The Study On The Variation And Storage Of Soil Carbon Of Saline-alkaline Paddy In Qianguo County Of Jilin Province During Freezing-thawing Period

Soil carbon library is the most active carbon in terrestrial ecosystem, its dynamic change directly affects the global climate change. Soil carbon library includes soil organic carbon and inorganic carbon library, much of the global change researchachievements, however, pay attention to the dynamic change of soil organic carbon,less consider the change of the soil inorganic carbon, especially the variations of soilinorganic carbon in freezing-thawing period. In semi-arid seasonal frozen soil area,there are lots of organic carbon and inorganic carbon in soil. Through changing soilphysical, chemical properties and microbial activity, freezing-thawing cycle effect caninfluence soil ecosystem carbon cycle process, organic carbon and inorganic carbonreserves and the assessment of carbon source/carbon sink in terrestrial ecosystem.The study was supported by my tutor’s National Natural Science FoundationProject——Soil organic carbon change mechanism and warming potential researchof saline-alkali paddy soils throughout the year in JilinProvince. This paper, whichchose the saline paddy soil of Qianguo County in the west of Jilin province as theresearch object, through the combination of field sampling and plot experiment,studied the freezing-thawing characteristics of paddy soil with different types duringfreezing-thawing period, monitored the change of soil temperature, soil depth andsnow depth, studied the dynamic change rule of soil organic carbon and inorganiccarbon, analyzed the relation between soil organic carbon, inorganic carbon and soilphysicochemical properties and the relation between dynamic migration andtransformation of soil organic carbon, inorganic carbon, estimated the change oforganic carbon storage and inorganic carbon storage of0-50cm paddy soil in QianguoCounty during freezing-thawing period.The soil temperature of different paddy fields was monitored from October7,2012to May10,2013. The result showed that soil temperature change dramatically indifferent freezing-thawing period, affected by the change of air temperature and solarradiation during freezing-thawing period. The soil temperature of different paddyfields were different in the same period, because the siol type, the soil texture, theorganic matter content, clay content and other initial soil conditions of them were different, but the change trend of them were consistent. Solar radiation, airtemperature and snow cover could affect soil temperature, controling seasonalfreezing-thawing characteristics of soil.The study on soil organic carbon and inorganic carbon content changes indifferent freezing-thawing period showed that soil organic carbon changeddramatically in seasonal freezing-thawing cycle process. The variation trend oforganic carbon content of different type and different depth soil declined first and thenincreased. After freezing-thawing cycle, organic carbon conten reduced. The variationtrend of inorganic carbon content of different type and different depth soil decreasedafter increased and then increased. After freezing-thawing cycle, all kinds of surfacesoil inorganic carbon content increased. Freezing-thawing action and the deep of soilinfluence have significant effect on organic carbon and inorganic carbon.By monitoring the soil physicochemical properties in different freezing-thawingperiod, the result showed that hydrolyzed nitrogen, pH, soil moisture content, saltcontent have significant change. During freezing-thawing period, soil organic carbonand nitrogen hydrolysis, moisture content, salt content are positively correlated, butorganic carbon and pH were negatively correlated. Soil inorganic carbon and nitrogenhydrolysis, moisture content, salt content are negatively correlated, but inorganiccarbon and pH are positively correlated. There was a negative correlation betweenorganic carbon and inorganic carbon during freezing-thawing process and thecomplicated transfered and conversion between organic carbon and inorganic carbonin time and space.Based on statistical analysis of experimental test data, the study estimated thedensity of organic carbon and inorganic carbon of0-50cm paddy soil in QianguoCounty during freezing-thawing period, also estimated the organic carbon storage andinorganic carbon storage by using area weighted method. The result showed that soilorganic carbon density declined first and then increased, soil inorganic carbon densitydecreased after increased and then increased, during freezing-thawing period. Afterfreezing-thawing cycle, organic carbon storage of0-50cm paddy soil reduced, whichwas4.89×106t, while inorganic carbon storage increased, which was6.13×106t.The results could be used as the foundation of the annual soil carbon storages of the study area, making up for the deficiency of previous studies which only considersorganic carbon of the growing season. The study could provide references for themigration and transformation relation between soil organic carbon and inorganiccarbon of permafrost zone and local data support for the study of global climatechange.