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Effects of agaricus lilaceps fairy rings on soil aggregation and microbial community structure in relation to growth stimulation of western wheatgrass (pascopyrum smithii) in Eastern Montana rangeland

The Can Caesar-TonThat, Erin Espeland, Anthony J. Caesar, Upendra M. Sainju, Robert T. Lartey, John F. Gaskin
Microbial ecology 2013 v.66 no.1 pp. 120-131
Agaricus, Bacillus (bacteria), Pascopyrum smithii, Pseudomonas fluorescens, Stenotrophomonas maltophilia, aggregate stability, bacterial communities, beta-N-acetylhexosaminidase, cellulases, community structure, enzyme activity, fruiting bodies, rangeland soils, rangelands, roots, soil aggregates, soil bacteria, soil depth, soil formation, soil fungi, soil quality, Montana
Stimulation of plant productivity caused by Agaricus fairy rings has been reported, but little is known about soil aggregation and the microbial community structure of the stimulated zone, particularly the communities that can bind to soil particles. We studied three concentric zones of Agaricus lilaceps fairy rings in Eastern Montana that stimulate western wheatgrass (Pascopyrum smithii): outside the ring (OUT), inside the ring (IN), and adjacent to the fungal fruiting bodies (SZ) to determine 1) soil aggregate formation and stability, 2) the microbial community composition and the N-acetyl-ß-D-glucosaminidase activity associated with bulk soil at 0-15 cm soil depth, and 3) the predominant culturable bacterial communities that can bind to soil adhering to wheatgrass root. In bulk soil, macroaggregates (4.75-2.00 and 2.00-0.25 mm) and aggregate stability increased in SZ compared to IN and OUT. The ratio fungal to bacteria (FAME) and N-acetyl-ß-D-glucosaminidase activity were the highest in SZ, suggesting high fungal population and high fungal cellulolytic activity. A soil sedimentation assay performed on the predominant isolates from root-adhering soil indicated more soil-binding bacteria in SZ than IN and OUT; Pseudomonas fluorescent and Stenotrophomonas maltophilia were the most efficient in binding soil in SZ, whereas Bacillus spp. were more efficient in IN. This study suggests that growth stimulation of western wheatgrass in A. lilaceps fairy rings may be attributed to the activity of the fungus by enhancing soil quality of bulk soil at 0-15 cm depth and influencing the amount and functionality of specific predominant microbial communities in the wheatgrass root-adhering soil.