Abstract: In this paper, the biological and non-biological characteristics of biotic crusts on Shapotou sand dunes fixed with artificial vegetations were investigated, and the method of using time as the substitute of space was applied to study the development and succession patterns of the crusts. The results showed that the biotic crusts had a rapid soil formation process. Along with the duration of dune fixation, the thickness of the crusts and the clay content in them increased, while the bulk density showed a declining tendency. Lichen, algae, and moss were the dominant biotic species, and the formation and development of the crusts was also an important biological process. The development of the crusts involved the interactions between biotic and abiotic components during sand fixation, and was also a process of clay accumulation, biotic species development, and soil formation. A qualitative classification of three development stages of the crusts was summarized, based on the characteristics of their genesis.

Key words: Yuanjiang savanna valley, Leaf anatomical features, Leaf nutrient concentrations