| Soil organic carbon in farmland is susceptible to strong human disturbance and can be adjusted in a relatively short time, it have "source" and "sink" intensities functions of atmospeheric CO2, and the study of carbon balance is significant to implement the policy of "Fixing Carbon and Reducing Discharge" and "Paris Agreement". Upland covers more than 70% of China’s cropland, it is an important part in fixing atmospheric CO2. This study linked the biogeochemical DNDC (DeNitrification and DeComposition) model to a newly soil map with improved spatial high-resolution (1:50000 soil database) of the northern Jiangsu Province. Taking the upland in the 29 counties (or cities) of the northern Jiangsu Province, a part of Huang-Huai-Hai region North China Plain as research area. Our objective is to model specified and common variety of climate change scenatios in IPCC report from 2010 to 2039, and analyze the variations of upland soil organic carbon with the change of future climate. The results shows Huang-Huai-Hai region North China Plain upland respond to future climate change, at the same time it make reasonable carbon fixing and reducing discharge measures to provide theoretical basis. The main results are as follows:l.The normal processing scenario simulation results from 2010 to 2039 shows, if upland in northern Jiangsu Province keep the current agricultural management and meteorological data for nearly 30 years,there would be a strong "carbon sink" effects in the future. The carbon sequestration amount is 41.76 Tg, with the average annual SOC increase of 50-780 kg C hm-2, the average annual carbon sequestration rate is 355 kg C hm-2 y’.The order of the average annual SOC changes in various types of soil in the next 30 years is: Fluvo-aquic soil (372 kg C hm-2 y-1)> Purplish soil (367 kg C hm-2 y-1)>Saline soil (345 kg C hm-2 y-1)> Cinnamon soil (344 kg C hm-2 y-1)> Lime concretion black soil (333 kg C hm-2 y-)> Brown soil (324 kg C hm-2 y-1)> Lithosol(210 kg C hm-2 y-1)> Limestone soil (175 kg C hm-2 y-1). Among them, the initial SOC content in Lithosol and Limestone soil on average annual carbon sequestration rate has maximum effect, can explain 84.1%-97.9%of the mean dSOC; the average annual carbon sequestration rate of Saline soil and Fluvo-aquic soil has greater impact because of the clay content, can explain 30.9%-47.3% of the mean dSOC; the high average annual carbon sequestration rate occurs in Brown soil and Purplish soil may with larger nitrogen fertilizer and organic fertilizer application amount; Cinnamon soil and Line concretion black soil with high average annual carbon sequestration rate mainly related to high clay content and low initial SOC content.2.The simulation results obtained from 2010-2039 in ten climate scenarios about the temperature, rainfall, atmospheric CO2 concentrations and nitrogen deposition concentration, with the average annual carbon sequestration rate as fllow:atmospheric nitrogen deposition concentration increased 2 times (373 kg C hm-2 y-1)> atmospheric nitrogen deposition concentration increased 1 times (365 kg C hm-2 y-1)> atmospheric CO2 concentration increased 2 times (364 kg C hm-2 y-1)> atmospheric CO2 concentration increased 1 times (360 kg C hm-2 y-1)> rainfall decreased 20%(359 kg C hm-2 y-1)> atmospheric CO2 concentration increased 0.5 times (357 kg C hm-2 y-1)> normal processing (355 kg C hm-2 y-1)> atmospheric nitrogen deposition concentration decreased by 0.5 times (348 kg C hm-2 y-1)> rainfall increased 20%(345 kg C hm-2 y-1)> temperature rises 2 ℃ (326 kg C hm-2 y-1)> temperature rises 4 ℃ (291 kg C hm-2 y-1). In general, upland in northern Jiangsu Province under different climate change scenarios predict a "carbon sink" effect in the next 30 year, but compared with the normal processing, with nitrogen deposition concentration decreased 0.5 times, rainfall increased 20%, temperature rises 2 ℃ and 4 ℃ the average annual carbon sequestration rate of the atmospheric were decreased.3. The simulation results shows, the carbon sequestration amount in 4 scenarios including T1P1 (temperature rises 2 ℃ and rainfall decreased 20%), T1P2 (temperature rises 2 ℃ and rainfall increased 20%), T2P1 (temperature rises 4 ℃and rainfall decreased 20%) and T2P2 (temperature rises 4 ℃ and rainfall increased 20%) are 39.10 Tg C,37.39 Tg C,34.69 Tg C and 33.64 Tag C respectively. And the average annual increase of organic carbon changes were in the range between 74-649 kg C hm-2 y-1,63-643 kg C hm-2 y-1, 92-536 kg C hm-2 y-1 and 84-518 kg C hm-2 y-1, the average annual carbon sequestration rate is 332 kg C hm-2 y-1,318 kg C hm-2 y-1,295 kg C hm-2 y1 and 286 kg C hm-2 y1 respectively. In general, upland in northern Jiangsu Province under 4 temperature and rainfall change scenarios shows "carbon sink" effect in the next 30 years, however the average annual carbon sequestration rate is decreased, and the T2P2 scenario have lowest accumulation rate.4. According to different climate scenarios from upland average annual carbon sequestration rate analysis of factors affecting in northern Jiangsu Province from 2010 to 2039 shows that, the initial SOC content and clay content are the sensitive factors to the upland average annual carbon sequestration. Pearson’s test showed that the average annual carbon sequestration rate had significant negative correlation with initial SOC content (p< 0.01), the correlation coefficient varied from-0.478 ～-0.562; while the average annual carbon sequestration rate had significant positive correlation with clay content (p< 0.01), the correlation coefficient varied from 0.199-0.325. Further multiple linear step wise regression analysis showed that initial SOC content and clay content has high variation in the average annual carbon sequestration rate were 27.6%-39.2% and 22.8%-31.5% respectively, while bulk density and pH had a lesser effects to the average annual carbon sequestration rate. Therefore, it is necessary to ensure the accuracy of the simulation results in order to improve the accuracy of the simulation results in the organic carbon simulation in the future. |
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