Graduate Program
Biological Sciences
Degree Name
Master of Science (MS)
Semester of Degree Completion
2005
Thesis Director
Scott Meiners
Thesis Committee Member
Eric Bollinger
Thesis Committee Member
Robert Fischer
Abstract
Plant communities change through time as species respond to changes in their biotic and abiotic environment. Biotic factors influencing plant communities can include species invasion, competition, or herbivory, whereas abiotic factors can include drought, fire, or nutrient deposition. Although factors influencing community structure have been extensively documented, the mechanisms by which communities respond to disturbances are not well understood. To address this problem, my thesis research considered two perturbations, exotic species invasion and drought, in each case I specifically relate species turnover to changes in community structure. The overall goal of this project was to evaluate the utility of using species turnover dynamics as a simple conceptual framework for assessing general mechanisms of community change. I determined species turnover at the community and population scales to identify 1) the mechanisms driving exotic species impacts and 2) the mechanisms of community change associated with drought.
Exotic species invasion resulted in declines in diversity caused by reduced colonization rates, and not increased extinction rates for all invaders. Populations differed in their susceptibility to invasion impacts, with most species showing reduced colonization rates. These results suggest that establishment limitation may be a general mechanism of invasion impacts. During a two-month drought, diversity and cover declined due to both reduced colonization and increased extinction rates. Diversity and cover quickly rebounded in this system during a colonization window opened by drought. Surprisingly, drought had little long-term effect on community structure and initiated only subtle changes in the understory community composition. Population dynamics appeared to be generally driven by stochastic species turnover within sites and not by large-scale shifts in species performance.
Within this system, community response to perturbation appears to be primarily driven by colonization dynamics. In both perturbation scenarios, exotic species invasion and drought, colonization rates changed and led to altered community composition. Although the mechanisms of community change were uniform across disturbance type, changes occurred at a local scale and not uniformly across the entire community. The study resulted in several interesting findings that improved our understanding of the mechanisms governing community response to disturbance and allowed us to make testable predictions on the response of communities to disturbance. This approach can be used in other systems to determine the generality of these mechanisms as drivers of community change across a suite of disturbance types.
Recommended Citation
Yurkonis, Kathryn Anne, "Plant species turnover as a mechanism of community change in response to biotic and abiotic perturbation" (2005). Masters Theses. 929.
https://thekeep.eiu.edu/theses/929
