Reduction of Natural Ferric Iron Chelators in Disturbed Forest Soils

Abstract

AbstractHydroxymate siderophores (HS) are high affinity FE3+ chelators which are produced and secreted into the soil by various soil microflora, including mycorrhizal fungi. HS are important in the iron nutrition of both the microorganisms which produce them and higher plants, and they may also protect higher plants from soil‐borne pathogens. We used a standard bioassay technique to compare HS concentrations in soils from 10 pairs of logged and adjacent unlogged sites in various areas of Oregon. In 8 of the 10 sites HS concentrations were significantly lower in soils from logged areas than in those from adjacent undisturbed forests. HS reductions were greater where slash was burned than where it was unburned or windrowed. Pot tests of soils from one site indicated that Douglas‐fir seedlings (Pseudotsuga menziesii [Mirb.] Franco) were iron limited in logged and burned but not in undisturbed forest soils. Soil pasteurization induced iron limitation in undisturbed soils, which suggests that iron limitation in soils from the logged and burned area may have been due to reduction of HS‐producing organisms.