Effect of disturbance on ecosystem processes

One of the ecosystem management goals is to understand how disturbance regimes influence an ecosystem's traits and integrate the regimes into management criteria. This study contributes to the understanding of ecosystem energetics under disturbance by investigating the relationships between disturbance and ecosystem processes in the context of the current ecological paradigms: intermediate disturbance hypothesis (IDH), ecosystem maturity, and pulsing. The responses of gross primary productivity (GPP) and ecosystem respiration rate (ER) to water motion disturbance regimes were tested using open-top aquatic microcosms, and the mechanisms of the resultant patterns from the microcosms were suggested by computer simulation models.;Each microcosm developed a unique system and maintained a balance between GPP and ER through the self-organizing processes. Each microcosm showed a distinct relationship between disturbance regime and GPP. The mechanisms for the distinct relationships were explained by changes of efficiencies in energy flow pathways of a system under disturbances and by a disturbance threshold above which the efficiencies are permanently altered. The tests of the disturbance effects on GPP and ER under different maturities of microcosms supported the current theory on the ecosystem's development arguing that an ecosystem reinforces internal structures and thus becomes more resistant to disturbances over time. GPP and ER oscillated over time in the microcosms, and the wavelength and amplitude of the GPP and ER pulsing patterns were amplified by disturbance in microcosms' early stages of development, compared with those of an undisturbed system. As originally intended, the combined study of microcosms and simulation models provided new hypotheses on disturbance and ecosystem processes, which need to be tested further using microcosms, simulation models, or in the field.