EDI Staging Environment
Woody encroachment is occurring in many marsh-mangrove ecotones across the globe, with multiple drivers contributing to an increase in mangrove cover. As a result, marsh plant species are often displaced, resulting in a striking regime shift from grass and forb-dominated habitats to taller, woody vegetation. Our goal was to quantify the bottom-up effects of mangrove woody encroachment into coastal wetlands on associated plant and epifaunal assemblages. In 2012, we established several large (> 20 ha) survey areas at tidal wetland sites with or without black mangroves (Avicennia germinans) on the Texas (USA) coast in the Gulf of Mexico, an area highly susceptible to mangrove encroachment. Starting in 2012, we annually recorded vascular plant cover and diversity and recorded snail (Littoraria irrorata) and fiddler crab (Uca spp.) density along transects perpendicular to the shoreline. Marsh plant species richness was 50% lower at sites with mangroves, and some species, such as Sarcocornia spp. and Distichlis spicata, were relatively rare or absent from sites with mangroves. The wetland plant communities at these sites were relatively unaffected by Hurricane Harvey (August 2017). Epifaunal snails and crabs were common at all sites, with abundances that varied over time. Our results indicate that coastal wetlands dominated by mangroves support different and lower diversity plant assemblages than marsh-dominated areas. These results were largely consistent with the results of a previous manipulative experiment in the same area. Therefore, as woody encroachment continues and mangrove cover gradually increases, this change may lead to complex bottom-up effects on a range of ecosystem processes and services.
EDI is a collaboration between the University of New Mexico and the University of Wisconsin – Madison, Center for Limnology:
