Phosphorus Accumulation in Soils Along an Urban–Rural Land Use Gradient in Hangzhou, Southeast China

Abstract

The transformation of landscapes from nonurban to urban land use has potential to greatly modify soil phosphorus (P) pools. There is minimal information on variation of P pools along urbanization gradients. Soils in five zones along an urban-rural land use gradient in Hangzhou city, southeast China, were analyzed for total P, Olsen-P and P fractions. Along the urban–rural land use gradient, soil P concentration and storages varied significantly. The urban and suburban areas had significantly higher soil P than the rural area. The results suggest that physical disturbances and inputs of various materials by humans can alter P pools in the soils. The urban and suburban soils were enriched with P varying from 1.1 to 12.0 times for total P (TP) and 1.6–32.9 times for Olsen-P as compared with the rural soils. The relative abundance of the various P fractions in the urban and suburban soils decreased in the order of HCl-P > organic P > residual P > NaOH-IP > NaHCO3-IP > H2O-P. The HCl-P was the dominant fraction and accounted for 42.3–81.0% of TP. Compared with the rural soils, the old urban and new suburban vegetable soils had a higher TP/C ratio, and the new urban and old suburban vegetable soils had a lower TP/C ratio. In old urban zone, the maximum P soil layer appeared as buried under different depth whereas in other soils as surface.