Pyrosequencing Reveals Distinct Root-Zone Microbial Communities in Rangeland Restoration Plots.

In the Intermountain West (USA), cheatgrass (Bromus tectorum) has infested over 40 million ha of native sagebrush – bunchgrass communities and these communities are quite resistant to re-establishment of desirable native perennials. We examined microbial and nutrient dynamics in soils collected from replicated restoration plots established 27 years ago. We assessed ammonia–oxidizing bacteria (AOB) and archaea (AOA), soil bacteria, soil fungi and arbuscular mycorrhizal fungi (AMF) in response to contrasting soil history and plant species dominance. The AO community was examined by real-time PCR and clone libraries of amoA. The ratio of AOA /AOB amoA copies was higher (17) in the undisturbed native soil than in either the fumigated cheatgrass dominated (2.1) or the fumigated climax plant community soil (1.0). Bacterial and fungal community structure was assessed by amplified ribosomal spacer analysis (ARISA) and by tagged pyrosequencing. ARISA results suggested only minor shifts in the overall microbial community structure with the contrasting plant communities. Analysis of pyrosequencing data (deep amplicon sequencing) was more informative of community shifts lasting over 25 years.