Gypsification Processes and Porosity Changes in Soils from Southern Iran (Jooyom Region-Fars Province)1

摘要

Population growth are leading to intensive and extensive land use even in gypsiferous and gypseous soils which resulted in a greater demand for information of these common soils. The soils of Jooyom region located in southern Iran were studied in order to estimate the rates of soil formation processes, such as gypsum accumulation, and how they affect soil porosity. Soils have gypsum contents ranging from 0.02 to 42.1%, which increases with depth. In the field, gypsum accumulations are described as powdery nodules and vermiform gypsum. Different kinds of micromorphological pedofeatures related to gypsum are observed, which include infillings and coatings of gypsum crystals, typic nodules and crystal twins. Nodules of micrite pseu-domorphs after lenticular gypsum are found, where calcite has substituted the original gypsum, which are indicators of a more arid climate in the past, followed by a more humid one. The extent, morphology and size of gypsum crystals depend on the pedogenic processes. In regard to micromorphological classification of gypsiferous soil materials, they are classified in two groups of Eogypsic and Gypsic. Soil porosity changes related to gypsum accumulation were studied and quantified by image analysis. The understanding the retention and movement of water and air in the soil; therefore, these results have a practical importance for land use and management of gypsiferous soils.