Doctoral Dissertation Research: Dynamics in Montane Grasslands: The Invasion of an Exotic Species in Rocky Mountain National Park

国家公园管理局和其他以保护为导向的组织历来试图保持公园土地和荒野地区的自然条件，但外来物种的入侵往往改变了本土植物群落。固氮植物改变了生物地球化学过程，为未来的外来入侵提供了便利。本博士论文研究了落基山国家公园山地草原外来物种黄三叶的空间竞争效应和资源竞争效应。初步分析表明，药用植物入侵扩散到当地群落，并由于养分有效性降低和土壤小气候变化而导致物种组成发生变化。继续的研究将集中在这样的假设上，即本土物种将从规定的燃烧和氮素处理中受益，而药用植物的传播和密度将减少。本项目采用的研究方法包括对入侵斑块和非入侵斑块的重复干扰地的土壤和植被进行采样。初步结果表明，整个季节药用地鼠扩展超过了原来绘制的边界，不同斑块的物种组成是不同的。土壤分析表明，药用植物斑块的氮素有效性、净矿化作用和土壤水分较低。历史航拍照片、全球定位系统和地理信息系统将被用来绘制外来入侵地图。在该项目的后期阶段，现场方法将包括在几个地点进行规定的燃烧和沿补丁边缘进行氮气处理。这个项目将提供对生物入侵和化学变化过程的新见解。除了产生关于这些生物地理和生物地球化学过程的基本知识外，该项目还将为土地管理者提供实用信息，特别是与规定的火灾和氮素处理在保护自然植被群落中可能发挥的作用有关的信息。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。

The National Park Service and other conservation-oriented organizations historically have tried to maintain park land and wilderness areas in their natural conditions, but the invasion of exotic species often has altered indigenous plant communities. Nitrogen-fixing plants alter biogeochemical processes and facilitate future exotic invasions. This doctoral dissertation research project addresses spatial and resource competitive effects of an exotic species, yellow sweet clover (Melitotus officinalis), in montane grasslands in Rocky Mountain National Park. Preliminary analyses show that M. officinalis invasion spreads into native communities and induces an altered species composition from lowered nutrient availability and soil microclimate changes. Continued research will focus on the hypotheses that native species will benefit from prescribed burning and nitrogen manipulations while M. officinalis spread and density will decrease. Research methods to be used in this project include sampling soil and vegetation in replicate disturbed sites of invaded and non-invaded patches. Preliminary results show that M. officinalis expanded past original mapped boundaries throughout the season, and species composition is different between patches. Soil analysis shows lower nitrogen availability, net mineralization, and soil moisture in patches occupied by M. officinalis. Historical aerial photographs, global positioning systems, and geographic information systems will be used to map exotic invasion. Field methods during the latter stages of the project will incorporate prescribed burning in several sites and nitrogen manipulations along patch edges. This project will provide new insights into the processes of biological invasions and altered chemical processes. In addition to generating fundamental knowledge about these biogeographic and biogeochemical processes, this project will provide practical information for land managers, especially as it relates to the role that prescribed fires and nitrogen manipulations may play in the preservation of natural vegetation communities. 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.