DISSERTATION RESEARCH: The role of plant-soil interactions in woody shrub expansion in the White Mountains of California

由于环境和土地利用的变化，植物和动物的分布正在迅速变化。由于物种以不同的方式响应这些变化，生态群落的组成也在变化。一个重要的结果是木本灌木和树木向世界各地草原的移动或“侵占”。由于木本植物与非木本植物具有非常不同的特征，它们的入侵会产生巨大的影响。例如，入侵的植物可能会影响土壤中的微生物，如细菌和真菌。这些土壤生物对养分循环和土壤健康非常重要，因为它们分解腐烂的动植物物质，并以影响植物生长的方式为土壤施肥。因此，微生物种类的变化，或它们如何发挥作用，可能反过来影响该地区的其他植物。本研究研究了在加州怀特山脉上坡的一种木本植物，即山艾灌木，如何影响土壤微生物群落的组成和功能以及与之相关的植物物种。本研究将有助于改善木本植物入侵地区的土地管理策略。它将能够培训研究生和本科生，并与博物馆和当地保护团体建立联系。该项目将建立在先前的工作基础上，证明在过去的50年里，在怀特山脉，山艾树已经将其范围扩大到高山草原。该项目将整合田间和温室实验、用于表征土壤群落的现代分子和酶工具以及植物人口统计学模型，以：1)评估山艾树对土壤真菌群落结构和胞外酶生产的影响，以及2)确定这些地下变化如何反馈影响其他原生高山植物的性能。主要假设是，本地扩大范围的物种可能以对现有植物群落适应性有关键反馈的方式影响土壤微生物群落，包括改变养分循环和病原体与共生菌的相对频率。这项研究将使我们更全面地了解高山灌木扩张对地上和地下的影响。研究结果将为未来环境和景观变化下高寒植物物种的长期状况以及土壤微生物群落与植物生长性能之间联系的潜在机制提供有价值的信息。

Plant and animal distributions are changing rapidly as a result of environmental and land use change. Because species respond to these changes in different ways, the composition of ecological communities is also changing. One important result is the movement or "encroachment" of woody species of shrubs and trees into grasslands around the world. Because woody plant species have very different characteristics than non-woody plants, their encroachment can have dramatic effects. For example, encroaching plants may affect microbial organisms living in the soil, such as bacteria and fungi. These soil organisms are very important for nutrient cycling and soil health because they break down decaying plant and animal material and fertilize the soil in ways that affect plant growth. Therefore, changes in the species of microbial organisms, or how they function, could in turn affect other plants in the area. This research studies how a woody species, a sagebrush shrub, that is moving uphill in the White Mountains of California, affects composition and function of soil microbial communities and the plant species they associate with. This work will be helpful in improving land management strategies in areas experiencing woody plant encroachment. It will enable training of graduate and undergraduate students and outreach to a museum and local conservation groups.This project will build upon previous work demonstrating that in the White Mountains, sagebrush has been expanding its range into alpine grasslands over the last 50 years. The project will integrate field and greenhouse experiments, modern molecular and enzymatic tools for characterizing soil communities, and plant demographic modeling to: 1) assess effects of sagebrush on soil fungal community structure and extracellular enzyme production, and 2) determine how these belowground changes feed back to affect the performance of other native alpine plants. The primary hypothesis is that native range-expanding species may affect soil microbial communities in ways that have critical feedbacks on the fitness of the existing plant community, including altering nutrient cycling and the relative frequency of pathogens vs. mutualists. This research will result in a more complete understanding of the above- and belowground impacts of alpine shrub expansion. Results will provide valuable information on the long-term status of alpine plant species under future environmental and landscape change, and the underlying mechanisms that link soil microbial communities and plant performance.