Invasive species are a serious concern for natural systems, mostly because they usually result in a decline of biodiversity. However, we know relatively little about how these invasive species affect other aspects of ecosystems. In particular, we lack knowledge about how plant invasive species may affect ecosystem services performed by the ecosystems they invade. Several plant species possess invasive strains that are more aggressive than their native counterparts. Yet relationships between native and invasive strains and their effects on ecosystem processes have not been thoroughly explored. This project addresses the effects of an aggressive invader, giant reed (Phragmites australis), on nutrient cycling, an important ecosystem process. The success in Phragmites spread has been attributed to changes in the patterns of land use, nutrient enrichment, and altered hydrological regimes. More recently, it has been speculated that its invasiveness could also be attributed to an invasive and more aggressive European strain. Although several studies on the effect of Phragmites australis on nutrient cycling have been conducted, they have mostly concentrated on brackish marshes and/or have not distinguished between native and exotic plant strains. Thus, the main goal of this study is to investigate the relationship between plant invasion and nutrient dynamics (with emphasis on the nitrogen cycle) by exploring if nutrient cycling differs among native plant communities and invasive and native strains of Phragmites australis in freshwater wetlands.
The potential for the proposed project to complement and broaden the participation of underrepresented minorities in science as well as to improve the quality of research and research training at Northeastern Illinois University (NEIU) is substantial. NEIU is a federally designated Hispanic-Serving institution (HSI) serving the Chicago metropolitan area, where ~27% of its students are Hispanic and many are first-generation college attendees. Through this project, NEIU will partner with researchers from the Chicago Botanic Gardens and Northwestern University, catalyzing a productive collaboration and broadening research impacts even further. In addition, the proposed project not only enhances research capabilities but will also positively affect curricular development and student preparation at several educational levels. The materials and instrumentation from the proposed project will be incorporated into: 1) the undergraduate biology curriculum to enhance the academic experience of students at NEIU and to better prepare them for graduate school, and 2) into the science curriculum at a neighboring high school of the Chicago Public Schools system (Northside College Prep High School).
Invasive species are a serious concern for several ecosystems, mostly because invasive species usually result in a decline of biodiversity. A myriad of studies have shown how diversity of native species declines when an invasive species invades a system. However, we know little about how these invasive species’ effects go beyond this negative effect on biodiversity affecting other aspects of ecosystems. In particular, we still lack knowledge about how invasive species affect ecosystem functioning or the ecosystem services they perform. This project addressed this gap in our knowledge by linking an important component of ecosystem functioning – nutrient cycling – to the invader plant, and extended beyond looking at changes in plant diversity once the invader comes into the system. In addition, this study incorporated how the genetic makeup of the invader affected ecosystem-level processes. Several invasive plants hybridize yielding genotypes that are more aggressive invaders than either parent. Yet correlations between different invasive genotypes and their effects on ecosystem processes have not been thoroughly explored. In this project, we explored the effects of an aggressive invader, Phragmites australis, on nutrient dynamics. The success in Phragmites’ spread has been attributed to changes in the patterns of land use, nutrient enrichment, and altered hydrological regimes. More recently, it has been speculated that its invasiveness could also be attributed to an invasive and more aggressive, exotic European genotype. Although several studies on the effect of Phragmites australis on nutrient pools, cycling, and other ecosystem processes have been conducted, they have been mostly done in brackish marshes and/or have not distinguished between native and exotic genotypes. Thus, the main goal of this study was to investigate the relationship between plant invasion and nutrient dynamics (with emphasis on the nitrogen cycle) by exploring if nutrient cycling functions (denitrification) and pools differ between exotic and native genotypes of Phragmites australis. We found that, contrary to our expectations, native Phragmites affected many environmental variables, including nutrients (ammonium, organic carbon, and phosphate; all increased as stem density increased) and nutrient cycling (elevated denitrification as stem density increased), whereas the exotic Phragmites strain did not. Results from this project contribute to gain a better understanding of the effects of these plant invaders with concomitant implications for restoration practices and conservation. If, as documented in this study, invasive exotic strains diminish ecosystem functioning relative to native strains, then restoration practitioners may need to pay special attention to the strain present in their fields. And this is an extremely difficult task as morphological traits between the native and invasive strains show substantial overlap. This issue is particularly relevant in wetland systems, the focus of this project, because wetlands are considered the "kidneys" of ecosystems such that they remove excess nitrogen pollutants through the process of denitrification. This research project provides evidence that wetland functions are indeed compromised by the invasion of wetlands by exotic plant species or strains. Because denitrification was found to be affected not only by the number of plant stems but also by the genetic identity of the plant species present, this study has increased our understanding of the factors that need to be taken into account when attempting to deal with invasive or problematic species. This project contributed to the development of human resources in science by providing opportunities for exposure to research and training to undergraduates and graduate students, by improving the research and technical skills of many of those participants, by exposing underrepresented groups to scientific research, and by providing exposure to scientific topics to K-12 students and teachers. In the combined 2 years of the project, the project involved a total of 10 undergraduate students (9 from Northeastern Illinois University; 3 Hispanic, first generation college attendees), 1 undergraduate who participated in Chicago Botanic Garden’s REU Program, 2 graduate students from Northeastern Illinois University, and 1 student from Chicago Botanic Garden/Northwestern University. The funding through this research starter grant: 1) provided students with an opportunity to conduct research in the environmental sciences area regarding problematic invasive species with a strong field component, 2) allowed students to develop a versatile skills tool-box of several commonly used techniques including molecular techniques, 3) enabled strong mentoring opportunities through faculty-student projects under a complementary approach involving the use of molecular tools to answer ecological-level questions, 4) created learning environments that encouraged student-faculty and student-student interactions, and 5) enriched interdisciplinary interactions among students and faculty across different institutions (e.g., NEIU, Chicago Botanic Gardens, Northwestern University, Chicago Public Schools system).
