In order to explore the temporal and spatial variations of soil salinity under human cultivation and natural conditions in the Yellow River Delta

to realize the efficient development of the reserve land resources and ensure the ecological and environmental safety

in this study

spatial transformation was used to deduce the time succession. A sampling zone was set from Lijin County Beisong town to the Yellow River Estuary in a protected area（118°10′50″E to 119°09′02″E，37°26′37″N to 37°49′36″N）along the Yellow River to reveal the temporal and spatial characteristics of soil salinity in the farmland of typical crops (wheat

cotton

rice) and under natural conditions. 28 main sampling areas were randomly selected and 140 samples were collected

with every 20 cm as a soil layer

and the salt content of 0—100 cm soil layer was determined. in samples. The results showed that the average soil salinity in 0—20 cm soil layer was 3.58 g/kg in the sampling belt

which was significantly (P＜0.05) higher than that in the 60—100 cm and soil layer

and these soils were of moderate salinity. The salinity distribution showed a strong spatial variability（CV=131%） in the 0—60 cm soil layer

but with the increase of soil depth

the coefficient of variation decreased continuously. The spatial distribution characteristics of soil salinity profile reflected the temporal effect of cultivation and natural conditions. Inverted salinity profiles were mainly distributed in the coastal zone

which accounted for 83.3% of the alluvial area formed after the year of 1972

and the main vegetation types were low-yield cotton crops and natural vegetation

which accounted for 45.5% and 85.7%

respectively. The average salinity profiles were mainly distributed in the middle and inland regions of the sampling area

which both accounted for 40.0% in regions formed before 1855 and during 1855 to 1972

respectively

and the main vegetation types were rice

wheat and intertidal zone. The normal salinity profile types were mainly distributed in the inland regions of sampling zone (which accounted for 31.3% of the area formed before 1855)

and the main vegetation types were farming field

with cotton

wheat

and rice fields being distributed equally. Random factors such as

cultivation management and vegetation were the main factors that caused the variation in soil salinity in 0—80 cm soil layer

with the increase of soil depth

the effects of these random factors weakened

but the effects of structural factors such as drainage and groundwater level became stronger. Based on the spatial evolution characteristics of soil salinity

a map of crop distribution was made to provide a support for the development and utilization of saline soil in the Yellow River Delta. In conclusion

the study revealed the time-spatial revolution characteristics of soil salinity in the Yellow River Delta under different land cultivation and natural conditions

i.e. from coastal to inland

the soil salinity profile changed from inverted salinity profile to normal salinity profile. Cultivation can reduce soil salinization so some degree

but cultivation and soil salinization are reciprocal causations and can promote the development of each other.