DISSERTATION RESEARCH: The influence of invasive plants on nitrogen removal, via denitrification, in constructed wetlands

本论文的研究将比较澳大利亚多个人工湿地中有原生植被、入侵植被和无植被的样地的土壤微生物反硝化速率，以确定最佳的脱氮条件。人类活动造成了氮(N)污染，这种N正在影响全球的水体。过量的氮会污染饮用水，产生有毒藻类，并减少淡水生物多样性。此外，过量的氮会刺激藻类的水华；随后，这些藻类的死亡和分解可能会抢走水柱中的氧气。缓解这些问题的一种方法是通过建设湿地来加强生物脱氮。一般来说，湿地土壤是反硝化的热点，反硝化是微生物将溶解的硝酸盐(NO3-)转化为氮气的过程。因此，反硝化作用会从湿地和下游水生系统中去除氮。虽然湿地土壤通常是反硝化的理想土壤，但湿地植物群落结构如何影响反硝化速率，以及是否可以通过湿地植物群落的管理来优化反硝化速率，目前尚不清楚。人工湿地通常比自然湿地有更多的入侵物种，而且移除入侵物种是否会通过反硝化作用影响氮的去除也不清楚。植物群落结构可以影响湿地的野生动物价值和生物多样性，也可能影响其反硝化效果。拟议的研究将直接为人工湿地的规划和实施提供信息，并最终可用于帮助土地管理者创建和恢复更好地满足N缓解目标的湿地。

This dissertation research will compare soil microbial denitrification rates among plots with native vegetation, invasive vegetation, and plots without vegetation in multiple constructed wetlands in Australia in order to determine the optimal conditions for N removal. Human activities have resulted in nitrogen (N) pollution, and this N is affecting water bodies across the globe. Excess N can contaminate drinking water, produce toxic algae, and decrease freshwater biodiversity. In addition, excess N can stimulate algal blooms; subsequently, the death and decomposition of these algae can rob the water column of oxygen. One approach to mitigating these problems is to enhance the biological removal of N via the construction of wetlands. In general, wetland soils are hotspots for denitrification, which is the microbial conversion of dissolved nitrate (NO3-) to N gases. Denitrification, therefore, removes N from wetlands and downstream aquatic systems. Although wetland soils are generally ideal for denitrification, it is unknown how wetland plant community structure influences denitrification rates, and whether denitrification rates can be optimized via management of wetland plant communities. Constructed wetlands often have more invasive species than natural wetlands, and it is also unclear whether removing the invasive species influences N removal via denitrification. Plant community structure can influence a wetland's value for wildlife and biodiversity, and may influence its efficacy for denitrification, as well. The proposed research will directly inform the planning and implementation of constructed wetlands and ultimately can be used to help land managers to create and restore wetlands that better meet N mitigation goals.