Spatial Distribution Characteristics For Soil Salinity And Nutrients At The Estuary Of Huai River

Spatial structure of soil characteristics is the result of the interaction of variety of factors(biology, chemistry and physics). Learning the spatial distribution of soil characteristics is important for establishing the reasonable management mode, and the premise of sustainable use of soil resources. The land use types and ecological environment of Huai River Estuary exist large spatial heterogeneity. Based on the soil heterogeneity, it is significant for the status of ecological construction of water and soil conservation and and improvement of national land.Taking the estuary of Huai River as study area, the spatial distribution characteristics of soil nutrient indexes, i.e., soil organic matter(SOM), available nitrogen(AN) and available phosphorus(AP), for various depth layers(0 ~10 cm, 10 ~20 cm, 20 ~50 cm and 50 ~100 cm)and salinity, pH for various depth layers(0 ~10 cm, 10 ~20 cm, 20 ~50 cm, 50 ~100 cm, 100 ~150 cm, 150 ~200 cm, 200 ~250 cm and 50~300 cm) and related affecting factors were analyzed by using mathematical statistics and geostatistics methods. The study contents mainly included: spatial variability of soil salinity, pH and nutrients; the salinity profile types based on systematic cluster analysis; the analyses of influencing factors.The main research conclusions are as follows:(1) The coefficient of variation for soil salinity in each layer belonged to moderate degree, and soil salinity in each layer was moderate spatial dependence. The spatial variation of surface soil salinity affected by random factors, and that of subsurface soil mainly affected by structural factors. With the increasing depth of soil layer, the influence of structural factors presented a increasing trend, while the random factors presented a downward trend. Salinity presented a downward trend with the increasing distance from the estuary, and the soil salinity distribution trend of all layers were similar. The salinity at the estuary of Huai River were mostly classified as moderate salinization, mild salinization and desalinization. The saline and severe salinization soils were mainly distributed in the 0~20 cm soil layers, within 800 m from the estuary. The critical desalinization positions of the floodplain, and dike outer were respectively located at 2400 m and 1800 m from the estuary(2) The salinity profile types were obviously classified into the types of surface accumulative, balanced and bottom accumulative, respectively accounted for 29%, 18%, 53% of the total number of profile. The distributions were concentrated and respectively located in the severe salinization zone, moderate salinization zone, mild salinization and desalinization zone. The three salinity profile types could transmute into each other.(3) The coefficient of variation for soil pH in each layer belonged to low degree of variability. Soil pH in 0~20 cm layers were moderately spatial dependence,and soil pH in 20~300 cm layers were strong spatial dependence. Soil pH were between 7.5~9.5, and a small amount weie strong alkaline soil, respectively located at 1000 m from the estuary(0~300 cm layers)(4) The coefficient of variation for SOM and AN in 0~20 cm layers belonged to moderate degree, and that in 20~100 cm layers belonged to low degree. The coefficient of variation for AP in each layer belonged to moderate degree. Soil SOM, AN and AP in 0~20 cm layers were moderately spatial dependence, and that in 20~100 cm layers were strong spatial dependence. SOM and AN content presented an increasing trend with the increasing distance from the estuary. The SOM and AN content in 0~20 cm layers respectively belonged to moderate and rich level, and both of that in 20~300 cm layers belonged to low level. The AP content in 0~20 cm layers mostly belonged to moderate, rich, and extremely rich level. The AP content in 20~100 cm layers mostly belonged to low level.(5) The spatial distribution pattern of soil nutrient and salinity was closed related to soil parental material, soil texture, distance to sea, land use pattern and management measure.