Collaborative Research: The structure of arthropod food webs: consequences of nutrient-loading scenarios for productivity, trophic composition and food-chain length.

尽管越来越多的景观经历了来自农业和发展的养分径流，但不同的养分输入制度对自然生境中食物网状结构的影响仍然知之甚少。这个项目的学术价值在于它扩展了食物网理论，将复杂的营养动态包括在内，这些动态不仅影响植物生产力，还影响消费者之间的互动。研究人员将使用操纵性田间实验和对不同氮素输入的沼泽的调查相结合的方法，研究营养补贴对以大米草为主的沿海盐沼中食物网动态的影响。这项研究的长期目标是了解一个以广泛的杂食性和行内捕食为特征的系统中初级生产力与食物链长度和营养成分之间的关系。这项研究的更广泛的影响超出了生态学理论的测试和发展。由于沿海湿地在防浪海岸线的生态和地质中发挥着关键作用，并且是商业鱼类和贝类的育苗场，因此它们的保护是主要关注的问题。城市发展和农业正在危及这些湿地；氮素径流增加了植物的生长，从而对所有其他盐沼居民产生了深远的影响。盐沼对反复添加氮素的恢复能力知之甚少。这项拟议的研究将为博士后研究员、研究生和本科生提供多样化的教育机会。调查人员计划参加哥伦比亚特区暑期青年就业计划，每年夏天从华盛顿特区招聘两名高中生。这项计划为哥伦比亚特区的居民和雇主牵线搭桥，这样学生就可以接触到新的职业机会。

The effects of contrasting nutrient-input regimes on food-web structure in natural habitats remain poorly understood, despite the increasing fraction of landscapes experiencing nutrient runoff from agriculture and development. The intellectual merit of this project lies in its expansion of food-web theory to include complex nutrient dynamics that affect not only plant productivity but also interactions among consumers. The investigators will examine the effects of nutrient subsidies on food web dynamics in coastal salt marshes dominated by Spartina cordgrasses using a blend of manipulative field experiments and surveys of marshes that vary in nitrogen inputs. The long-term goal is to understand the relationship between primary productivity and food chain length and trophic composition in a system characterized by extensive omnivory and intra-guild predation.The broader impacts of this study extend beyond the testing and development ofecological theory. Because coastal wetlands play a critical role in the ecology and geology of wave-protected shorelines and are the nursery grounds for commercial fish and shellfish, their conservation is of major concern. Urban development and agriculture are jeopardizing these wetlands; nitrogen runoff increases plant growth, which subsequently has profound effects on all other salt marsh inhabitants. The resilience of salt marshes to repeated bouts of nitrogen addition is poorly understood. The proposed research will provide diverse educational opportunities for a postdoctoral researcher, graduate and undergraduate students. The investigators plan to participate in the District of Columbia Summer Youth Employment Program to hire two high school students from the metropolitan Washington, DC area each summer. This program matches residents of the District of Columbia with employers so that the students may gain exposure to new career opportunities.