Effect of soil moisture regime on micromorphoogy of gypsum pedofeatures in soils of Fars province

Gypsum is an abundant soil mineral in arid and semiarid climates with low rainfall and gypsiferous parent material. Although gypsum is found over a wide range of temperatures, most gypsiferous soils are formed under xeric, ustic and aridic moisture regimes. This study was conducted in order to investigate the effect of soil moisture regimes on micromorphology of gypsum in gypsic and petrogypsic horizons of soils of Fars province. Micromorphological pedofeatures, including hypocoating, coating, loose continuous, dense complete and dense incomplete infilling of gypsum in voids and channels walls. Lenticular, prismatic, interlocked plates, pseudo-hexagonal and allabasrtin of gypsum crystals observed in thin sections. A clear relationship was noticed between gypsum morphology and soil moisture regime as well as soil depth. More diversity of gypsum crystals was found in subsurface horizons than surface horizons. Longer size of gypsum crystals were observed in subsurface horizons. Higher abundance of lenticular gypsum crystals were found in more developed soils. Higher quantity of prismatic, acicular, columnar and blade-like crystals was occurred in soils with lower rainfall and aridic moisture regime. Soils with lighter texture exhibited more diversity of gypsum crystals morphology. In addition, larger sizes of lenticular gypsum crystals with lower abundance were observed in more humid soils.