The Study Of Soil Organic Carbon Cycling Response To Land Salinization

The western of Jilin Province is the important agricultural region in Northeast Plain,and is one of the most development potential areas of agriculture,that is the transition zone between agriculture and animal husbandry in Northern China;furthermore,it is more important of farming-pastoral transitional zone in the Northern China,over the past decades.Due to natural factors(warm-wet climate trend in Northern China)and human activities(mainly refers to agricultural production,wetland reclamation,etc.),the significant decline of soil organic carbon content,which improves the soil fertility,seriously affected the sustainable development of regional agriculture and the protection of the wetland ecosystem,and endanger the country's food security and the protection of natural resources,so that the land salinization problems became the main resistance for developing economy in the study area.The land degradation in western Jilin(desertification,salinization and water erosion)is the main ecological environment problems in the study area.The land degradation has become the serious impacted factor of the regional economic development;however,the study of the soil organic carbon responsed to land salinization in western Jilin is still seldom reported,based on 3S technology.To promote the 3S technology application in the national land resource survey,the western of Jilin was selected as the main research area,and then,according to the actual field investigation situation and the distribution of the sampled points,the Da'an is taken as the key observation area.Combined with the geostatistic and traditional statistical method,the research method is mainly used to statistical analyze the spatial variations feature of soil organic carbon in western Jilin,provided the scientific basis for the change mechanism of the regional soil organic carbon reservesand the research of terrestrial ecosystem carbon cycle in semi-arid zone.The main research results are as follows:(1)Determine the main salinization land feature in western JilinThe collecting samples with the moderate alkaline level come form the key observation district,is salinzed soil,accounting for 89.50%(p H > 8.50,EC <4.00ds/m and SAR > 13)in the study area,2016.the strongly alkalized and lightly salinized land is one of the main forms of Da'an soil salinization area;moreover,the strong alkalinity and light acidity salt concentration in the topsoil is more consistent with the characteristics of the alkalized soil in the study area.The correlation both p H and Na+ show significant positive value,and passed the test of significance(0.84,p<0.01),In a word,the soil salinization degree in western Jilin results from the influence of strong alkali and weak acidic salts.(2)Spatial variation characteristics of the salinization land in western JilinThe spatial variation feature of land salinization in western Jilin has entered into a new period.The soil salinization degree has increased in western Jilin,and the moderately alkalized soil converted into the strongly alkalized soil,that is a major change form in the study area.The strong alkaline degree of salinzed soil is mainly occurred in the steppe chernozem.However,both the meadow soil and the composite soil were the main development soils of the moderately alkalized and lightly salinized soil.The strongly alkalized and lightly salinized land focuses in the south-east part of Huolin River in the region,2005-2016.The land types converted into the moderately alkalized and lightly salinized land in the study area is dry field of which is 162.40km2 in the area,accounting for 23.67% of the total degradation area,that is the mainly saline-alkali form after reclamation of cultivated land,2009-2016.In recently years,the cultivated land salinization has become the main source of the salinization land in western Jilin.A series of ecological problems caused by the cultivated land salinization is must be resolved,such as the land degradation and secondary salinization in the irrigation area.(3)The spatial pattern of soil organic carbon in the saline areaThe soil organic carbon density gradually reduces from the northeastern to the southwestern in western Jilin,2016.The correlation both the spatial distribution of soil organic carbon density and the vegetation cover types in the study area pass through the test of significance difference of groups.The soil organic carbon density of the grassland is highest(3.02kg/m2),the grassland has act as a stable role of soil organic matter,improved soil structure.The land use/cover types are the main control factor of the soil organic carbon density in western of Jilin.Storage of the soil organic carbon decreased significantly from 1024.3412×104 t to 629.8499×104 t,with a net decrease range of 394.4913×104 t.(4)The temporal variation of soil organic carbon in salinzed soil area,JilinThe study area is divided into two regions based on the temporal variations of the soil organic carbon density: 1)the soil organic carbon increased region,including L.chinensis grassland in Jiangjiadian(Increase value,3.74kg/m2)and the rump wetland in southern Yueliang Lake(Increase value,4.66kg/m2);2)the soil organic carbon decreased region,including the moderate salinity area in northern of central study area(decrease value,-4.83kg/m2)and the more stronger salinity area in southern of central study area(decrease value,-3.30kg/m2).(5)the changed analysis of the soil organic carbon densityA regression model to fitting the soil organic carbon density through these ecological factors,including the vegetation information,the climate information,the water information,the land use information and the terrain information,was established with the method of quadratic orthogonal rotary regression.In saline area,the correlation both the change of soil organic carbon density and the cumulative scale of NDVI in the growing season showed significant(0.36,p<0.01).In normal area,both the soil moisture is the main impact factors in the dynamic changes of the soil organic carbon density(0.54,and p<0.01).