Nutrient Mobilization Following Winter Fires in an Irregularly Flooded Marsh

Abstract

The 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.

Wildland fire in ecosystems: effects of fire on soils and water

“…Increases in PO 4 and soil cations were attributed to ash deposition (Schmalzer and Hinkle 1992). In contrast, the results of winter burning of Juncus and Spartina marsh communities on the Mississippi Gulf Coast suggested that increases in extractable P were the result of mild heating of organic sediments, and the retention of ash-derived nutrients may be a function of meteorological factors, tidal regimes, and topography (Faulkner and de la Cruz 1982).…”

Soil dynamics following fire inJuncus andSpartina marshes

“…Such dif-ferences have been observed in previous studies. Faulkner and de la Cruz (1982) found that K increased immediately postburn in the Juncus marsh and remained high 1 mo later; a small K increase occurred 26 da postburn in Spartina that was greater 68 da postburn. Calcium increases were greater immediately postburn in Juncus than 1 mo later; Spartina marshes had high Ca values I and 2 mo postfire.…”

“…PO4-P increased immediately after fire in the Juncus and Spartina marshes studied by Faulkner and de la Cruz (1982) and remained elevated. Wilbur and Christensen (1983) found increased PO4-P through the first growing season postfire.…”

“…Burning changes the relationships between fixed and available nutrients; totals of some nutrients, particularly nitrogen, may be reduced by volatilization but available nutrients may increase (Raison 1979, Wells et al 1979, Faulkner and de la Cruz 1982. Vegetation removal results in changed site microclimate, particularly soil temperature regimes.…”

“…Fautkner and de la Cruz (1982) examined fire effects on soils of irregularly flooded Juncus roemerianus Scheele and Spartina cynosuroides (L.) Roth marshes. Wilbur and Christensen (1983) examined nutrient changes in peat soils of a pocosin after fire.…”