LTREB: Aboveground biomass, plant density, annual aboveground productivity, plant heights and snail observations in control and fertilized plots in a Spartina alterniflora-dominated salt marsh, North Inlet, Georgetown, SC: 1984-2025

Aboveground biomass and plant density were measured non-destructively as a component of a long-term project seeking to understand how salt marsh primary production and sediment chemistry respond to anthropogenic (e.g. eutrophication) and natural (e.g. sea-level rise) environmental change. Feedbacks between plants, sediments, nutrients and flooding were investigated with particular attention to mechanisms that keep marshes in equilibrium with sea level. Biomass was calculated from plant height measurements using allometric equations. Annual productivity was calculated from approximately-monthly biomass estimates. In addition to plant height measurements, observations of snails in sample plots were recorded.
Other data collected as part of the project include marsh surface elevation and porewater nutrient concentrations. These data have been used to develop the Marsh Equilibrium Model, an important tool for coastal resource managers.
Sampling occurred at Spartina alterniflora-dominated salt marsh sites in North Inlet, a relatively pristine estuary near Georgetown, SC on the SE coast of the United States. North Inlet is a tidally-dominated, bar-built estuary, with a semi-diurnal mixed tide and a tidal range of 1.4m. The 25-km2 estuary is comprised of about 20.5 km2 of intertidal salt marsh and mudflats, and 4.5 km2 of open water. Sampling began at one location in 1984, and at three additional locations in 1986. Sampling occurred approximately monthly through 2025. The study is on-going.
There are four sampling locations at two sites. Two locations are in the low marsh; two locations are in the high marsh. One high marsh location had control sampling plots in addition to plots fertilized with nitrogen and phosphorus.

本数据集隶属于一项长期研究项目，该项目旨在探究盐沼初级生产力与沉积物化学特征如何响应人为干扰（例如富营养化（eutrophication））及自然（例如海平面上升（sea-level rise））环境变化。研究以非破坏性方式测定地上生物量与植株密度，针对植物、沉积物、营养物质与潮汐淹涝之间的反馈关系展开调查，并重点关注维持盐沼与海平面保持平衡的相关机制。生物量通过株高测量数据结合异速生长方程（allometric equations）计算得到；年度生产力则基于约每月一次的生物量估算结果推算得出。除株高测量外，研究人员还记录了样地内蜗牛的观测数据。

本项目还采集了盐沼地表高程与孔隙水营养盐浓度（porewater nutrient concentrations）等相关数据。上述数据已被用于开发盐沼平衡模型（Marsh Equilibrium Model），该模型是面向海岸资源管理者的重要实用工具。

采样工作于美国东南海岸南卡罗来纳州乔治敦附近的北因莱特定河口（North Inlet）开展，该区域的盐沼样地以互花米草（Spartina alterniflora）为优势物种。北因莱特定河口属于潮汐主控型沙洲封闭河口，具有半日混合潮特征，潮差达1.4米。该河口总面积为25平方千米，其中约20.5平方千米为潮间带盐沼与潮滩，剩余4.5平方千米为开阔水域。采样工作于1984年在1个采样点位启动，1986年新增3个采样点位，截至2025年保持约每月一次的采样频率，目前该研究仍在进行中。

本次研究共设置2个样区、4个采样点位：2个位于低潮沼带，2个位于高潮沼带。其中1个高潮沼带采样点位除设置对照样地外，还布设了施加氮、磷肥料的处理样地。