Plant diversity and ecosystem services in wetlands

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Plant diversity and ecosystem services in wetlands There is accumulating evidence that the loss of biodiversity results in a reduction of the efficiency with which communities capture resources, produce biomass, recycle nutrients or resist invasion. This relationship between diversity and ecosystem functions and services may vary depending on soil fertility. For example, diversity effects may be more important in nutrient limited environments, such as natural grasslands, where the competition for resources is symmetric. In contrast, natural wetlands are among the most productive ecosystems on earth in part because they receive sediments and nutrients from the drained watershed. Yet, the ecological literature reports little empirical evidence from diversity experiments conducted in wetlands. As a result, little is known about the "diversity - ecosystem functions" relationship in this highly productive ecosystem. My research program focuses on the mechanisms by which biodiversity drives ecological processes and supports ecosystem functions and services in wetlands. For the current proposal, my students and I will 1) evaluate the effect of species richness and functional diversity on biotic resistance to invasion by exotic plant species in wetlands and 2) test whether ecological services in wetlands, as measured by water purification, increase with plant diversity due to complementarity effects. For the first objective, we will conduct a community restoration mesocosm experiment at the Institut de recherche en biologie végétale research site. We will manipulate initial species composition by applying seed mixtures of varying richness and functional diversity. We will then survey community reassembly and invasive plant species establishment over three years. This will allow us to establish the contribution of species and functional group identity, species and functional group interactions and abiotic conditions, and how these factors interact to determine biotic resistance. For the second objective, we will evaluate the effect of plant diversity and composition on nutrient assimilation and mineralization in wetland mesocosms with varying numbers of floating plant species. We will also compare measures of ecological processes in wetland soils with varying plant richness and functional diversity, both in experimental mesocosms and in a large wetland in southern Quebec. Because the processes for removing pollutants differ, our wetland experiments will offer an ideal situation for testing hypotheses on the multifunctionality of biodiversified ecosystems, i.e. how plant diversity may simultaneously affect several ecological functions. The results of our research program will not only allow us to understand, at the fundamental level, how plant interactions and diversity influence wetland ecosystem processes, but will also have implications for vegetation management, wetland restoration and design of constructed wetlands used for wastewater treatment.