Browsing by Author "Erickson, Richard A."
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Item Finite element simulation of space/time behavior in a two species ecological stoichiometric model(2016-08) Dissanayake, Chandani; Long, Kevin R.; Allen, Linda J. S.; Howle, Victoria E.; Peace, Angela; Erickson, Richard A.We simulate numerically a model of a plankton-algae ecosystem in which food quality (ecological stoichiometry) is included in addition to population and energy. An important feature of this model is that light absorption implies spatial variation in carrying capacity, so that we need to incorporate both space and time in our model ecosystem. Including mass transport by diffusion leads us to a reaction-diffusion problem. We have developed a finite element code for advection-reaction-diffusion ecosystems in 1,2, or 3 dimensions and carried out extensive validation studies. We then applied our software to the investigation of the dynamics of a model ecosystem with the stoichiometric model of LKE (Loladze2000), light absorption, and diffusive transport. Simulation results shows wave-like oscillatory behavior in a depth range 3.9056m and 16.4333m. The wave-like oscillatory behavior includes a region of high frequency oscillations in a depth range 14m-16m. We propose an explanation for this behavior through large phase shifts in nearby trajectories in phase space.Item Impacts of climate change on the population dynamics of Aedes albopictus and disease dynamics of dengue(2009) Erickson, Richard A.; Cox, Stephen B.; Allen, Linda J. S.; Long, Kevin R.; Presely, Steven M.Item Quantifying the impacts of toxicants on ecological populations(2013-08) Erickson, Richard A.; Anderson, Todd A.; Cox, Stephen B.; Long, Kevin R.; Salice, Christopher J.; Maul, Jonathan D.The closely related field of ecotoxicology and environmental toxicology have traditionally taken a reductionist approach and studied the effects of individual stressors on individual organisms. This approach fails to consider how multiple chemicals will affect populations and ecological systems. As an alternative, my doctoral research has focused on developing a population model and an interspecific competition model to better understand how pesticides and a simple mixture of pesticides affect natural systems. Using this system, I found that pesticides affect populations at levels not necessarily expected using traditional approaches. Specifically, malathion, pendimethalin, and permethrin were used as pesticides for the study system because they are found in the playa wetlands of the Southern High Plains. I also found that the mixture of pesticides was more toxic than the toxicity of individual pesticides, but the increase in toxicity was still difficult to quantify.