The Effects Of Oxbow Lake On The Grassland Soil's Physical And Chemical Characteristics In The Gonger Drainage Area

Oxbow lake is a special lake formed on the sides of the river in plain or high-plain areas, which plays an important role in the formation of wetland and change of ecosystem through the effect on soil moisture around it. In this paper, in April to September in 2007 and 2008, on the sides of the oxbow lake of Gonger river at Keshenketeng banner of Chifeng city, in didn't form oxbow laka area, formed an oxbow laka area, formed 2 oxbow lakes area, formed 3 oxbow lakes area separately set up the sampling point,studied grassland's physical and chemical environmental factors of soil. The results were shown as follows:(1) The effect of oxbow lake on the moisture content of soil surface around it was observed. The more far soil was from the river, the more low the moisture content of soil surface was presented in the region of unformed oxbow lakes within a certain range. The moisture content of soil surface was high around the oxbow lakes, and there was a reducing trend of moisture content far away sides of river. The more oxbow lakes were formed, the more big areas the wetland was on the sides of oxbow lakes. There was a positive correlation between the moisture content of surface soil and the area of wetland around the oxbow lake. The moisture content of surface soil on the sides of oxbow lake changed largely with the seasons, but the difference decreased with an increase of distance to the oxbow lake.(2) The gravel contents of the soil in the unformed and formed oxbow lakes were higher than the contents of sand, silt and clay comparing the mechanical composition of soil at all levels; gravel content of soil from the recent site of river was low, while the contents of sand, silt and clay of which were high; the mechanical composition of soil was no apparent change with the soil depth.(3) The pH values of soil of unformed and formed oxbow lake were alkaline. The pH value increased with an increase of distance from oxbow lakes on the sides of the Gonger river.(4) The contents of soil organic matter, total nutrients (nitrogen, phosphorus and potassium) and alkaline nitrogen reduced with an increase of distance from the river; the available phosphorus content in soil decreased, then increased with an increase of distance from the river; the available potassium content in soil increased, then decreased with an increase of distance from the river; the changes of organic matter content, total nutrients (nitrogen, phosphorus and potassium) and available nutrient (alkali nitrogen and available phosphorus and potassium) in the soil of the formed oxbow lake were wave-type; which was high beside the Gonger river and the sides of oxbow lake, and showed out a decreasing trend far away from the sides of river.