Detecting the effects of biological invasion and subsequent control efforts on wetland ecological processes
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Meadow and emergent cattail wetland communities in eastern North America are being replaced by an invasive lineage of <i>Phragmites australis</i>. This invasion has consequences for wetland ecosystem functions; including macronutrient storage due to invasion-driven changes in net primary productivity, decomposition rates and altered environmental site conditions. Because <i>P. australis</i> invasion degrades wetland ecological integrity, extensive efforts to control <i>P. australis</i>, mainly through herbicide application, have been undertaken. While the effects of <i>P. australis</i> control efforts on recovering plant communities has been studied, the success of these efforts at restoring ecosystem functions to pre-invasion ranges is unknown. My objectives were to 1) quantify the effect of <i>P. australis</i> invasion on macronutrient storage in the annual vegetative standing stock compared to uninvaded meadow and cattail marshes, and 2) to evaluate the success of large-scale, herbicide-based <i>P. australis</i> control efforts at re-establishing rates of net primary productivity, decomposition and environmental conditions to levels comparable to those in uninvaded marsh. I conclude that the effect of invasion on macronutrient storage was dependent on the plant community being replaced. Significant increases in annual macronutrient vegetative standing stock were observed when <i>P. australis</i>-dominated marsh was compared to meadow marsh, but few differences were observed between <i>P. australis</i> and cattail marsh. My analysis also revealed a reduction in carbon sequestration services one-year post-herbicide application. Emergent plant community recovery will likely be critical to increasing carbon sequestration in herbicide-treated marsh. My work indicates that <i>P. australis</i> invasion and subsequent control efforts represent trade-offs in ecosystem services. <i>Phragmites australis</i> invasion can increase macronutrient storage in the marsh but decrease biodiversity, and <i>P. australis</i> control efforts aiming to increasing biodiversity reduce carbon sequestration, at least temporarily. Understanding these net effects of <i>P. australis</i> invasion and control efforts on wetland functions informs decision makers considering whether to attempt <i>P. australis</i> eradication.
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Sarah Yuckin (2018). Detecting the effects of biological invasion and subsequent control efforts on wetland ecological processes. UWSpace. http://hdl.handle.net/10012/13888