Collaborative Proposal: Coupled C, N and S cycling in coastal plain wetlands: how will climate change and salt water intrusion alter ecosystem dynamics?

滨海平原湿地在陆水、淡水和咸水的交汇处占有重要的景观地位。与所有湿地一样，沿海湿地在提供的服务方面与其所包含的区域相比具有不成比例的价值，包括养分转化、水净化和洪水控制。人类为了农业和林业而排干了东南部沿海平原的大部分湿地，从而削弱了它们提供营养和碳封存等关键生态系统服务的能力。与此同时，集约化肉类和家禽生产所产生的肥料和粪便大大增加了沿海生态系统的养分负荷。营养物负荷的增加和滞留量的减少造成了下游淡水和沿海生态系统的富营养化，从而导致了水质的退化和沿海渔业的衰退。气候变化可能会进一步加剧这些趋势：更高的温度和越来越多的零星降水可能会进一步缩小长期被淹没的湿地的空间范围，并已经导致干旱期间的季节性盐水入侵。预测沿海平原淡水可能的生态系统碳和营养循环进入一个更咸和越来越不确定的水文未来，需要对我们目前对淡水生态系统的理解进行重大改进。本研究从战略上关注了这一问题的两个方面：首先，将硫（来自海盐的~）动力学纳入我们对微生物如何改变碳和养分循环的理解中；其次，利用模拟建模将动态水文与微生物生物地球化学结合起来。自适应模拟建模与有针对性的实证工作将使我们能够快速测试和完善目前的湿地碳和养分循环模型，并将对湿地生物地球化学的新兴概念理解形式化为一个灵活、易于调整的建模框架。重点场地是北卡罗莱纳州沿海平原上的一个以前有沟渠和排水的农田，在2007年被恢复为河流湿地水文，成为东南部最大的私营缓解库。场地地形起伏很小（-1至+1米高程）；在夏季干旱期间，通过地表水混合经历显著的盐水入侵；并且有风潮驱动的水文，在时间和空间上产生硫浓度的大梯度。该场地代表了东南沿海平原农业景观的大片地区，这些地区正在积极恢复或废弃。该项目的经济和生态“成功”将受到整个地区监管机构和从业者的密切关注。这一研究项目将直接影响土地所有者在新兴生态系统服务市场上出售有效碳和营养信用额的潜力。由此产生的研究结果（连同其经济影响）将影响整个东南沿海平原未来的缓解和保护投资模式，并将提供关键信息，促进整个区域的气候适应规划。

Coastal plain wetlands occupy a critical landscape position at the intersection of terrestrial and aquatic and fresh and salt waters. Like all wetlands, coastal wetlands are disproportionately valuable in terms of services provided compared to the area they comprise including nutrient transformation, water purification, and flood control. Humans have drained wetlands throughout much of the southeastern coastal plain for agriculture and forestry, thus diminishing their capacity to provide critical ecosystem services such as nutrient and carbon sequestration. At the same time, fertilizer use and manure from intensive meat and poultry production have dramatically increased nutrient loading to coastal ecosystems. Increased loading and decreased retention of nutrients has caused eutrophication of downstream freshwater and coastal ecosystems, with the associated degradation in water quality and decline in coastal fisheries. Climate change may further exacerbate these trends: higher temperatures and increasingly sporadic precipitation may further diminish the spatial extent of perennially flooded wetlands and is already leading to seasonal salt water intrusion during drought. Predicting the likely ecosystem carbon and nutrient cycling of coastal plain freshwaters into a saltier and increasingly uncertain hydrologic future requires significant improvements to our current understanding of freshwater ecosystems. This proposal focuses strategically on two aspects of this problem: first, incorporating sulfur (~from sea salt) dynamics into our understanding of how microbes alter carbon and nutrient cycling and second, utilizing simulation modeling to mesh dynamic hydrology together with microbial biogeochemistry. Adaptive simulation modeling together with targeted empirical work will allow us to rapidly test and refine current models of wetland carbon and nutrient cycling and to formalize the emerging conceptual understanding of wetland biogeochemistry into a flexible, easily adjusted modeling framework. The focal field site is a formerly ditched and drained agricultural field in North Carolina's coastal plain that was restored to riverine wetland hydrology in 2007, becoming the largest privately owned mitigation bank in the southeast. The site has very little topographic relief (-1 to +1 m elevation); experiences significant salt water intrusion via surface water mixing during summer droughts; and has wind tide driven hydrology that generates large gradients in sulfur concentrations in both time and space. The field site is representative of large areas of SE coastal plain agricultural landscapes that are being actively restored or abandoned. The economic and ecological "success" of this project will be closely watched by regulators and practitioners throughout the region. This research program will directly affect the potential for site owners to sell validated carbon and nutrient credits in emerging ecosystem service markets. Resulting research findings (together with their economic implications) will influence future patterns of mitigation and conservation investment throughout the southeastern coastal plain and will provide critical information that will facilitate climate adaptation planning throughout the region.