عنوان مقاله [English]
Background and objectives: Urmia Lake drying up and withdrawal of its shores resulted in remaining of vast saline lands around it. The study of soils as the indicator of the environmental condition, in which they have developed, can provide valuable information about the past climate of the area. The aim of this research was to study the evidence of the Urmia Lake fluctuations through the developed soils in its Southeastern shore.
Materials and methods: a transect perpendicular to Urmia Lake was studied in southeast Urmia Lake, in Bonab Plain. Seven pedons based on the variation of geomorphic surfaces and landscape change, were described and sampled along a transect next to the southeastern shore of Urmia Lake. Soil samples were collected from all diagnostic horizons and analyzed for some of their physicochemical characteristics. From some of the diagnostic horizons, undisturbed samples were gathered for micromorphological analysis. Clay mineralogy was also performed for some of the horizons.
Results: Results showed that among studied soil pedons, pedons 1, 2, 3, 4, and 5 had saline soils along with buried horiozons and their developments were mostly affected by Urmia Lake sediments and fluctuations. In all of these 5 soil pedons, buried soils with different degrees of development were detected, which showed that these soils had been exposed during different time periods, before further burial by lacustrine sediments. Buried soils in first 3 pedons had more developed soils than their upper soils, showing that upper soils are in their early stages of development. micromorphological study of buried Bk horizon in the depth of 50-105 cm of P2, revealed that it is a highly pedal and highly separated horizon with calcite coatings and infillings. Based on the results, no evidence of buried soils or lacustrine sediments was observed in pedon 6, which was located in agricultural lands, 1 km from pedon 5. In pedon 6, highly developed calcic horizons were observed, showing that this part of landscape has been stable for a long time, at least longer than other 5 studied pedons.
Conclusion: The existence of buried soils and textural discontinuities in some of the studied soil pedons showed that Urmia Lake had several fluctuations due to climatic changes and had also been much more extended than that of 1998 in the past. The study also revealed that its recession has happened during several stages which has also coincided with several expansions and consequent sedimentations, through which, soil evolution and development in its southeastern shore has affected.