Environmental changes affect carbon assimilation to different degrees for wetland plants differing in nitrogen use strategies.
Waring, Elizabeth F.
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The use of commercially manufactured nitrogen in agriculture has increased the nitrate and ammonium levels of freshwater wetlands, which filter hydrological systems by absorbing nutrients from upstream. The resulting increase in available nitrogen has advantaged invasive plant species, which are washed into freshwater wetlands as seeds and plant parts. Invasive species can drastically alter a wetland’s composition and decrease its biodiversity by out- competing native species for nutrients. Carex stricta is an ecosystem engineer in sedge meadows across the United States’ Upper Midwest and is thus commonly used in wetland restoration efforts. Phalaris arundinacea is a common invader of the wetlands home to Carex stricta, including restored wetlands, though its strategy for invading wetlands is unknown. My purpose was to learn how the physiological processes used by P. arundinacea during invasions differ from those used by Carex stricta and other Carex species. Understanding these processes provided insight into P. arundinacea’s success as an invader and into how future invasions of P. arundinacea can be prevented. I completed the following objectives: (1) I identified the differences in carbon assimilation and leaf traits between Phalaris arundinacea and Carex stricta under various growth temperature and nitrogen availability conditions; (2) I examined the relationship between leaf traits in Phalaris arundinacea and Carex stricta and seasonal changes in nitrate and ammonium availability; and (3) I examined how nitrogen availability affects interspecies competition between Carex stricta and Phalaris arundinacea and between Carex lacustris and Phalaris arundinacea.