Duke University Department of Biology, Durham, NC, USA.
North Carolina State University Department of Forestry and Environmental Resources, Raleigh, NC, USA.
Ann Bot. 2020 Feb 3;125(2):255-264. doi: 10.1093/aob/mcz039.
Coastal plant communities globally are highly vulnerable to future sea-level rise and storm damage, but the extent to which these habitats are affected by the various environmental perturbations associated with chronic salinization remains unclear. In this study, we examine the relationship between North Carolina wetland tree community composition and basal area change and indicators of salinization such as soil salt ion content and elevation.
We surveyed 34 forest plots in forested, freshwater wetlands across the Albemarle-Pamlico Peninsula. A subset of our study sites had been sampled during the previous decade as part of the Carolina Vegetation Survey, enabling us to investigate the environmental effects on current community structure, and community change over time.
Multi-variate (ordination) analysis and linear regression models of tree community composition revealed that elevation and soil salt content were correlated with changes in total site tree basal area. Shifts in tree community composition were, however, only weakly correlated with indicators of salinization, specifically elevation, soil sulphate and sodium, but not chloride. While the majority of plots experienced gains in basal area over the past decade, consistent with secondary succession, sites with high soil salt content or low elevation experienced basal area (biomass) loss during the same period.
The key factors associated with chronic saltwater intrusion (soil ion content) likely explain recent changes in tree biomass, and potential shifts in community composition in low-elevation sites along the North Carolina coast. Not only is it probable that other coastal forest ecosystems worldwide will experience similar stressors and shifts in community biomass and structure as sea levels rise, but the ability of these habitats to deliver key ecosystem services like carbon sequestration and flood defence will be compromised as a result.
全球沿海植物群落极易受到未来海平面上升和风暴破坏的影响，但这些栖息地受到与慢性盐渍化相关的各种环境干扰的影响程度尚不清楚。在这项研究中，我们研究了北卡罗来纳湿地树木群落组成与基面积变化之间的关系，以及土壤盐离子含量和海拔等盐渍化指标。
我们调查了阿勒格尼-帕姆利科半岛森林覆盖的淡水湿地中的 34 个森林样地。我们研究的一部分样地在前十年曾作为卡罗莱纳植被调查的一部分进行过采样，使我们能够研究环境对当前群落结构和群落随时间变化的影响。
树木群落组成的多元（排序）分析和线性回归模型表明，海拔和土壤盐分含量与总站点树木基面积的变化有关。然而，树木群落组成的变化与盐渍化指标的相关性很弱，具体来说，与海拔、土壤硫酸盐和钠有关，而与氯无关。虽然大多数样地在过去十年中基面积增加，与次生演替一致，但土壤盐分含量高或海拔低的样地在同一时期基面积（生物量）减少。
与慢性海水入侵（土壤离子含量）相关的关键因素可能解释了北卡罗来纳沿海地区树木生物量的近期变化，以及低海拔地区群落组成的潜在变化。不仅世界上其他沿海森林生态系统可能会像海平面上升一样经历类似的压力和群落生物量和结构的变化，而且这些栖息地提供关键生态系统服务（如碳封存和防洪）的能力也将因此受到影响。
