Effect of different land-use patterns on the physical characteristics of the soil in the Yellow River delta region

The Yellow River delta is one of the three major pedogenic river deltas in China and is the fastest forming delta that has important reserved land resources. Anthropogenic behavior and natural development play an important role in the physical and chemical properties of the soil during pedogenic processes. In order to maintain soil fertility and ensure sustainable utilization of land resources,it is necessary to investigate the effect of various types of land uses on physical properties of the soil. In this study,disturbed and undisturbed soil samples were collected from soil covered by different vegetation. Arable soil was considered to be soil cultivated with wheat and cotton,while land covered with reeds and suaeda was considered to be natural vegetation and bare land was classified as recently formed land. These soils were considered to be trends of mature soils in the Yellow River delta region. The physical properties of undisturbed soil samples were as follows: bulk density and porosity of the soil,water-stable aggregates,and saturated moisture. The organic carbon content,available nitrogen and phosphorus content,and total salt content in the soil were probed as chemical indexes. Field research along with lab analyses was conducted at different genesis stages in order to illustrate the changing trends in soil physicalcharacteristics and to identify the causative factors. Compared with bare land soil,the soil covered with vegetation had significantly higher soil porosity,aggregate water stability,and saturated and capillary water content. Soil organic carbon content and available nitrogen and phosphorus content were higher in vegetation soil than in bare land soil. On the other hand,the total salt content and soil bulk density were significantly lower in soil with vegetation than in bare land soil. The trends in soil properties improved with different vegetation in the following order wheat cotton reed suaeda bare land.Stepwise regression and correlation analysis identified that the main factors of soil capillary water content are soil bulk density,soil aggregate mean weight diameter,and soil capillary porosity. The aggregate soil water stability was determined as 0. 25-mm water-stable aggregate content and capillary porosity. The total salt content in the soil significantly affected the soil saturated hydraulic conductivity,while 0. 25-mm water-stable aggregates had a significantly positive correlation with the soil organic carbon content( r = 0. 832