Coastal marshes provide essential ecosystem services related to biodiversity, water quality, and protection from erosion. As increasing rates of relative sea-level rise affect many coastal marsh systems, a thorough understanding of marsh responses to sea-level change, particularly the migration of marsh–upland boundaries, becomes essential. The goal of this study was to determine precise elevation thresholds associated with coastal marsh, the marsh–upland ecotone, and upland plant communities along Mississippi’s Gulf of Mexico coast (diurnal, microtidal). Elevations (NAVD88) were measured using survey-grade Global Navigation Satellite System solutions integrated with high-precision leveling. Plant species were sampled at approximately 1-m intervals along each of thirty-three transects extending from intermediate marsh through the marsh–upland ecotone. Elevation thresholds associated with plant community change were determined based on relevant quartiles of the data. Probabilities of occurrence of each plant community type were computed for elevations at the centimeter scale. Results indicated transitions from marsh to ecotone and ecotone to upland at elevations of approximately 0.40 m and 0.60 m, respectively. Understanding the precise nature of these centimeter-scale dependencies of marsh vegetation on coastal elevation will facilitate spatial modeling of marsh transgression in response to sea-level rise, subsidence, changes in sediment flux, and land use change.

沿海沼泽提供与生物多样性、水质和免受侵蚀有关的基本生态系统服务。随着相对海平面上升速度的增加影响许多沿海沼泽系统，彻底了解沼泽对海平面变化的反应，特别是沼泽 - 高地边界的迁移，变得至关重要。本研究的目的是确定与密西西比州墨西哥湾沿岸的沿海沼泽、沼泽-高地交错带和高地植物群落（昼夜、微潮）相关的精确海拔阈值。海拔高度 (NAVD88) 是使用与高精度水准仪集成的测量级全球导航卫星系统解决方案测量的。沿着从中间沼泽延伸到沼泽-高地交错带的三十三个样带中的每一个，以大约 1 米的间隔对植物物种进行采样。根据数据的相关四分位数确定与植物群落变化相关的海拔阈值。以厘米尺度计算每种植物群落类型的发生概率。结果表明，在海拔分别约为 0.40 m 和 0.60 m 时，从沼泽过渡到交错带，从交错带过渡到高地。了解沼泽植被对海岸高程的这些厘米级依赖性的精确性质将有助于对响应海平面上升、沉降、沉积物通量变化和土地利用变化的沼泽海侵进行空间建模。根据数据的相关四分位数确定与植物群落变化相关的海拔阈值。以厘米尺度计算每种植物群落类型的发生概率。结果表明，在海拔分别约为 0.40 m 和 0.60 m 时，从沼泽过渡到交错带，从交错带过渡到高地。了解沼泽植被对海岸高程的这些厘米级依赖性的精确性质将有助于对响应海平面上升、沉降、沉积物通量变化和土地利用变化的沼泽海侵进行空间建模。根据数据的相关四分位数确定与植物群落变化相关的海拔阈值。以厘米尺度计算每种植物群落类型的发生概率。结果表明，在海拔分别约为 0.40 m 和 0.60 m 时，从沼泽过渡到交错带，从交错带过渡到高地。了解沼泽植被对海岸高程的这些厘米级依赖性的精确性质将有助于对响应海平面上升、沉降、沉积物通量变化和土地利用变化的沼泽海侵进行空间建模。结果表明，在海拔分别约为 0.40 m 和 0.60 m 时，从沼泽过渡到交错带，从交错带过渡到高地。了解沼泽植被对海岸高程的这些厘米级依赖性的精确性质将有助于对响应海平面上升、沉降、沉积物通量变化和土地利用变化的沼泽海侵进行空间建模。结果表明，在海拔分别约为 0.40 m 和 0.60 m 时，从沼泽过渡到交错带，从交错带过渡到高地。了解沼泽植被对海岸高程的这些厘米级依赖性的精确性质将有助于对响应海平面上升、沉降、沉积物通量变化和土地利用变化的沼泽海侵进行空间建模。