[Mn content in soil of Sanjiang Plain under different land use].

Mn content and its profile distribution characteristics were investigated in soils from the typical Deyeuxia angustifolia wetland, corn filed, paddy field, poplar forest and island forest in Sanjiang Plain. Results indicated that Mn content was relatively low and was in the range of 107.73-2 798.99 mg/kg with the average value of 403.24 mg/kg. Mn content significantly differed by land use (F = 9.272, P < 0.001) and was in the order of island forest > poplar forest > corn field > Deyeuxia angustifolia wetland > paddy field. On the whole, Mn content in each soil layer was in the order of corn filed > Deyeuxia angustifolia wetland > rice paddy in field and was in the order of island forest > poplar forest in the vertical direction. It suggested that Mn was enriched after wetlands were reclaimed in to the upland filed and Mn concentration was decreased when wetlands were changed into rice paddy. Correlation analysis showed that Mn content in soil significantly negatively related to pH (r = -0.279, P < 0.05), significantly positively related to sulfur (r = 0.383, P < 0.01) and dissolved organic carbon (r = 0.244, P < 0.05), and weakly related to soil organic matter and available sulfur, respectively. Changes of environmental factors had impacts on Mn species and then resulted in soil Mn content.