Bickford, W.A.; Needelman, B.A.; Miller, M.W., and Hutchins, E.G., 2015. Prescribed fire increases soil temperatures through canopy removal in a Mid-Atlantic brackish marsh.Canopy removal produced by prescribed fire may influence soil temperatures, which has the potential to affect conditions for plant growth and other temperature-related soil functions. We assessed the changes in soil temperatures following prescribed fire using manipulative treatments in a brackish tidal marsh in the Blackwater National Wildlife Refuge in Dorchester County, Maryland, using two randomized complete block experiments. At No-Burn sites, treatments were canopy removal through clipping and ash/biochar deposition. At Annual Burn sites, the treatment was canopy replacement using a constructed frame and senesced vegetation. Soil temperatures were continuously measured over a period of 6 months (one growing season). Ash/biochar deposition did not affect soil temperatures. Mean daily soil temperatures at a depth of 5 cm were as much as 2°C higher in plots with canopy removal at the No-Burn sites and as much as 2.9°C lower in plots with replaced canopies at the Annual Burn sites. Canopy removal was also associated with increased soil temperatures at the 20-cm depth. Soil temperature effects were lower during a period of high water levels early in the season than they were during a mid-season period with lower water levels. Prescribed fire causes increases in soil temperatures through canopy removal and therefore may positively influence plant productivity in species that can take advantage of an earlier growing season and/or higher growing season temperatures.