Coastal salt marshes, which provide valuable ecosystem services such as flood mitigation and carbon sequestration, are threatened by rising sea level. In response, these ecosystems migrate landward, converting available upland into salt marsh. In the coastal-plain surrounding Chesapeake Bay, USA, conversion of coastal forest to salt marsh is well-documented and may offset salt marsh loss due to sea level rise, sediment deficits, and wave erosion. Land slope at the marsh-forest boundary is an important factor determining migration likelihood, however, the standard method of using field measurements to assess slope across the marsh-forest boundary is impractical on the scale of an estuary. Therefore, we developed a general slope quantification method that uses high resolution elevation data and a repurposed shoreline analysis tool to determine slope along the marsh-forest boundary for the entire Chesapeake Bay coastal-plain and find that less than 3% of transects have a slope value less than 1%; these low slope environments offer more favorable conditions for forest to marsh conversion. Then, we combine the bay-wide slope and elevation data with inundation modeling from Hurricane Isabel to determine likelihood of coastal forest conversion to salt marsh. This method can be applied to local and estuary-scale research to support management decisions regarding which upland forested areas are more critical to preserve as available space for marsh migration.

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使用地理空间技术量化边坡作为森林向沼泽转化的驱动力：在美国切萨皮克湾沿海平原的应用

沿海盐沼受到海平面上升的威胁，提供了宝贵的生态系统服务，例如减灾和固碳。作为响应，这些生态系统向陆地迁移，将可用的高地转变为盐沼。在美国切萨皮克湾周围的沿海平原上，沿海森林向盐沼的转化已有充分记录，并可以抵消由于海平面上升，沉积物缺乏和波浪侵蚀而造成的盐沼损失。沼泽-森林边界的坡度是决定迁移可能性的重要因素，但是，使用野外测量来评估跨越沼泽-森林边界的坡度的标准方法在河口规模上是不切实际的。所以，我们开发了一种通用的坡度量化方法，该方法使用高分辨率高程数据和重新设计的海岸线分析工具来确定整个切塞皮克湾沿海平原沿沼泽森林边界的坡度，发现少于3％的样带的坡度值小于超过1％；这些低坡度的环境为森林向沼泽的转化提供了更有利的条件。然后，我们将海湾地区的坡度和海拔数据与伊莎贝尔飓风的淹没模型相结合，以确定沿海森林转化为盐沼的可能性。该方法可以应用于本地和河口规模的研究，以支持有关哪些陆地林区作为沼泽迁移的可用空间保存更为关键的管理决策。