Abstract: Exploring the effects of forest types on soil organic carbon (SOC) is critical for facilitating sustainable forestry management. Here, we compared SOC contents of three forest types, including apricot forest, poplar forest, and willow forest, in Huining County in central Gansu Province, China. The results showed that, under similar site conditions, SOC contents of all the three forest types decreased with increasing soil depth. SOC content of the apricot forest ranged from 2.85 g·kg^-1 to 19.05 g·kg^-1, while for the poplar forest and willow forest, it ranged from 1.67 g·kg^-1 to 11.9 g·kg^-1, and from 1.80 g·kg^-1 to 16.05 g·kg^-1, respectively. The apricot forest had significantly higher SOC content than the poplar forest and willow forest, but lower water conservation capacity than the poplar forest. SOC content was significantly negatively correlated to soil bulk density and pH across the three forest types. Soil water content was the dominant factor affecting SOC content of the poplar forest, pH and soil water content were the dominant factors in the willow forest, while pH and soil bulk density were the dominant factors in the apricot forest. Our results suggest that during implementing afforestation in semi-arid areas, the poplar should be the preferred species if only considering the benefits of soil and water conservation. If only considering the potential of carbon sequestration, however, the apricot forest is particularly important for reducing emission and enhancing carbon sink.

Key words: Phyllostachys edulis, management measure, soil organic carbon, physical fractionation, chemical structure