Factors affecting the community invasibility of tropical dry forests and the implications for ecological restoration.

摘要

Biological invasions pose a serious threat to the provision of ecosystem goods and services, the conservation of rare species, and the natural capital of human economies. Understanding the factors that make communities more or less invasible is a particularly prominent and contentious areas of ecological research today. In an age of rapid environmental change and constrained governmental budgets, the task of preserving natural areas, biodiversity, and ecosystem services as public resources is increasingly challenging. Yet, ecological restoration may provide the most efficient and cost-effective way to mitigate these challenges. While many comprehensive ecological restoration projects focus on exotic species control of particularly aggressive species, few restoration projects are informed by the results of invasibility research.;I utilized both observational and experimental approaches to study invasibility in tropical hardwood hammocks, a globally-imperiled tropical dry forest habitat that is also an excellent candidate community for restoration along its former range, including in metropolitan areas of South Florida. In Chapter 1, I surveyed the vascular flora of 13 tropical hardwood hammocks along the Miami Rock Ridge to determine which variables best predicted observed patterns of exotic species richness at different spatial scales. In Chapter 2, using constructed mesocosms with tropical hardwood hammock woody seedlings, I measured the effects of species richness and plant density on community productivity. In Chapter 3, I tested the effects of native species richness, native plant density, and invader propagule pressure on tropical hardwood hammock seedling layer invasibility, and also explored whether there was a link between community productivity and invasibility. In Chapter 4, I introduce a new model of restoration designed to enhance local biodiversity levels within metropolitan areas while also improving prospects for regional biodiversity conservation, and apply this model to a tropical hardwood hammock restoration. In Chapter 5, I assessed the relative contributions of native outplantings and habitat management to changes in community composition and structure over time in a tropical hardwood hammock restoration. Finally, in Chapter 6, I gauged the effects of varying native species richness and density treatments of outplanted populations of tropical hardwood hammock species on exotic recruitment at this restoration site.