Plant interactions and ecosystem function in wetlands

在过去二十年中，越来越多的证据表明，生物多样性的丧失导致社区获取资源、产生生物量和循环养分的效率降低。然而，在这一主题的文献中，关于草原和初级生产措施的研究无可争议地过于代表性，尽管湿地在全球生化循环中的重要性得到了认可，但我们对植物多样性与生态属性和功能之间的基本关系的理解仍然有限。在湿地的多样性和功能之间的关系中，一个可能使湿地与众不同的特性是一种单一的、通常是外来的维管植物物种在当地占主导地位。入侵植物对湿地多样性的负面影响是众所周知的，但是否伴随着生态系统过程和服务的减少尚不清楚。我的研究项目主要集中在高产植物物种之间的竞争相互作用以及入侵物种对生态系统功能和服务造成的多样性丧失的影响。对于目前的提案，我和我的学生将测试是否1)湿地的生态服务，通过营养循环和水净化来衡量，由于互补效应，随着植物多样性的增加，湿地的生态服务是否会增加；2)湿地中竞争性克隆物种的扩张是否会降低与生态服务相关的生态功能和属性。为了第一个目标，我们将评估植物多样性和组成对养分同化、矿化和微生物活动的影响，以处理湿地生态系统为模型，在不同的植物物种数量和不同的营养条件下。第一个实验将使用两种湿地大型植物——环凤尾Phalaris arundinacea和芦苇（Phragmites australis）的连接盆地，这两种湿地植物在根系结构和季节活动方面存在差异。在第二个实验中，我们将在自由水湿地生态系统中使用1至4种漂浮植物的组合。在这两个实验中，将监测水质参数、植物参数和微生物活性，以测试植物多样性和组合对湿地过程的影响。第二个目标，我们将监测魁北克南部大片湿地的生态属性和植物空间动态，在密集的、几乎单特异性的无性系物种（芦苇，芦苇，美洲，Phalaris arundinacea）斑块内外。为了补充实地调查，我们将采用原始的中生态实验来测量植物相互作用对生态属性的影响，该实验旨在再现湿地植物物种之间的无性系生长竞争。我们的研究结果将使我们在基础层面上了解植物相互作用和多样性如何影响湿地生态系统过程。此外，我们的研究结果将对植被管理、湿地恢复和用于废水处理的人工湿地具有指导意义。

Over the last two decades, there has been accumulating evidence that the loss of biodiversity results in a reduction of the efficiency with which communities capture resources, produce biomass and recycle nutrients. Yet, there is an undisputed over-representation of studies on grasslands and primary production measures in the literature on this subject, and despite the recognized importance of wetlands in global biochemical cycles, our understanding of the fundamental relation between plant diversity and ecological attributes and function is still limited for this system. One property that may set wetlands apart in their relation between diversity and functions is the common, local domination of a single – often exotic – vascular plant species. The negative impact of invasive macrophytes on wetland diversity is well known, but it is unclear whether it is accompanied by a decrease in ecosystem processes and services. My research program focuses on competitive interactions between highly productive plant species and the impact of the loss of diversity caused by invasive species on ecosystem functions and services. For the current proposal, my students and I will test whether 1) ecological services in wetlands, as measured by nutrient cycles and water purification, increase with plant diversity due to complementarity effects and whether 2) expansion of competitive clonal species in wetlands reduces ecological functions and attributes associated with ecological services. For the first objective, we will evaluate the effect of plant diversity and composition on nutrient assimilation, mineralization and microbial activity using treatment wetland mesocosms as model ecosystems, with varying numbers of plant species and under several different nutritional conditions. A first experiment will use connected basins of Phalaris arundinacea and Phragmites australis, two wetland macrophytes that differ in root system architecture and seasonal activity. In a second experiment, we will use combinations of 1 to 4 floating plant species in free water wetland mesocosms. In both experiments, water quality parameters, plant parameters and microbial activity will be monitored to test the effect of plant diversity and combination on wetland processes. For the second objective, we will monitor ecological attributes and plant spatial dynamics in a large wetland area of southern Quebec, within and outside of dense, nearly monospecific patches of clonal species (Phragmites australis var. australis, Phragmites australis var. americana, Phalaris arundinacea). To complement the field survey, we will measure the effect of plant interaction on ecological attributes using an original mesocosm experiment designed to reproduce competition between wetland plant species with clonal growth. Results of our study will allow us to understand, at the fundamental level, how plant interactions and diversity influence wetland ecosystem processes. Furthermore, our findings will have implications for vegetation management, wetland restoration and constructed wetlands used for wastewater treatment.