ABSTRACT

The Qinghai-Tibet Plateau has developed immature soils since the late Pliocene period when it was uplifted. The objectives of this paper were (i) to investigate native major and trace elements of the immature soils in the Kekexili region in the Plateau; (ii) to evaluate the bioavailability of selected trace elements in the soils; (iii) to better understand the factors affecting accumulation and depletion of the elements and their bioavailability over a long history of alto-cryic pedogenesis. Cambosols and Aridosols are dominant soil types in this region while Gleyosols and Primosols are minor types. These coarse-textured soils have high soil pH and free carbonate content. The soil profile often developed a mattic or humic epipedon with high organic matter content in the topsoil. The contents of Ca, Mg, Na, and Sr in the Kekexili soils were significantly higher than the average values of Chinese soils, and also the world average, while the contents of Fe, Al, Ti, Mn, P, Co, Cr, and Ba in the former soils lower than those in the latter soils. The accumulation or depletion of elements was mainly dependent on soil carbonate content. The bioavailability of Fe, Zn, and Mn was positively related to the levels of organic matter in the surface soil. Results indicate that though these soils had a long history of pedogenesis, they were still relatively immature due to weak geochemical cycles but the bioavailability of nutrients in topsoil was high.