华北半干旱平原区表层土壤盐分累积的影响因素分析

定量评价各因子对盐渍区表层(0~5 cm)土壤盐分累积的影响,以华北半干旱平原为研究区,综合考虑盐分来源、盐分化学组成、地下水状况、区域气候,地形条件等内外影响因素,应用通径分析方法评价各影响因子强度。结果表明:各影响因素通过直接和间接作用于表层土壤积盐过程,总体看盐源对表层土壤积盐影响强度最大,其次是盐分组成,再者是地下水状况,而区域气候和地形的影响较小。单因素而言,反映盐源的Sal_5-10、反映土壤盐分组成的SAR和反映地下水状况的TDS是主要的控制因素。研究结果为认识华北半干旱平原土壤盐渍化过程及影响机制提供参考依据。

Influencing factors on surface soil salt accumulation in the semi-arid North China Plain

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.