LTREB Renewal: Long Term Studies of Salt Marsh Primary Production

盐沼是地球上最多产的环境之一，它们的价值很高，因为它们为许多具有商业价值的物种提供了食物和栖息地，它们改善了水质，缓冲了建筑物和其他基础设施，抵御了沿海风暴，它们为野生动物创造了新的土地和栖息地。该项目建立在南卡罗莱纳北部入口河口数十年的盐沼脐草生产力研究的基础上，该研究对沼泽生产力的调节和维持盐沼与海平面平衡的反馈产生了新的见解。这项研究很重要，因为海平面正在加速上升，并有可能淹没这些生态系统。该项目将采用实验和实地观测相结合的方法，了解随着海平面上升，日益增长的脐带草根系如何影响沼泽表面的高度。肥料的添加将用于促进根系生长，并测试这将使沼泽表面上升的假设。这些模拟沼泽海拔变化的操作将为相对海拔如何影响植物生长提供直接测试。这项研究将进一步为沿海资源管理者开发一个重要的管理工具——沼泽平衡模型。自1984年以来，北入口的LTREB研究包括每月测量沼泽草（互花米草）的茎数和高度，并补充了每月测量孔隙水化学、蜗牛密度和沼泽表面海拔。对这些数据的综合导致了沼泽平衡理论和沼泽平衡模型的发展，该模型描述了植物、营养物质、潮汐洪水和沉积物之间的反馈如何使沼泽与海平面达到平衡。在接下来的五年中，该项目将继续发展理论，继续收集原始数据，并进行实验操作，以测试植物根系和营养物质对沼泽海拔的重要性。据推测，营养物的添加会增加根系的生长，从而提高沼泽的平衡海拔。通过对沉积物岩心进行计算机断层扫描前后，再加上对沼泽表面高度的测量，在田间地块恢复氮和磷处理，将测试营养物质对地下生产和沉积物捕获对垂直增加的相对重要性的影响。利用沼泽器官进行的生物测定实验将直接检验生产力提高假说，并将与实地观察同时进行。通过向民间团体介绍海平面上升和沼泽问题，与决策者进行讨论，以及参与政策论坛，该项目的广泛影响将扩大到公众。支持研究生培训和访问学者利用北汊盐沼的长期施肥和普查地块。

Salt marshes are among the most productive environments on earth and they are highly valued because they provide food and nursery habitat for numerous species of commercial importance, they improve water quality, they buffer buildings and other infrastructure against coastal storms, and they create new land and habitat for wildlife. This project builds on decades of research in North Inlet estuary in South Carolina on the productivity of salt marsh cord grass that have led to new insights about the regulation of marsh productivity and the feedbacks that maintain salt marshes in equilibrium with sea level. This research is important because sea level is rising at an accelerating rate and threatens to drown these ecosystems. This project will employ a combination of experiments and field observations to understand how increasing cord grass root growth impacts the elevation of the marsh surface as sea level rises. Fertilizer additions will be used to increase root growth and test the hypothesis that this will allow the marsh surface to rise. These manipulations to simulate changing marsh elevations will provide a direct test of how relative elevation affects plant growth. This research will further development of an important management tool, the Marsh Equilibrium Model, for coastal resource managers.LTREB research at North Inlet has included monthly measurements on permanent plots of stem counts and heights of marsh cord grass (Spartina alterniflora) made since 1984 and supplemented by monthly measurements of porewater chemistry, snail density, and marsh surface elevation. A synthesis of these data has led to the development of a marsh equilibrium theory and the Marsh Equilibrium Model describing how feedbacks among plants, nutrients, tidal flooding, and sediments move a marsh toward an equilibrium with sea level. During the next five years this project will continue development of theory, continue collection of primary data, and conduct experimental manipulations to test the importance of plant roots and nutrients on marsh elevation. It is hypothesized that nutrient additions will increase the growth of roots and thereby raise the equilibrium marsh elevation. A resumption of nitrogen and phosphorus treatments in field plots, with before and after computed tomography scans of sediment cores, coupled with measurements of marsh surface elevation will test the effects of nutrients on the relative importance of belowground production and sediment trapping to vertical accretion. Bioassay experiments using marsh organs will directly test the productivity-elevation hypothesis and will be conducted in parallel with the field observations. The broader impacts of this project extend to the public through talks given about sea level rise and marshes to civic groups, discussions with policy makers, and participation in policy forums. Graduate student training and use of the long-term fertilization and census plots in the salt marsh at North Inlet by visiting scholars will be supported.