Nutrient Mobilization Following Winter Fires in an Irregularly Flooded Marsh

Abstract

AbstractThe effects of prescribed winter burning on nutrient pools in an irregularly flooded marsh in St. Louis Bay, Miss., were investigated. Nutrient levels were determined in field‐collected pre‐fire vegetation, post‐fire regrowth, pre‐fire and post‐fire sediments, combustion residues, and reference materials from unburned adjacent sites. Post‐fire soil chemistry was characterized by transitory elevation of sediment‐water pH, P extractable in 0.10N HCl + 0.03N NH4F, and exchange + solution phase K, Ca, and Mg in surface sediments. Although input of ash‐borne nutrients into the marsh appeared minimal for most elements, estimated losses of N and K from combustible plant matter exceeded 90 and 50%, respectively, for both vegetation communities examined, one dominated by needle rush (Juncus roemerianus Scheele), and the other by giant cordgrass (Spartina cynosuroides (L.) Roth). Losses of these elements in standing elemental pools amounted to 70% for N and nearly 40% for K within both communities. Increases in both absolute elemental concentrations and elemental standing stocks in early spring regrowth, particularly with respect to N, appeared associated with marsh burning. Stimuli including slight increases in some elements in the sediments, sediment warming, and increased insolation, may have contributed to the higher nutrient levels found in plants from burned areas, although a slight lag in physiological ages of plants within burned and reference sites may account for observed differences.