DISSERTATION RESEARCH: Effects of Soil Nitrogen Enrichment on the Chemical Mediation of Multi-Trophic Interactions

虽然大多数温带陆地生态系统的氮素仍然有限，但来自人类活动的氮素输入正在快速增加。本项目将研究氮肥对植物-食草动物和食草动物-捕食者相互作用的影响。土壤氮素的增加可能通过改变植物生产力、营养品质和防御化学物质来影响这种相互作用。这些对植物的直接影响，反过来可能会同时影响食草动物和捕食者。这个项目研究了一种受到化学防御的入侵植物(斑点蟾亚麻、亚麻黄、玄参科)、一种储存这些植物防御化合物的专业昆虫草食动物(亚麻落叶者、新月金龟子、夜蛾科)和几种无脊椎动物捕食者之间的相互作用。这些相互作用将在温室和田间试验中进行研究，在这些试验中，植物在不同的氮素添加水平下生长。这些结果将有助于理解土壤氮素增加影响这种相互作用的明确机制。该项目是首次对这种入侵植物的化学生态学进行研究，并引进了一种生物防治昆虫来管理这种物种。入侵植物对当地生物多样性构成了重要威胁，氮沉积可能会促进这些物种入侵栖息地的攻击性。这项研究的信息将为改进入侵植物的生物防治工作提供见解，这种入侵植物作为一种草原杂草具有生态和经济意义。此外，这项研究的更广泛影响包括促进研究人员和土地管理者之间的合作，以及教育公众关于环境变化和植物入侵的知识。

While most temperate terrestrial ecosystems remain nitrogen limited, nitrogen inputs from human activity are increasing at a rapid rate. This project will examine the influence of nitrogen enrichment on plant-herbivore and herbivore-predator interactions. Soil nitrogen enrichment may influence such interactions through changes in plant productivity, nutritional quality, and defensive chemistry. These direct effects on plants, in turn, may affect both herbivores and predators. This project examines interactions between an invasive plant that is chemically defended (Dalmatian Toadflax, Linaria dalmatica, Scrophulariaceae), a specialist insect herbivore that stores these plant defense compounds (Toadflax Defoliator, Calophasia lunula, Noctuidae), and several invertebrate predators. These interactions will be investigated in greenhouse and field experiments in which plants are grown under varying levels of nitrogen addition. The results will contribute to understanding the explicit mechanisms by which soil nitrogen enrichment may influence such interactions. This project represents the first study of the chemical ecology of this invasive plant and a biological control insect that has been introduced to manage this species. Invasive plants pose an important threat to native biodiversity and the aggressiveness of these species to invade a habitat may be facilitated by nitrogen deposition. Information from this research will provide insight for improving biocontrol efforts for an invasive plant that has ecological and economic significance as a rangeland weed. Further, the broader impacts of this research include fostering collaborations between researchers and land managers as well as educating the public about environmental change and plant invasions.