Changing the menu: Effect of omnivory on the structure of size spectrum in a plankton foodweb
| Autor: | Pei-Chi Ho, 何珮綺 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 Size spectra link the relationship between population density and organism body size. Empirical research revealed the connections of size spectrum with community structures and environmental conditions: a shallower spectrum and larger predator-prey size ratio corresponds to higher biomass transfer efficiency, and nutrient-rich systems. In this research, I use a nutrient-phytoplankton-zooplankton model to study the effects of omnivory and nutrient supply on the dynamics of the plankton system and structure of size spectrum. The increase of omnivory strength and new nutrient flux both destabilize the system, and the fluctuation amplitude of plankton populations increases with these two factors. Generally speaking, increase of omnivory strength and nutrient supply makes spectral slope constructed from long-term average plankton populations shallower, due to the increase of top predator. However, the range of slopes is smaller than observed in empirical research. When we take snapshots of size spectra in fluctuating systems, a wide range of slope values is observed and the range of slopes is similar to field observation if the system fluctuates regularly. The fluctuation of population offers an explanation to shallower spectral slopes in a plankton system. We also study the relationship between spectral slope and three frequently measured environmental factors: nutrient concentration, phytoplankton biomass and gross primary production. The result exhibits that nutrient concentration does increase with spectral slope, but the value of slope under similar nutrient condition is substantial. Long-term and frequent sampling is suggested if we want to observe the positive correlation between spectral slope and nutrient concentration. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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