Ecosystem response to perturbation at multiple spatial scales

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We use greenhouses as a model to study the structure of food webs and interactions of various guilds in response to changes in temperature and food web complexity into our model ecosystem. Commercial greenhouses represent newly created ecosystems every year as plants are introduced. Because they are contained ecosystems, we can manipulate both the abiotic and biotic components to determine the stability of the system. Specifically, we propose to build ecosystems of varying trophic complexity within a greenhouse environment, then challenge the ecosystem with climatic changes (temperature), changes in upper trophic guilds (introduction of predators, parasites, omnivores), and changes in primary producer guilds (introduction of plant community complexity) in order to measure the role of these factors on ecosystem stability and response to perturbation. We propose to use a combination of small scale laboratory experiments with large scale greenhouse experiments in order to measure the effect of perturbation at multiple scales. All experiments will be conducted at three scales: small leaf arenas for direct behavioural observations; small 0.5m2 cages for short-term population-level studies and greenhouse compartment studies for long-term food-web stability studies. Interactions within and between trophic levels will be measured using direct behavioural observations, leaf counts of insects for population monitoring, prey preference and mortality rate experiments as well as stable isotope ratios for determination of predator and omnivore diets.