Abstract: Field investigation and microcosm experiment were conducted to study the dung beetle species composition and decomposition function in fresh horse dung pats in desert steppe of Inner Mongolia. A total of 13528 dung beetle individuals were collected, belonging to 26 species, 4 genera, and 3 families, among which, Aphodius comma was the dominant species, with its individual number occupying 88.5% of the total. The species composition of the beetle varied obviously in different seasons. In the fresh horse dung pats, endocoprids (Aphodius spp.) were dominated, with the species number and individual number being the highest within 3 days of fresh horse dung pats deposit and nearly disappeared after 6 days. After 136 days decomposition, 52.5% of the horse dung remained, and the release rates of N and P from the remained dung were lower than that of K. It was suggested that dung beetle affected the horse dung decomposition mainly through its activities in the dung, and the beetle’s activities and wind erosion mainly occurred in spring and autumn were the important factors for the fragmentation of the horse dung pats.

Key words: Grazing, Leymus chinensis, Phragmites communis, Leaf tissue turnover, Comparison