Buckley, D. H. 2000. The diversity and dynamics of microbial groups in soils from agroecosystems. Ph.D. Dissertation, Michigan State University, East Lansing, Michigan, USA.

Citable PDF link: https://lter.kbs.msu.edu/pub/2704

Soil microbial communities are integrally involved in biogeochemical cycles, and their activities are crucial to the productivity and health of terrestrial ecosystems. Despite their relative importance, little is known about how microorganisms are distributed in the soil or the manner in which these organisms respond to environmental changes. To investigate the structure of microbial communities in soil, molecular techniques were used to determine the distribution and abundance of select microbial groups in soil. The influence of environment on microbial abundance was observed over a period of two years in a series of replicated plots that included agriculturally managed fields, fields abandoned from agriculture, and fields with no history of agriculture. Microbial community structure was characterized by using molecular phylogenetic techniques to monitor the relative abundance of eight of the most numerically abundant microbial groups in soil (the Alpha and Beta Proteobacteria, Actinobacteria, Cytophagales, Planctomycetes, Verrucomicrobia, Acidobacteria and the Eukarya).

The data described in this dissertation reveal that soil microbial communities are dynamic, capable of changing significantly at temporal scales relevant to seasonal events. In this background of temporal change, however, the relative abundance of particular microbial groups remains constrained by localized environmental characteristics resulting in reproducible patterns of community structure. Microbial community structure was observed to be remarkably similar among fields that shared a long-term history of agricultural management despite the differences in plant community composition and land management practices that had been maintained on the plots in recent years. In contrast, the microbial communities in fields that had never been cultivated differed significantly from those in fields that shared a long-term history of cultivation. These data indicate that the long-term effects of agricultural management on the soil alter microbial community structure and that these changes continue to be evident in fields abandoned from cultivation for as long as a decade. This dissertation provides insight into the structure of soil microbial communities and reveals that while soil microbial communities are dynamic, alterations in the soil environment can influence them fundamentally.

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