DISSERTATION RESEARCH: Synthesizing the Mass-ratio and Novel-trait Hypotheses to Explain Variability in the Impact of Plant Invasions on Coupled C and N Cycling

入侵植物物种可能对维持生态系统和人类健康的生态系统服务产生重大有害影响。然而，这些影响的变数很大，很难预测，这给决策者决定如何分配有限的资源来应对植物入侵带来了困难。该项目旨在了解影响美国东部分布最广的入侵植物之一--高粱(Microstegium Vimineum)对碳和氮循环影响的因素。具体地说，该项目将调查描述入侵者影响变化的两个假设的相对重要性：第一，物种在它们最丰富的地方影响更大；第二，物种在与栖息植被的功能最不同的地方对感兴趣的生态系统过程产生更大的影响。研究人员将使用观察性研究和实地操作相结合的方法来验证这些假说，并使用建模方法将入侵影响中的可变性驱动因素与生物地球化学过程联系起来，生物地球化学过程控制不同土壤环境中植物凋落物的营养通量。建模方法将探索入侵者的特征和丰度，以限制或促进其对碳和氮循环的影响。通过结合观察、实验和建模的方法，这项研究将提供一个独特而强大的综合，既为该物种的管理提供信息，又解决基本生态利益的关键问题。确定单个物种在控制生态系统过程中所起的作用是生态学的一个重大挑战？S：由于人类活动导致生物的全球分布发生变化。该项目探讨了单个入侵植物物种如何影响对全球气候、土壤肥力、生态系统生产力和生态系统复原力产生重大影响的关键生态系统过程。这项研究将产生新的信息，说明非本土物种入侵对生态系统功能的影响是如何通过共存物种的个体和相互作用影响来调节的。这些信息将完善关于不同条件下非本土物种入侵后果和机制的一般理论，并将提高我们预测生物入侵何时何地产生最大影响的能力。这项研究将在三个关键领域产生更广泛的影响。首先，该项目将为每个学年的本科生提供优秀的经验和广泛的培训，并将大大提高博士生S的研究水平。第二，督导人员会透过网站、网志、公众介绍和刊物，向土地管理人、其他生态学者和公众人士宣传他们的研究结果。第三，该项目将为预测入侵物种在哪里以及在什么条件下产生最大影响提供重要信息。具体地说，重点物种微囊藻是东部落叶林中最常见的入侵植物之一，在那里它对群落和生态系统有重大影响。提高土地管理人员有效瞄准入侵移除和恢复工作的能力，将极大地加强美国东部的保护和管理工作。

Invasive plant species can have significant detrimental effects on ecosystem services that sustain ecosystem and human health. These impacts, however, are highly variable and hard to predict, raising difficulties for policy makers deciding how to allocate finite resources to address plant invasions. This project aims to understand factors that drive variability in the impact of one of the most widespread invasive plant species in the eastern US, Microstegium vimineum (Japanese stiltgrass) on carbon and nitrogen cycling. Specifically, the project will investigate the relative importance of two hypotheses that describe variation in invader impacts: first, that species have greater impacts where they are most abundant; and second, that species have greater impacts where they function most differently from the resident vegetation with respect to the ecosystem process of interest. Investigators will use a combination of observational studies and field manipulations to test these hypotheses, and a modeling approach to link drivers of variability in invader impacts to biogeochemical processes that control nutrient fluxes from plant litter across varying soil environments. The modeling approach will explore invader characteristics and abundances that limit or promote its impact on carbon and nitrogen cycling. By combining observational, experimental and modeling approaches, this research will provide a unique and powerful synthesis that will both inform the management of this species and address key questions of basic ecological interest.Determining the role that individual species play in controlling ecosystem processes is one of ecology?s grand challenges as global distribution of organisms shift due to human activity. This project addresses how individual invasive plant species can impact critical ecosystem processes that have a strong influence on global climate, soil fertility, ecosystem productivity, and ecosystem resilience. This research will produce novel information on how the impacts of non-native species invasions on ecosystem functions are mediated by the individual and interactive effects of coexisting species. Such information will improve general theory on consequences and mechanisms of non-native species invasions under different conditions, and will advance our ability to predict when and where biological invasions will have the greatest effects. This research will result in broader impacts in three key areas. First, the project will provide excellent experience and broad training for an undergraduate student each academic year of the project and will substantially improve a PhD student?s research. Second, the PIs will disseminate their research findings to land managers, other ecologists, and the general public through a web site, web blog, public presentations, and publications. Third, the project will provide important information for predicting where and under what conditions invasive species will have the greatest impacts. Specifically, the focal species, Microstegium, is one of the most common invasive plants in eastern deciduous forests where it has significant community and ecosystem impacts. Improving the ability of land managers to efficiently target invasive removal and restoration efforts will greatly enhance conservation and management efforts in the eastern U.S.