Doctoral Dissertation Research: The Role of Community Boundaries, Environmental Gradients, and Disturbance in a Serpentine Soil Ecosystem: The Darlingtonia Fens of Southern Oregon

Portland State University, Portland OR

Investigators

Abstract

Carnivorous plant fens are rare and diverse plant communities found only on the eastern seaboard of the United States and in the serpentine soil ecosystems of northern California and southern Oregon. An important ecological aspect of these communities is their boundaries, which exhibit high species abundance, diversity, primary productivity, and high variability in the spatial characteristics of the fens. Size and shape of these communities can change dramatically from one year to the next in response to an array of environmental factors, especially fire and nutrient availability. The specific qualities of these dynamic and complex boundary ecotones are poorly understood, however. This doctoral dissertation research project seeks to determine the nature of these vegetation boundaries in the Darlingtonia fens of southern Oregon and to explain their dynamics in terms of succession. The focus of the project will be on testing the hypothesis that, over time and in the absence of fire, the Darlingtonia fen communities become smaller and less diverse due to an increase in availability of nutrients. Specific research objectives are (1) to determine the presence of biogeochemical gradients across the boundaries of the communities, (2) to identify the effects of disturbance and soil properties on boundary composition and structure, and (3) to examine the historical and short-term effects of fire on western fen communities. Three Darlingtonia serpentine soil ecosystems with different burn histories will be used as test sites. The doctoral candidate conducting this study will analyze the historical role of fire and fire suppression on the ecotones found in these communities; describe the community composition and structure of ecotone vegetation; analyze physical and chemical characteristics of the soil and water (such as pH, N mineralization, %P, %K, Mg:Ca ratio, and heavy metal concentration); and analyze short- and long-term community responses of a serpentine soil ecosystem ecotones to fire, which is a common disturbance. The outcomes of this project have both theoretical and management implications. This project will evaluate a successional model for western Darlingtonia fens and will provide a conceptual basis for future studies in these and other uniquely adapted ecosystems. The role of fen ecotones, their dynamics, and their impacts on diversity need to be identified to ensure effective present and future management. The research also will provide an ecological basis for developing management strategies by the U.S. Forest Service and The Nature Conservancy by describing community structure and ecosystem dynamics as they relate to succession and disturbance. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.