Plant communities are structured by their soil interactions. These interactions can be both positive in the form of mutualisms and negative in the form of parasites and pathogens. Spatial structure is inherent to all terrestrial systems and therefore could play an important role in mediating these positive and negative feedbacks. For costly mutualism to be stable, a mechanism such as spatial population structure must exist to prevent non-mutualist individuals from invading. Limited dispersal can generate the spatial structure required to stabilize mutualism. Using a computer simulation, I found that despite the inherent advantages of increased dispersal distance, mutualists evolved short dispersal when competing with non-mutualists. Negative feedbacks can promote plant species coexistence, a central question in ecology. I extended a 2-species feedback model to include three or more species and analytically derived the invasion and stability criteria for the 3-species case. I identified qualitatively new community structures that result in species coexistence. I then used computer simulation to determine conditions for stability in communities with greater than 3 species and found that increased species richness decreased community stability in randomly assembled communities. Then using meta-analysis, I compared expectations based on randomly assembled communities to communities assembled from published data, and found that coexistence is more common and feedbacks are more negative in nature than expected by random chance. I also found a negative correlation between average feedback and relative species abundance, a result that contradicts recent empirical results. Therefore, I developed a spatially explicit computer simulation in order to see how spatial processes affect communities structured by negative feedbacks. I found that as the size of both the dispersal and interaction neighborhoods increased the slope of the relationship between feedback and abundance decreased. Finally, using a greenhouse experiment, I found that spatial structure in the rhizosphere can alter the direction and magnitude of species specific plant-soil feedbacks.
|Advisor:||Bever, James D.|
|Commitee:||Clay, Keith, Lively, Curt, Lloyd, Elisabeth, Watson, Maxine|
|School Location:||United States -- Indiana|
|Source:||DAI-B 74/02(E), Dissertation Abstracts International|
|Subjects:||Ecology, Soil sciences|
|Keywords:||Coexistence, Feedback, Mutualism, Mycorrhizae, Plant communities, Spatial structure|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be