| The soil has both a huge amount of organic carbon and a huge potential for carbon fixation.Some slight changes in soil can also affect the changes in carbon concentration in the atmosphere.Among them,cultivated land is more susceptible to human activities.Studying the current status of soil organic carbon(SOC)and its changing characteristics can help promote the accumulation of SOC alleviate the global warming process.Huang-Huai-Hai Agricultural Area was selected as the research area,and dry land was used as the research object.Huang-Huai-Hai Agricultural Area is an important grain and oil production base in China,of which dry farmland accounts for 71.23%of the area of Huang-Huai-Hai Agricultural Area.Dry farmland is the most important type of land use in Huang-Huai-Hai Agricultural Area.Studying the status and change characteristics of SOC in the dry farmland of Huang-Huai-Hai Agricultural Area can provide effective reference materials for soil management and land use decisions in the study area.Based on the land use map of 1:1 million and the soil database of 1:1 million,the dry farmland soil map of Huang-Huai-Hai Agricultural Area was obtained.The dry farmland soil polygons was used as the basic unit for simulation.Collect the meteorological,agricultural management,crop growth and other data of Huang-Huai-Hai Agricultural Area,as well as the data required for point simulation and regional simulation.Initialize the parameters of the model to prepare for the simulation.Point simulations and regional simulations were performed.After the simulation results were qualified,the dynamic of dry farmland SOC in Huang-Huai-Hai Agricultural Area from 1985 to 2015 was simulated based on the CENTURY model.The study reached the following conclusions:(1)The point verification of the model is obtained.The simulation efficiency ME of the four point verification is in the range of 0.25 to 0.39,the relative error E?± 10%,and the linear fitting R2 is in the range of 0.610 to 0.728.The measured data from the four points of Mengcheng,Xingtai,Huojia,and Jinan fit well with the model simulation data.The correlation coefficient r of the regional verification is 0.29,and the results of the regional verification are acceptable.It can be seen that the CENTURY model is suitable for fitting the study area.(2)The overall dry farmland SOC in Huang-Huai-Hai Agricultural Area showed an upward trend.The specific manifestation is that the dry farmland soil organic carbon storage(SOCS)in Huang-Huai-Hai Agricultural Area in 2015 was 956.27 Tg,which was an increase of 106.04 Tg compared to 1985,and the growth rate was 3.42 Tg a-1.The soil organic carbon density(SOCD)in Huang-Huai-Hai Agricultural Area increased from 27.40 Mg C hm-2 in 1985 to 30.81 Mg C hm-2,with a growth rate of 0.11 Mg C hm-2 a-1.(3)The spatial distribution of SOCD in Huang-Huai-Hai Agricultural Area is as follows:The SOCD in the Foothill Plain Agricultural Area of the Taihang Mountain in the Yanshan and the Huanghuai Plain Agriculture Area are higher than that in the Shandong Hilly Agriculture Area.The spatial distribution of SOC change is mainly manifested as follows:Soil with ? SOCD>10 Mg C hm-2 are mainly distributed in the Agricultural Area of the Low-lying Plain of Hebei Shandong and Henan.The soil with ? SOCD in the range of 0-5 Mg C hm-2 are mainly distributed in the Shandong Hilly Agriculture Area and the Agricultural Area of Huanghuai Plain.The soil with ?SOCD in the range of 5-10 Mg C hm-2 is mainly distributed in the Agricultural Area of the Foothill of the Taihang Mountain in Yanshan.Soil with decreased SOCD were scattered sporadically in Huang-Huai-Hai Agricultural Area,but mainly concentrated in the eastern area of the Foothill Plain Agricultural Area of the Taihang Mountain in the Yanshan.(4)The dry farmland soil in Huang-Huai-Hai Agricultural Area can be divided into 20 types according to soil types,including fluvo-aquic soil,cinnamon soil,skeletal soil,brown soil,shajiang black soil,alluvial soil,and cultivated loessal soil,which together occupy Huang-Huai-Hai About 99%of the dry farmland soil area in the Agricultural Area,and the remaining soil accounts for less than 1%,By studying the evolution of the organic carbon storage and density of the seven major soil types,the SOCD in 2015 is ranked in order of:fluvo-aquic soil>cinnamon soil>cultivated loessal soil>alluvial soil>Shajiang black soil>skeletol soil>brown soil.The organic carbon density of the seven major soil types showed an upward trend.The growth rate of cultivated loessal soil was the largest,increasing from 24.23 Mg C hm-2 in 1985 to 30.42 Mg C hm-2 with a growth rate of 0.20 Mg C hm-2a-1.Because the SOCD of fluvo-aquic soil is the largest and it accounts for 55.17%of the dry farmland area,it can be known that fluvo-aquic soil plays a major role in the SOCS in Huang-Huai-Hai Agricultural Area.(5)Within Huang-Huai-Hai Agricultural Area,the variability of SOCD is moderate,regardless of whether it is a large region,province,city or county.The SOCD variation coefficients of large regions,provinces,cities and counties are ranked as follows:region>province>city>county.Compared to 1985,the coefficient of variation on all scales in 2015 showed a decreasing trend.(6)Among the four factors of slope,annual precipitation,soil pH,and soil bulk density,the SOC in Huang-Huai-Hai Agricultural Area has the highest correlation with the precipitation in the same year,with a correlation coefficient of-0.479,which shows a moderate intensity negative correlation.Figure 20 table 9 reference 187... |
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