Disturbances occur in all ecosystems, but there is no general theoretical framework that encompasses the various aspects of disturbance and their individual and interacting effects on biological communities. The frequency, intensity, duration, extent, and timing of disturbance can each influence the ability of species to coexist and the ability of new species to invade existing communities. Interactions among these aspects of disturbance further complicate their impacts, creating a need for a robust theoretical framework that can be applied to many ecosystems and to individuals, populations, and communities. An ecological niche-based theory of disturbance will be developed using analytical and simulation models, linking species traits to disturbance regimes and population dynamics. If successful, the project will create a common framework for a diverse literature on disturbance, significantly advancing our understanding of disturbance as a driver of biological diversity. The utility of the resulting models will be tested by applying them to three case studies: invasion and management of non-native thistles, fire and grazing disturbance interactions in Australia, and coexistence of species in deep-sea hydrothermal vent systems. Broader impacts of this project are present because human activities are changing disturbance regimes in virtually all ecosystems, with unknown consequences for species coexistence and diversity, and because disturbance has played a key role in the spread of many invasive species. A comprehensive theory of disturbance will inform scientists and natural resource managers when and where changes in disturbance are likely to pose threats to diversity or change the susceptibility of an ecosystem to invasive species.
Disturbances, which include perturbations such as fires, floods, hurricanes, climate change and volcanic eruptions, as well as agricultural practices, conservation management actions, and pest invasions, affect most, if not all, ecological systems. We developed a theoretical framework that unifies different types of disturbance, and allows their effects to be studied in terms of their common features. Specifically, we have explored the actions and interactions of the frequency, intensity, duration, extent, timing and autocorrelation of disturbance events as they affect species coexistence and invasions. We have also explored the underlying mathematical mechanisms of coexistence in variable environments. Our work helps to reconcile a large body of conflicting evidence about the role disturbance plays in determining biological diversity in communities; ignoring disturbance aspects (such as timing of disturbance) can lead to misinterpretation of empirical outcomes, and the possibility that management efforts are wasted, or even counter-productive. Using a combination of this conceptual framework, analytic and simulation modeling, and empirical work, we have contributed to case studies in diverse fields, including deep-sea biology, microbial ecology, weed science, land management, and conservation ecology, as well as to advances in fundamental ecological theory. Additionally, our results lay the groundwork for more efficient and cost-effective management practices. This work also supported the successful training and research of a postdoctoral fellow, a graduate student, and many undergraduate researchers in theoretical and empirical ecological approaches.
