We established a long-term field experiment in 2012. Ten large 24m (parallel with the channel) x 42m (perpendicular to the channel) plots were demarcated and thinned to create mangrove densities varying from 0% to 100% in increments of 11 percent (0%, 11%, 22%, 33%, 44%, 55%, 66%, 77%, 88%, and 100%) to mimic effects of mangrove dieback following a hard freeze. These plots run perpendicular to the Lydia Ann shipping channel. Each large plot was divided into 112 cells, each 3 x 3m. To create the gradient of mangrove cover, individual cells either had aboveground mangrove biomass removed or left intact to create patches in which mangroves were present or absent. Thinning was completed in a stratified random checkerboard pattern, and we allowed the natural colonization of salt marsh vegetation in the cleared areas. The manipulated cells were maintained every 3-4 months. Three common marsh plants, Spartina alterniflora, Batis maritima, and Sarcocornia sp. were transplanted into eight of the plots (we did not use the 0 and 100 % mangrove plots) on March 13-15, 2013 and harvested in November 2013. All three species were planted together in single 3 x 3 m cells, but far enough apart that their canopies did not overlap. Plants were transplanted into 3 x 3 m cells in which mangroves were completely removed, in which aboveground biomass was removed but pneumatophores were present, and in which mangroves were present both above and belowground. There were four replicates of each treatment per plot. At the end of the growing season, on November 20, 2013, above-ground biomass of each transplanted plant was harvested, dried at 60 degrees C for four days, and weighed.
