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

食肉植物群落是一种罕见而多样的植物群落，只在美国东海岸以及加利福尼亚州北部和俄勒冈州南部的蛇纹状土壤生态系统中才能找到。这些群落的一个重要的生态方面是它们的边界，表现出高度的物种丰富度、多样性、初级生产力和沼泽空间特征的高度变异性。这些群落的大小和形状每年都会发生巨大变化，以应对一系列环境因素，特别是火和养分的可获得性。然而，人们对这些动态和复杂的边界交错带的具体性质知之甚少。这项博士论文研究项目试图确定俄勒冈州南部Darlingtonia fens中这些植被边界的性质，并从演替的角度解释它们的动态。该项目的重点将是检验这一假设，即随着时间的推移，在没有火的情况下，由于营养物质的增加，Darlingtonia fen群落变得更小，多样性变得更少。具体的研究目标是(1)确定群落边界上生物地球化学梯度的存在，(2)确定干扰和土壤性质对边界组成和结构的影响，以及(3)研究火灾对西部沼泽群落的历史和短期影响。三个不同焚烧历史的蛇纹草土壤生态系统将被用作试验点。进行这项研究的博士生将分析火灾和灭火对这些群落中发现的交错带的历史作用；描述交错带植被的群落组成和结构；分析土壤和水的物理和化学特征(如pH、N矿化、%P、%K、镁：钙比和重金属浓度)；以及分析蛇形土壤生态系统交错带对火灾的短期和长期群落响应，这是一种常见的干扰。该项目的成果具有理论和管理两方面的意义。该项目将评估西部达林顿沼泽的演替模式，并将为今后对这些生态系统和其他独特适应的生态系统的研究提供一个概念基础。需要确定沼泽交错带的作用、动态及其对多样性的影响，以确保目前和未来的有效管理。这项研究还将通过描述群落结构和生态系统动态，为美国林务局和自然保护协会制定管理战略提供生态学基础，因为它们与演替和干扰有关。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

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.