Impact of vegetation zones on soil phosphorus distribution in Northwest China

Soil phosphorus (P) fraction distribution and correlation at different soil depths along vegetation succession in wetland next to a lake in the Hongjiannao National Nature Reserve, China were studied using the Hedley fraction method. The overall trend for soil P content was calcium-bound P (Ca-P) > organic P (O-P) > aluminum/iron-bound P (Al/Fe-P) > labile-P (L-P). Ca-P and O-P were the predominant P forms in all the soil layers, representing on average 53.8-84.9% and 12.9-45.2% of the total P, respectively, whereas L-P (ranging from 0.5 to 1.5 mg/kg) was less than 1%. The soil in the Bassia dasyphylla and Carex duriuscula vegetation zones had the largest P contents. In these two vegetation zones, soil L-P was greatest in the surface soil layer; Al/Fe-P was most abundant in the deep layer; O-P was highest in the middle layer. Ca-P levels were generally similar across all soil layers. Regression analysis showed that distribution of P was highly correlated with organic carbon, total nitrogen and plant biomass. Results showed that the soils under Bassia dasyphylla and Carex duriuscula have considerable carbon input potentials, which would facilitate P mineralization as compared to other plants.