Factors and Processes of Soil Formation in Different Climates of Iran (A Review of Research in the Last Two Decades in the Soil Science Department of University of Tehran)

Accurate knowledge of soils and their classification plays a decisive role in the application of various management systems. The purpose of this study is to summarize some of the results of studies in the form of dissertations and articles extracted from them on the factors and processes of soil formation in different climates of Iran during the two last decades performed in different climates of the country in the Department of Soil Science and Engineering, University of Tehran. Variety of soil-forming factors including climate, parent materials, topography, vegetation, and time have led to the emergence of various characteristics and classes based on the Soil Taxonomy system. The predominant morphological traits in the studied soils in each study area, including the existing limitations and advantages, have been determined. In addition to soil classes, morphological, micromorphological, physical, chemical, clay mineralogy, organic and inorganic carbon storage, and geochemistry of formed soils are described in detail. Of the 12 soil categories in the American Classification System, at least 7 categories, and of the 32 reference groups of the WRB System, there are at least 16 reference groups in the study areas. The micromorphological results proved the effect of aeolian sediments on the soils formed on the basalt. Illite and chlorite in the clay mineralogy of many soils of the studied areas indicate that the studied soils are young. Smectite was found in slightly more developed soils (Vertisols and Aridisols). The formation of allophanes from pyroclastic materials is also a proof of the predominance of aluminum over silicon in the early stages of their aeration. Almost all soil-forming processes in this research were studied and discussed, and from an educational and research point of view, a clear view of the country's soils was shown.