Collaborative Research: Testing for Cascading Effects of Habitat Fragmentation

合作研究：对生境碎片的级联效应的测试，道格拉斯·T·达特茅斯学院食物网理论为生态系统管理提供了一个有用的框架，并很好地补充了更传统的人口层面的方法。然而，食物网概念，包括关键物种和自上而下的级联，对受保护关注的生态系统的适用性尚不清楚。这个项目将研究南加州沿海鼠尾草灌木丛生态系统中捕食者-猎物相互作用的变化，这是由于与城市发展相关的栖息地碎片化造成的。该项目侧重于圣地亚哥县沿海的四种景观处理，它们暴露于城市边缘和碎片化的程度不同：大型栖息地区块的内部(1000公顷)、大型区块的城市化边缘、大型生境碎片(50-100公顷)和小碎片(5-20公顷)。拟议的研究将通过继续对鸟类进行人口统计学研究来扩展先前的工作，但同时估计中食动物、蛇和猛禽的丰度和活动，以估计它们的影响，并研究这些影响如何随着栖息地的碎片化而变化。这项工作将确定鸟巢捕食率、幼鸟和成年鸟的存活率，以及小型哺乳动物的丰度和存活率是否会随着碎片大小和捕食者组成的不同而变化。此外，它还将调查蛇和猛禽的作用，并通过实验处理和通径分析的比较来确定它们相对于哺乳动物捕食者的影响。通过比较鸟类对小型哺乳动物的反应，这个项目将解决以下问题：是否所有的初级消费者都容易受到级联效应的影响，或者分类群之间的生物差异是否会使一个群体比另一个群体更容易受到自上而下的监管。总体而言，该项目将培养18-25名本科生、3名研究生和1名博士后，并将为参加NSF环境生物学本科生指导教学计划的未被充分代表的学生创造研究机会。此外，这项研究将直接有益于当地野生动物机构和非营利性土地管理组织正在进行的管理和保护区设计目标。

Collaborative Research: Testing for Cascading effects of Habitat FragmentationBolger, Douglas T.Dartmouth CollegeFood web theory provides a useful framework for management of ecosystems, and compliments well the more traditional population-level approach. However, the applicability of food web concepts, including keystone species and top-down cascades, to ecosystems of conservation concern is unclear. This project will study changes in predator-prey interactions in the coastal sage scrub ecosystem of southern California cause by habitat fragmentation, associated with urban development. This project focuses on four landscape treatments in coastal San Diego County that vary in the degree of exposure to urban edge and fragmentation: interior of large habitat blocks (1000ha), urbanized edge of large blocks, large habitat fragments (50-100 ha) and small fragments (5-20 ha). The proposed research will expand previous work by continuing demographic studies on birds, but with simultaneously estimation of mesocarnivore, snake, and raptor abundance and activity to estimate their impacts and examine how these vary with habitat fragmentation. The work will determine if nest predation, juvenile and adult bird survival, as well as small mammal abundance and survival vary with fragment size and predator composition. In addition, it will investigate the role of snakes, and raptors and determine their impact relative to mammalian predators by comparisons across experimental treatments and by path analysis. By comparing bird responses to small mammals this project will address the question of whether all primary consumers are vulnerable to cascades, or if the biological differences between taxa make one group more susceptible to top-down regulation than another. Overall, this project will train 18-25 undergraduates, 3 graduate students and a post-doctoral student, and will creating research opportunities for underrepresented students participating in an NSF Undergraduate Mentoring in Environmental Biology teaching program. In addition, this research will directly benefit ongoing management and reserve design objectives of local wildlife agencies and nonprofit, land management organizations.