LTREB: Aboveground biomass, plant density, annual aboveground productivity, and plant heights in control and fertilized plots in a Spartina alterniflora-dominated salt marsh, North Inlet, Georgetown, SC: 1984-2021

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 2021. 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.本数据集作为一项长期研究项目的组成部分，以非破坏性方式测定地上生物量与植物密度，旨在探明盐沼初级生产力及沉积物化学特征如何响应人为（如富营养化）与自然（如海平面上升）环境变化。研究聚焦于植物、沉积物、营养物质与潮汐淹水之间的反馈机制，尤其关注维持盐沼与海平面处于平衡状态的作用机理。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；年初级生产力则基于约每月一次的生物量估算值计算得出。除株高测量外，研究人员还记录了样地内螺类的观测数据。 本项目采集的其他数据还包括盐沼表面高程与孔隙水营养盐浓度。上述数据已被用于开发盐沼平衡模型（Marsh Equilibrium Model），该模型是海岸资源管理者的重要辅助工具。 采样工作在美国东南海岸南卡罗来纳州乔治敦附近一处相对原始的河口——北因列特（North Inlet）的互花米草（Spartina alterniflora）主导盐沼样地开展。北因列特属于潮汐主导型沙坝河口，具有半日混合潮型，潮差为1.4米。这片面积25平方千米的河口区域包含约20.5平方千米的潮间带盐沼与泥滩，以及4.5平方千米的开阔水域。 采样工作于1984年在一处点位启动，1986年新增3处采样点位，此后至2021年基本保持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处样地、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处高潮沼带采样点位除设置对照样地外，还设置了施加氮、磷肥料的处理样地。