Abstract: In order to approach the microbial metabolic activity and functional diversity in black soil before and after reclamation, the cropland, grassland, and bare land with 21 years utilization or unreclaimed in the Hailun Agroecological Experimental Station were selected, and Biolog method was adopted to study the seasonal variations of the metabolic activity and functional diversity. The results showed that in spring and summer, the average well color development (AWCD) and the Shannon diversity index of soil microbes were the highest in grassland, followed by in cropland, and in bare land. In cropland and grassland, soil microbial metabolic activity and functional diversity exhibited a trend of high in summer and low in autumn; while in bare land, these two indices raised gradually with seasonal change. In the three lands, the carbon sources with higher utilization efficiency or utilization intensity by soil microbes were carbohydrates, amino acids, and carboxylic acids.

Key words: Land use change, Sediment production, Loss Plateau