Coastal wetlands, such as marshes and mangroves, provide many valuable ecosystem services and are vulnerable to climate change and anthropogenic impacts. Marshes are dominant in temperate regions and mangroves within the tropics; both plant types co-occur in subtropical ecotones. Dynamics within marsh-mangrove ecotones may be linked in part to local environmental drivers like nutrient enrichment. Previous studies within monospecific marsh and mangrove stands have reported increases in productivity in response to fertilization; however, the allocation of excess nutrient resources within co-occurring stands of mature plants is not well understood. To investigate nutrient dynamics within the marsh-mangrove ecotone, we fertilized naturally co-occurring Spartina alterniflora and Avicennia germinans stands (the dominant marsh and mangrove species, respectively) within the Gulf of Mexico. After four growing seasons of continuous enrichment, above- and belowground biomass were 2.5 and 1.5 times greater, respectfully, in enriched plots for A. germinans; S. alterniflora biomass did not differ between enrichment treatments. Mangrove leaves indicated a large nutrient response with altered leaf stoichiometry, larger surface area, and greater SPAD (proxy for chlorophyll a) in enriched plots. The fertilization effects may suggest A. germinans has a greater ability to acquire and allocate excess nutrients into productivity and biomass, relative to S. alterniflora, and may therefore, be the superior competitor for nutrient resources. In monospecific stands, both marsh and mangroves species have a high potential for nutrient uptake, but when they are co-occurring in the marsh-mangrove ecotone, nutrient retention may be more linked to mangrove ability to partition nutrient resources into various above- and belowground components. Global climate changes are driving mangrove coverage poleward into temperate salt marshes, expanding the areal extent of marsh-mangrove ecotones. At a local scale, these findings reveal that this mangrove expansion may be accelerated by anthropogenic nutrient input.

沼泽和红树林等沿海湿地提供了许多有价值的生态系统服务，并且容易受到气候变化和人为影响的影响。沼泽在热带地区的温带地区和红树林中占主导地位。两种植物类型同时出现在亚热带过渡带中。沼泽-红树林过渡带内的动态可能部分与当地环境驱动因素（如营养富集）相关。以前在单种沼泽和红树林林中进行的研究报告说，由于施肥，生产力提高了。但是，对成熟植物同时存在的林分内多余营养资源的分配知之甚少。为了研究沼泽-红树林过渡带内的营养动态，我们对天然共生的互花米草和紫花vic草进行了施肥在墨西哥湾内立（分别是主要的沼泽和红树林物种）。在连续富集四个生长季节之后，分别在富集的农杆菌中，地上和地下的生物量分别增加了2.5倍和1.5倍；互花米草的生物量在富集处理之间没有差异。红树林叶片在富集地块中指示了较大的养分响应，改变了叶片的化学计量比，更大的表面积和更大的SPAD（叶绿素a的代理）。施肥效应可能表明，相对于互花米链菌，A。菌种具有更大的能力来获取多余的营养并将其分配到生产力和生物量中，因此，可能成为养分资源的上佳竞争者。在单种林分中，沼泽和红树林物种都有很高的养分吸收潜力，但是当它们在沼泽-红树林过渡带中同时出现时，养分保留可能与红树林将养分资源分配到各种地上和地下的能力更多地相关。组件。全球气候变化正将红树林覆盖率带入温带盐沼，扩大了沼泽-红树林过渡带的面积范围。在当地范围内，这些发现表明，人为营养输入可能会促进红树林的扩张。