CAREER: Nitrogen exchange and removal in riparian wetlands - the role of vegetation

过量的生物有效氮严重恶化了美国中西部农业管理地区的溪流和河流的水质。该地区的大部分氮负荷发生在河流与河岸湿地的水文连接的高流量、洪水条件下。尽管有明确的证据表明湿地具有脱氮作用，但对脱氮效率的机理认识还很欠缺。利用野外实验、现场观测和遥感观测相结合的方法，该项目调查了湿地植被如何调节河岸湿地物理和生物上不同区域的水分运输和氮素去除速率之间的相互作用。要利用湿地的潜力来减缓地表水质量的退化，就需要这些知识。此外，管理水质的一个核心挑战是依赖自愿采取保护行动来减少氮投入。该项目的教育和宣传部分将提供机会，以吸引人的环境和形式与社区成员分享与水质管理有关的科学知识。总体而言，该项目响应了科学和社会需求，以推广我们对湿地系统性能的理解，并确定在不断扩大的地方、国家和全球农业足迹下解决水质受损问题的途径。该提案的总体目标是促进科学和学生对河岸湿地植被在高水流、洪涝条件下促进氮去除的作用的理解，在高水流和洪水条件下，当最活跃的氮负荷发生时。具体地说，本项目将在两个空间尺度上调查滨河湿地植被分布和结构对氮去除的影响。在河段尺度上，研究河段沿线的观测数据将量化湿地淹没的深度和程度、与河道的水力交换率、植被结构和河段的净氮去除。在植被冠层尺度上，将通过田间试验来测量氮素转化和去除速率随流量和冠层内植被结构的变化。将通过建模方法比较冠层和覆盖范围的净脱氮率，以确定局部尺度的相互作用是否能够解释净脱氮模式。该项目还寻求通过注重交流的体验式教育倡议和学生主导的外展活动促进水质管理，同时增加学生的多样性。教育活动的结构将首先通过在课程中的主动学习来培养大学生的专业知识，然后让学生通过当地的科学中心及其成功的现有外展计划传授他们所学到的知识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Excessive biologically available nitrogen has severely degraded water quality in streams and rivers of the agriculturally managed midwestern United States. Most nitrogen loading in this region occurs during high streamflow, flooded conditions when rivers are hydrologically connected to riparian wetlands. Despite clear evidence of wetland nitrogen removal, a mechanistic understanding of removal efficiency is lacking. Using a combination of field experiments, in situ and remote sensing observations, this project investigates how wetland vegetation regulates the interplay between water transport and nitrogen removal rates in physically and biologically distinct regions of riparian wetlands. This knowledge is required to harness the potential of wetlands to mitigate surface water quality degradation. In addition, a central challenge in managing water quality is the reliance on voluntary adoption of conservation actions to reduce nitrogen inputs. The education and outreach components of this project will provide opportunities to share science relevant to water quality stewardship with community members in an engaging setting and format. Overall, this project responds to a scientific and societal demand to generalize our understanding of wetlands system performance and identifies pathways to address impaired water quality under the expanding local, national and global footprint of agriculture.The overarching goal of this proposal is to advance scientific and student understanding of the role of riparian wetland vegetation in facilitating nitrogen removal during high streamflow, flooded conditions when most reactive nitrogen loading occurs. Specifically, this project will investigate the effect of riparian wetland vegetation distribution and structure on nitrogen removal at two spatial scales. At the reach scale, observational data along the study reach will quantify wetland inundation depth and extent, hydraulic exchange rate with the channel, vegetation structure and net nitrogen removal along the reach. At the vegetated canopy scale, field experiments will be used to measure nitrogen transformation and removal rates as a function of flow rate and in-canopy vegetation structure. Net nitrogen removal rates at canopy and reach scales will be compared via a modeling approach to determine whether local-scale interactions can explain net patterns in nitrogen removal. This project additionally seeks to promote water quality stewardship through an experiential, communication focused educational initiative and student led outreach activities while increasing student diversity. Educational activities will be structured to first build university student expertise via active learning in courses then have the students teach what they have learned through a local science center and its successful existing outreach program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.