Plant interactions and ecosystem function in wetlands

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Over the last two decades, there has been accumulating evidence that loss of biodiversity results in a reduction of the efficiency with which communities capture resources, produce biomass and recycle nutrients, but it remains unclear whether this overall pattern applies to highly productive, nutrient-rich wetlands. Competition among vascular plants can be intense in wetlands, often resulting in the local dominance of one or a few (sometimes exotic) species. My research program focuses on competitive interactions between highly productive plant species and the impact of 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 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 with varying numbers of plant species and under several different nutritional conditions. For the second objective, we will monitor ecological attributes and spatial dynamics within and outside dense, nearly monospecific stands of clonal species in a large wetland area of southern Quebec. 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 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 constructed wetlands used for wastewater treatment.