Study On The Distribution And Spatial Change Of Saline Alkali Land In Songnen Plain

Saline alkali land refers to the land where salt and alkali gather on the surface and grow natural salt tolerant plants.It is a general term of saline soil and alkaline soil as well as all kinds of salinized and alkaline soil,which is composed of one or several kinds of saline soil.Soil salinization is a major cause of land degradation in arid and semi-arid areas,which will cause soil hardening and crop yield decline.Songnen Plain,located in the middle of Northeast China,is an important food producing area in China,and also one of the three soda saline alkali soil concentrated distribution areas in the world.It is one of the areas with the most serious salinization and the greatest impact on agriculture in China.Songnen Plain is surrounded by mountains on three sides and mountains on one side.The specific landform and hydrological process of the high and middle level around,the soil forming parent material containing sodium salt and the lake facies sedimentary geological history connected with the sea,the semi-arid or semi humid climate determine that there are saline soil and the saline alkali land formed in Songnen Plain,and it is a naturally formed primary saline alkali land.Soil salinization is one of the main causes of land degradation in Songnen Plain.Soil salinization will lead to soil hardening,crop yield decline,and increase soil erosion.Therefore,in order to fully understand the saline alkali land in Songnen Plain,to study the distribution and spatial gradient change of saline alkali land determined by the geomorphic system of Songnen Plain,it is of great significance to put forward reasonable development and improvement countermeasures and control approaches.In this paper,DEM data,distribution data of saline alkali land in Songnen Plain,field data of saline alkali index of soil samples collected in different parts of different altitudes and microtopography in different catchment areas are used as data sources.Watershed of each catchment area is extracted by hydrological analysis tools,and landform classification and spatial change of saline alkali in different scales in Songnen Plain are obtained In addition,the paper puts forward the macro improvement countermeasures of micro topography transformation and surface water dredging,as well as the treatment approaches of each catchment area.Main research results \ main conclusions:(1)First,the first-class geomorphic unit of Songnen Plain is determined.There are five first-class geomorphic types in Songnen Plain,which are: low-altitude plain,low-altitude platform,low-altitude hill,low-altitude mountain and medium altitude mountain,among which the low-altitude plain is the most widely distributed.In the low altitude plain in the west of Songnen Plain,according to the river and watershed,it can be further divided into: low plain catchment in the east of Nenjiang River,Yuanqiu depression catchment in Zhongping of Taoer Hebei Province,quasi plain catchment in Huolinhe Taoerhe River Basin,ridge Tuodian catchment in the north of Songliao watershed,inclined plain catchment in Songhuajiang second Songhuajiang Lalin River Basin.In each catchment area,microtopography is further identified: Geological mound platform,geological low-lying land,wind eroded low flat land,aeolian high flat land,disturbed low flat land and residual high platform land.(2)Compared with the soil salinity indexes of 0-5cm soil layer,5-10 cm soil layer,10-20 cm soil layer,20-30 cm soil layer and 30-50 cm soil layer,the soil salinity indexes of 30-50 cm soil layer are relatively strongest,and the soil salinity indexes of 0-5cm soil layer,5-10 cm soil layer,10-20 cm soil layer,20-30 cm soil layer and 30-50 cm soil layer are relatively stronger The salinity index of cm soil layer is the weakest.(3)In different parts of microtopography,with the elevation of soil surface,the soil salinity of bare alkali spot is generally stronger than that of surrounding soil growing by community,and the soil p H,EC and ESP gradually decrease from 0-5cm soil layer to 30-50 cm soil layer,and the surface soil salinity is the strongest,while the soil salinity of each soil layer of growing Leymus chinensis community,Huwei grass community,corn and other crops community is stronger The sex is opposite to naked alkali spot.(4)In Songnen Plain,the composition of soil salt in each catchment area is relatively complex,which shows that Na + and Ca2 + are the main cations,HCO3-is the main anion,and SO42-is the second.The changes of ion composition and salt content in Songnen Plain showed that the content of Na +,SO4-and HCO3-increased with the increase of soil salt content,of which SO42-changed the most.There is a significant positive correlation between salt content and electrical conductivity,and soil salt content has an important effect on electrical conductivity;there is also a significant positive correlation between salt content and alkalinity,and soil alkalinity increases with the increase of soil salt content.(5)The suggestions of dredging and improvement are put forward for each catchment area of Songnen Plain.Since the saline alkali land in each area has an independent surface water system,it is necessary to have independent measures to transform and determine the micro landform of surface water.Generally,it is to dredge the internal flow river and Wuwei River to flow into Nenjiang river or accumulate in a fixed section to form a reservoir.