Experimental tree mortality does not induce marsh transgression in a Chesapeake Bay low-lying coastal forest

David Walters; Joel A. Carr; Alyssa Hockaday; Joshua A Jones; Eliza McFarland; Katya E. Kovalenko; Matthew L. Kirwan; Donald R. Cahoon; Glenn R. Guntenspergen

doi:10.3389/fmars.2021.782643

USGS · 70227007

Experimental tree mortality does not induce marsh transgression in a Chesapeake Bay low-lying coastal forest

David Walters·Joel A. Carr·Alyssa Hockaday·Joshua A Jones·Eliza McFarland·Katya E. Kovalenko·Matthew L. Kirwan·Donald R. Cahoon·Glenn R. Guntenspergen

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Abstract

Transgression into adjacent uplands is an important global response of coastal wetlands to accelerated rates of sea level rise. “Ghost forests” mark a signature characteristic of marsh transgression on the landscape, as changes in tidal inundation and salinity cause bordering upland tree mortality, increase light availability, and the emergence of tidal marsh species due to reduced competition. To investigate these mechanisms of the marsh migration process, we conducted a field experiment to simulate a natural disturbance event (e.g., storm-induced flooding) by inducing the death of established trees (coastal loblolly pine, Pinus taeda ) at the marsh-upland forest ecotone. After this simulated disturbance in 2014, we monitored changes in vegetation along an elevation gradient in control and treatment areas to determine if disturbance can lead to an ecosystem shift from forested upland to wetland vegetation. Light availability initially increased in the disturbed area, leading to an increase in biodiversity of vegetation with early successional grass and shrub species. However, over the course of this 5-year experiment, there was no increase in inundation in the disturbed areas relative to the control and pine trees recolonized becoming the dominant plant cover in the disturbed study areas. Thus, in the 5 years since the disturbance, there has been no overall shift in species composition toward more hydrophytic vegetation that would be indicative of marsh transgression with the removal of trees. These findings suggest that disturbance is necessary but not sufficient alone for transgression to occur. Unless hydrological characteristics suppress tree re-growth within a period of several years following disturbance, the regenerating trees will shade and outcompete any migrating wetland vegetation species. Our results suggest that complex interactions between disturbance, biotic resistance, and slope help determine the potential for marsh transgression.

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Frontiers in Marine Science Article

Source-reported bounding extent: 36.500805317604765° to 39.86758762451019° latitude; -77.508544921875° to -75.06958007812499° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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David Walters, Joel A. Carr, Alyssa Hockaday, Joshua A Jones, Eliza McFarland, Katya E. Kovalenko, Matthew L. Kirwan, Donald R. Cahoon, Glenn R. Guntenspergen. 2021-12-10. Experimental tree mortality does not induce marsh transgression in a Chesapeake Bay low-lying coastal forest. https://doi.org/10.3389/fmars.2021.782643

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