Iron oxide mineralogy of Terre Rosse and Rendzinas in relation to their moisture and temperature regimes

Abstract

SummaryTerre Rosse and Rendzinas occur on limestones close together under the same climatic conditions. Their differences in iron oxide mineralogy are believed to be due to differences in the pedoclimate. We monitored the soil moisture tension and the soil temperature over nearly 3 years in Terra Rossa‐Rendzina pairs on hard limestone and soft chalk in Israel. The Terre Rosse dried out more rapidly than the Rendzinas mainly because of their smaller water‐holding capacity. In summer, average soil temperatures in the Rendzinas were significantly lower than in the Terre Rosse.Haematite dominates the red Terre Rosse and goethite the yellower Rendzinas. This difference appears to be related to the soil climate, specifically the moisture regime of the two soils, and supports the hypothesis that release of Fe and formation of ferrihydrite in Terre Rosse during the wet winter is followed by transformation to haematite during marked desiccation in the dry summer. By contrast, wetter soil conditions in the Rendzinas direct the formation of Fe oxides more towards goethite. either directly or by transformation of ferrihydrite via solution.