Abstract: Salinity status and salinization of the surface soil are the ultimately reflections of accumulation and migration of surface soil salinity under the dry season climatic conditions. They are the results of the combined effects of many factors. Thus, how to quantitatively evaluate each factor is very important to recognize the soil salinity cumulative process. In this paper, the surface(0-5 cm)soils of semi-arid North China Plain Saline area were studied. Internal and external influencing factors such as sources of salt, salt content of subsoil 5-10 cm and intermediate soil 20-30 cm(Sal_5-10 and Sal_20-30), salt chemical compositions, such as total alkalinity(TA), sodium adsorption ratio(SAR), soluble sodium percentage(SSP), sodium dianion ratio(SDR), and chlorine sulfur ratio (Cl^-/SO₄^2-), groundwater conditions, such as groundwater level(GWL), pH, and total dissolved solids(TDS), regional climate, such as temperature(T), and terrain conditions, as topography height(H)were considered comprehensively. Path analysis method was used to evaluate the intensity of each influencing factor. Results showed that the absolute values of the factors'direct path coefficient were in the range of 0.03 to 1.30, the descending order was Sal_5-10 >Sal_20-30 >SAR >TDS >SSP >GWL >pH >SDR >T >TA >Cl^-/SO₄^2- >H. From the indirect path coefficients, the indirect path coefficients of heart soil Sal_20-30 accumulate salts to the surface soil by the subsoil Sal_5-10 was 1.25, while the indirect path coefficients of subsoil through the heart soil was -0.93. The chemical compositions of soil salinity such as SAR, SSP, SDR, and Cl^-/SO₄^2-, which became larger after cumulative effect of salt on the surface by the sub-soil salinity effect, were followed by the former factors. Taking all the factors affecting the interaction and from the sum of the path coefficients, the strength order of the cumulative impact on surface soil salinity was Sal_5-10 >Sal_20-30 >TDS >SAR >SSP >TA >pH >Cl^-/SO₄^2- >SDR >T >GWL >H. Therefore, each factor influenced on the surface soil salt accumulation process through direct and indirect effects. Overall, the maximum impact factor was the sources of salt, and then the salt composition and groundwater conditions; regional climate and terrain conditions were the least impact factors. For the single factor, Sal_5-10 which reflected the sources of slat, SAR which reflected the soil chemical compositions, and TDS which reflected the groundwater conditions were the main controlling factors. These results will provide scientific references on the study of soil salinization process and the impact of its mechanism of the semi-arid North China Plain.

Key words: Semi-arid plain, salt accumulation, influence factors, path analysis