricultural Research Service

Title: Characterization of Microbial Communities in Agroecosystems

Authors
item Kennedy, Ann
item Gewin, Virginia

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 1, 1997
Publication Date: N/A

Interpretive Summary: Understanding soil microbiological responses to stress are essential to the current knowledge base for reasons of sustainability, reclamation, and environmental studies. The use of microbial functioning for examination of environmental stress and changes in biological diversity need to be exploited for the benefit of soil quality within agroecosystems. By looking at individual soil isolates and their differences with respect to the substrates they use at varying landscape positions, we can begin to determine the effects of stress on microbial functioning. Our data illustrate that using only diversity measurements in assessing management impacts is limited and the use of functional groups needs further analysis. The challenge ahead is to identify the level of microbial diversity, species composition, distribution, and the resiliency of the community to withstand stress and maintain a quality ecosystem. This research will benefit growers by expanding our knowledge of the impact of management on soil quality.

Technical Abstract: Substrate utilization and stress response patterns were assessed for bacteria, fungi, and actinomycetes in both wheat and prairie systems. Landscape position was also a potential source of variation among the samples. The data were further analyzed according to distinct isolate groupings. Bacterial isolates from the tilled systems had higher carbon source utilization as compared to prairie isolates, while actinomycetes isolates from the prairie system had higher carbon sources utilization as compared to the tilled system isolates. Overall, actinomycetes isolate responses were higher for both the tilled and prairie systems. Actinomycetes isolates also had the highest growth rates in the presence of stress for both systems as compared to bacterial and fungal isolates. Microbial substrate utilization differed with landscape position. The isolates from the tilled system had higher substrate utilization from foot slope, while the isolates from the prairie system had higher substrate utilization responses from side slope. Ridge top responses were similar. Relationship analyses among the substrates, isolates, and management systems support these findings. Actinomycetes had strong associations with arginine, sorbitol, xylan, streptomycin, and penicillin. Investigations of this nature can provide insight into the unknown of functional diversity. By isolating individual subsets of the community, and monitoring their nutritional strategies and performance under stress, we can gain valuable information into responses from different management systems.

Last Modified: 11/22/2014
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