The George Washington University, NW, Washington, DC, USA.
Ann Bot. 2020 Feb 3;125(2):335-344. doi: 10.1093/aob/mcz133.
The capacity for dispersal to promote or hinder species' responses to global change remains a major question in ecology. One ecosystem experiencing rapid change is the tidal marsh, which is migrating inland in response to accelerated sea level rise. Few studies to date have investigated the ecological dynamics that impact this large-scale migration. Seed dispersal and persistence in the soil seed bank is a component that can be strongly indicative of community trajectories. With this in mind, the aim of our study was to characterize the germinable seed bank across a marsh-forest ecotone in the Chesapeake Bay.
Soil samples were collected across transects that ran from the high marsh to the coastal loblolly pine forest in a brackish marsh in Blackwater National Wildlife Refuge, MD, USA. Samples were grown in a greenhouse and watered with either freshwater or 3 ppt seawater solution. We compared community composition across transects and between salinity treatments. Additionally, we compared the seed bank with standing vegetation and used seed trait data from the TRY Database to investigate changes in functional traits along this ecotone.
We found halophytic species dispersing up to 15 m into the forest and a general lack of obligate upland species, including near absence of Pinus taeda, the dominant species in the forest canopy. A majority of species detected in the seed bank were wetland species of various types, with species with wide salinity tolerance arising most frequently. Salinity addition had a significant negative influence on seed bank diversity.
Overall, our seed bank results suggest that dispersal and germination under the conditions of saltwater intrusion will limit forest regeneration and favour marsh plant dispersal. This indicates that the ecological processes that determine the soil seed bank community will support continued migration of marsh species into uplands.
扩散能力是促进还是阻碍物种对全球变化的响应，这仍然是生态学中的一个主要问题。一个正在经历快速变化的生态系统是潮汐沼泽，它正在响应海平面加速上升而向内陆迁移。迄今为止，很少有研究调查过影响这种大规模迁移的生态动态。种子在土壤种子库中的扩散和存活是一个可以强烈指示群落轨迹的组成部分。考虑到这一点，我们的研究目的是描述切萨皮克湾黑水河国家野生动物保护区盐沼-森林生态交错带的可发芽种子库。
从高沼泽到美国马里兰州布拉克沃特国家野生动物保护区的咸沼沿海罗汉松林，沿样带采集土壤样本。将样品在温室中生长，并分别用淡水或 3 ppt 海水溶液浇水。我们比较了样带和盐度处理之间的群落组成。此外，我们将种子库与现有的植被进行了比较，并利用 TRY 数据库中的种子性状数据，研究了功能性状沿这个生态交错带的变化。
我们发现盐生植物的传播距离可达 15 米，进入森林，而几乎没有必需的旱地物种，包括在森林冠层中占主导地位的 Pinus taeda。种子库中检测到的大多数物种是各种湿地物种，具有广泛耐盐性的物种最为常见。盐度增加对种子库多样性有显著的负面影响。
总的来说，我们的种子库结果表明，在海水入侵条件下的扩散和萌发将限制森林再生，并有利于沼泽植物的扩散。这表明，决定土壤种子库群落的生态过程将支持沼泽物种向高地的持续迁移。
