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Biological insect pest control by natural enemies is an important component of sustainable crop production. To capitalize on the potential benefits of biological control, however, we need a clear understanding of the factors underpinning the biological and ecological relationships between pests and their natural enemies in agricultural landscapes. In my doctoral research, I explored how local and landscape composition influence the abundance, behaviors, and traits of insect pests and natural enemies, as well as the complex ecological interactions between them. Chapter 1 shows how different insect pest species within the same cropping system have contrasting responses to landscape composition, with some species having positive relationships with the proportion of non-crop habitats, while other species show the opposite response. Such contrasting responses create the potential for counterbalancing effects for pest control, where strategies to reduce one species may increase the abundance of another. Chapter 2 demonstrates that the effectiveness of augmentative releases of predators to enhance pest control is affected by the composition of the surrounding landscape. I found that increasing enemy abundance through augmentation may have net positive effects on pest control, but only in complex landscapes where habitat heterogeneity can create favorable conditions for complementarity between augmented and resident enemies. Chapters 3 focuses on the critical role of predator body size as a predictor of pest suppression. We found that communities with even representation of small and large-bodied species have greater pest control than communities dominated by either small or large-bodied predators. By influencing the body size distribution of predator communities, landscape composition consequently mediates the magnitude of pest suppression. Chapter 4 shows that landscape composition not only affects the consumptive, but also non-consumptive effects of predators on prey. I demonstrated that pest populations from landscapes with higher predator abundance exhibited considerable reductions in plant feeding in response to the presence of predators alone. Importantly, such landscape-driven changes in predator abundance may lead to reduced plant feeding damage, even in the absence of actual predation. Overall, my research shows that agroecosystem management that aims to harness the benefits of biological control should consider a landscape perspective because processes governing pest suppression by natural enemies operate at scales greater than individual fields.

Abstract: Oil sands mining in Alberta will destroy tens of thousands of hectares of boreal habitat. This land will need to be reclaimed. Current closure plans call for the construction of shallow open water wetlands to cover about 10-30% of the reclaimed landscape. Already, several trial wetlands have been constructed by mine operators, but no large-scale wetland creation has been attempted. For wetland reclamation to be successful, clear targets and tools for wetland monitoring and assessment are needed. I characterized the local- and landscape-level environmental conditions and aquatic plant communities in naturally occurring, undisturbed shallow open water wetlands to serve as a reference for comparison with reclaimed wetlands. I developed two related tools to evaluate wetland condition; one focusing on levels of abiotic stress, another on biological integrity. Using these tools, I conclude that current constructed wetlands differ from reference sites in terms of aquatic plant community structure, nutrient levels, and exposure to contaminants like naphthenic acids. Using multivariate analyses, I identified seven distinct biotic assemblages, two of which might serve as targets for future reclamation. I modelled the relationship between local- and landscape-level variables and aquatic plant diversity to test hypotheses about the relative importance of relationships between environmental variables and species richness. I conclude that diversity is more strongly related to local variables than surrounding land use, but that land use does play a role, albeit one that changes with the spatial scale considered. My results can inform reclamation practices by setting clear goals for future projects and by providing tools to measure progress towards them.