Canopy influences of five range plant species on the redistribution of chemical forms of iron in a calcareous soil

Abstract

Iron (Fe) deficiency is common in calcareous soils of southern Iran. Chemical forms of Fe in a calcareous soil were studied in the beneath and the interspace soils of five common range plant species. Results showed that electrical conductivity (EC) and organic matter (OM) content was significantly higher in the soil beneath canopies as compared to interspace soil. The reverse was true for pH of the soil except in case of Salvia compressa. Among different forms of Fe, soluble and exchangeable Fe (SolEx-Fe) form was higher in the soil beneath canopy of all plant species as compared to interspaces. Similar results were recorded for Fe bound to organic materials (Om-Fe) but only in the case of Convolvulus argyracanthus, Echinops glanduloso-punctatus, and Centaurea intricata.In the soil beneath Convolvulus argyracanthus and Centaurea intricata canopies Fe bound to manganese (Mn) oxides (Mnox-Fe) was significantly higher but the amount of residual Fe (Res-Fe) was lower compared to the interspace soil. A reverse trend was, however, observed in the case of Teucrium polium, demonstrating differential distribution of Fe forms at the two locations. The summation of reactive Fe forms [SolEx-Fe, Fe bound to carbonates (Car-Fe), and Om-Fe] known as readily or potentially available Fe was higher in the soil under canopies than in interspace soils. It is assumed that the higher contents of OM and lower values of pH enhanced Fe availability in the soil under plant canopies in comparison with interspace soil.