Study On The Impact Of 1998 Flood On The Landscape Pattern Of Saline-alkali Soil In Zhenlai County Jilin Province

Soil salinization has become an international issue that relates to problems of resource, ecological environment and the sustainable development of agriculture. It is very important to understand and master the effect of flood on saline-alkali soil spatial pattern change, because most of saline-alkali soil distribute in flooded area. This thesis took Zhenlai county for study area. Supported by RS and GIS, and combining Landscape theory, the effect of flood on soil salinization was analyzed. Methods and results of the study are as follows:(1) Based on TM or ETM data in 1996 and 2000, the information about land types especially saline-alkali land of Zhenlai county was obtained. It indicates that the area of saline-alkali land is 1550559hm2 in Zhenlai county. The low-grade saline-alkali soil is 76269hm2, the middle-grade saline-alkali soil is 58327hm2, and heavy saline- alkali soil is 18063hm2, The area of saline-alkali soil of Zhenlai county increased in evidence, the increased area of all saline-alkali soil is 48511hm2,including 26668hm2 bow-grade saline-alkali soil. But heavy saline-alkali soil had reduced 6988hm2.(2)To study the relationship between flood and soil salinization, the flooded information of Zhenlai in 1998 was gained from the SAR data in 1998. By the way of spatial analysis, the flood area and saline-alkali area were overlayed in the same coordinate system. Results show that the flood submerged most soil salinization area , about 63.5% of soil salinization area in 1996 was submerged.(3) Comparing the spatial distribution change of saline-alkali land in flooded area and non-flooded area, it can be found that saline-alkali soil acreage was increasing, but the extent was different. And it is less in flood area than in non-flood area. The increased area of low-grade saline-alkali soil is less in flood area than in non-flood area. Middle-grade saline-alkali soil area decreased and changed to heavy saline-alkali soil, so heavy saline-alkali soil area increased. And the decreased area is more in flood area than in non-flood area. Consequently, flood aggravates soil salinization in Zhenlai county.(4) Soil salinization is the result of multi factors. There are relationship and effect between each both of these factors. Only if alter one of these factors, the formative conditions of soil salinization would be changed and form different saline-alkali land type. So it can be concluded that flood is the main cause for soil salization change, but not the only one cause.(5) Flood have two contrary effect on soil salization, one is to reduce soil salization, the other is to increase soil salization. But when discussing the effect of the flood on soil salization in Zhenlai county, it can be found that the flood mainly increasing the soil salization.