Effects of Afforestation on Soil Bulk Density and pH in the Loess Plateau, China

Sustainable land management requires a clear understanding of the changes in soil quality. In exploring whether afforestation has the potential to improve the soil quality in China's Loess Plateau, soil bulk density (s) and pH were compared under five treatments: three forested treatments (16-and 40-year-old apricot stands, and 40-year-old poplar stands), and individual abandoned and cultivated treatments, serving as the controls. Bulk density across the 0-1.0 m soil profile under the 16-year-old apricot treatment (1.12 Mg m(-3)) and 40-year-old poplar treatment (1.16 Mg m(-3)) were significantly smaller than their counterparts under the cultivated (1.20 Mg m(-3)) and abandoned treatments (1.23 Mg m(-3)). Soil pH of the cultivated treatment (8.46) was significantly lower than that of the abandoned treatment (8.51) or than that of any forested treatment. The s and pH were both affected by stand age, with the s and pH of the 40-year-old apricot treatment being 0.10 Mg m(-3) and 0.05 units greater, respectively, than those of the 16-year-old apricot treatment. Treatment and soil depth appeared to interact to influence the s, but this same interaction did not influence the soil pH. This study suggested that afforestation species and stand age should be taken into consideration to harvest maximum benefits from the afforestation efforts.