Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Peterson, Daniel G.

Committee Member

Magbanua, Zenaida

Committee Member

McNeal, Karen S.

Committee Member

Kingery, William L.

Committee Member

Matta, Frank B.

Date of Degree

5-11-2013

Document Type

Dissertation - Open Access

Major

Agronomy

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Organism succession during ecosystem development has been well studied for aboveground plant communities while the associated pattern of change in microbial communities remains largely unknown. A study was conducted along developmental sand-dune chronosequences bordering Lake Michigan at Wilderness State Park and Altamaha river valley of southeast Georgia with the hypothesis that soil bacterial communities will follow a pattern of change that is associated with soil, plant, and ecosystem development. This study site included 5 replicate sites along 14 dunes ranging in age from 105 to 500,000 years since deposition. The microbial composition and diversity in the soil was studied using bacterial tag-encoded FLX amplicon pyrosequencing of the 16S rRNA gene. As hypothesized, Bray-Curtis ordination indicated that bacterial community assembly changed along the developmental gradient at both sites. However, there was no seasonal effect at Michigan sites despite likely differences in plant carbon inputs. At the Michigan site, soil Ca, Mg levels and pH showed a significant log-linear correlation with soil development (r = 0.83, 0.84 and 0.81, respectively). Bacterial diversity represented by Simpson’s reciprocal index (Simpson’s 1/D) showed a steady decline from the youngest to the oldest dunes with the largest decline (212 to 58) during the initial stages of soil development (105 to 450 years). The change in plant species abundance was higher in the youngest sites than the older sites. This change was significantly correlated with the change in microbial community distribution (p < 0.0001; r = 0.56). Similarly, at Georgia sites, soil development showed significant log-linear correlation with soil base cations (Ca and Mg) (r = 0.93and 0.95). However, diversity indices and PLFA failed to show any particular change in trend across the developing chronosequences. When the results from both sites were used to study bacterial spatial patterns, local geochemical features were found to be a dominant factor in driving bacterial community structure, while geographic distance as a single factor could contribute to some community variation at a scale (50 – 1700 km). The results suggest that soil nutrients and plant community could be a strong driving force in shaping microbial community assembly across a developing soil ecosystem.

URI

https://hdl.handle.net/11668/18119

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