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Title Centrifugal organization in a Georgia salt marsh plant community
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In this study I evaluate whether a centrifugal model helps explain vegetation patterns in a Georgia salt marsh using a combination of sampling data and manipulative experiments. The centrifugal model predicts that multiple stress gradients radiate out from a shared core habitat and that plants should occupy discrete ranges along these gradients. The results from this study indicated that there were two clear stress gradients, salinity and water-logging, along which species and habitats occupied discrete ranges, supporting the centrifugal model. The centrifugal model predicts that productivity should be greatest at the benign end of each stress gradient and least at the most stressful end. The results from this study generally supported the centrifugal model. Juncus and Borrichia, which occupied the most benign habitat, had the highest biomass. The stressful ends of the gradients, occupied by Salicornia virginica, short Spartina alterniflora and medium Spartina alterniflora, all had relatively low biomass. The centrifugal model predicts that diversity should be highest in intermediate levels of stress. Salicornia virginica and Spartina alterniflora zones always had the lowest species richness and diversity, supporting the centrifugal model. However, the Borrichia zone always had the greatest or second greatest level of species richness and diversity, not supporting the centrifugal model. The centrifugal model predicts that when species are transplanted outside of the benign habitat they will do poorly, with or without neighbors present, where species at the stressful ends of the gradients will do well when transplanted into the benign habitat without neighbors, but poorly when neighbors are present. The results of the transplant experiments strongly supported the centrifugal model. In conclusion, I found strong evidence that the centrifugal model was useful in explaining plant community structure in a Georgia salt marsh. This model also provides a unified theory for vegetation patterns in northeast and southeast USA salt marshes, where zonation due to high salinities caused by increased evapotranspiration in the low-latitude climates can be equated to the disturbance-caused temporary increases in salinity in high-latitude climates.

Contributor Alana R. Lynes

Lynes, A.R. 2008. Centrifugal organization in a Georgia salt marsh plant community. M.S. Thesis. University of Houston, Houston, Texas. 67 pages.

Key Words community ecology, Georgia, plants, salt marsh, Sapelo Island, SINERR Publication, Student Publication, UGAMI Publication
File Date 2008
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This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.