Effects of Fire on Nutrient Concentrations and Standing Crops in Biomass of Juncus roemerianus and Spartina bakeri Marshes

摘要

We examined effects of fire on nutrient concentrations and standing crops in Juncus roemerianus and Spartina bakeri marshes by sampling biomass from 25 plots (0.25 sq m) in each marsh before and one year after a fire, separating samples by taxon and live or standing dead categories, and analyzing for Total Kjeldahl Nitrogen (TKN), P, K, Ca, and Mg. Nitrogen concentrations were lower in all biomass types one year after burning. Phosphorus concentrations increased in live Spartina, decreased in live Juncus and live Sagittaria in the Juncus marsh, and were unchanged in other types; however, the ratio of P to N increased in all live biomass types. Concentrations of K declined or remained unchanged. Calcium concentrations increased in Juncus and Spartina. Magnesium concentrations decreased in live and dead Juncus (Juncus marsh), but increased in live Sagittaria (Juncus marsh), dead Sagittaria (Spartina marsh), and live Spartina. Live biomass generally had higher concentrations of N, P, and K but lower levels of Ca than dead biomass. Standing crops of all nutrients were much lower than one year after fire than preburn. Our results differ from the increases in many tissue nutrients recorded soon after fire in other studies. Nutrient concentrations often decline with tissue age; thus, concentrations one year postburn may have differed from those immediately postburn. The absence of an increase in available soil N until six months postburn may have limited N concentrations in regrowing biomass. Standing crops of biomass and nutrients did not reestablish preburn levels in these marshes in one year.