Productivity, stability, and geomorphological evolution of New England salt marshes: Plum Island case study

沿海盐沼因其重要的生态功能和社会价值而广为人知，作为商业上重要的鱼类和贝类的栖息地和育儿场，以及作为风暴缓减，提供了巨大的价值。国家目前正在失去其沿海沼泽栖息地的大部分。几个因素，包括海平面上升速度的变化，影响着盐沼的消长。然而，近几个世纪以来，由于陆地用途的变化导致的沉积物供应的变化可能主导了新英格兰盐沼的演变。该项目涉及对沉淀层的检查，以调查这样一种假设，即该地区现有的大片沼泽是最近迅速发展起来的，与殖民砍伐森林相关的泥沙产量增加有关。如果这一假设是正确的，那么很可能在该地区(现在重新造林和开发的景观冲刷的沉积物较少)，沼泽目前正在维持一种不稳定的平衡，依赖于沼泽草持续的泥沙捕获和稳定影响。植被的影响有助于沼泽表面获得海拔，使其不会随着海平面的上升而消失。然而，加速海平面上升会增加与潮汐一起涌入和流出沼泽的水量，增加潮汐水流，并倾向于对交织在潮汐沼泽中的河网造成侵蚀。一个简化的计算机模型的初步实验表明，如果受到海平面高上升和/或泥沙输送减少的沼泽植被的干扰，这种侵蚀可能会横向蔓延，不可逆转地将沼泽变成开阔的水域。该项目将利用实地观测进一步发展该模型，并利用它来探索沼泽和潮汐网络是如何随着植被影响、潮流、海平面上升以及土地利用/泥沙供应的变化而演变的。其结果将在科学分支学科(从景观进化到严格的生态学研究)和社会问题(从减少风暴到土地使用管理)上产生相当广泛的影响。

Coastal salt marshes are well recognized for their important ecological functions and societal values, providing great value as habitat and nursery grounds for commercially important fin and shellfishes, and as storm abatement. The Nation is currently losing much of its coastal marsh habitat. Several factors, including changes in sea-level-rise rates, influence salt-marsh growth and decline. However, changes in sediment supply caused by changing terrestrial land uses may have dominated the evolution of New England salt marshes in recent centuries. This project involves examination of sediment layers to investigate the hypothesis that the existing extensive marshes in this region developed recently and rapidly, in response to the increased sediment yield associated with colonial deforestation. If this hypothesis is true, it is possible that in this region (which now has less sediment washing off of reforested and developed landscapes) marshes are presently maintaining a precarious balance, relying on the continued sediment-trapping and stabilizing influences of marsh grasses. The vegetation influence helps the marsh surface gain elevation so that it does not disappear as sea level rises. However, accelerating rising sea level increases the amount of water that floods into and out of the marshes with the tides, increasing tidal currents and tending to cause erosion in the channel networks that intertwine through tidal marshes. Preliminary experiments with a simplified computer model suggest that if vegetation is disturbed in a marsh subjected to high rates of sea-level rise and/or reduced sediment delivery, this erosion could spread laterally, irreversibly converting marsh to open water. This project will employ field observations to further develop the model, and use it to explore how marshes and tidal networks evolve as vegetation influences, tidal currents, sea-level rise, and changing land use/sediment supply all interact. The results will have considerable broader impact across both scientific subdisciplines (ranging from landscape evolution to strictly ecological studies) and societal issues (ranging from storm abatement to land-use management).