Changes Of Soil Organic Carbon In Hulunbuir Grassland Under The Policy Of Returning Grazing To Grassland

With climate change having been a more and more severe global issue in recent years,carbon sink transactions came into being.At present,carbon trading is mainly concentrated in artificial forest land,while the grassland ecosystem accounts for a small share in the market.Because of soil heterogeneity,it is difficult to accurately calculate the organic carbon reserves.This paper studies?1?The carbon layer was divided according to the main factors affecting soil organic carbon.The policy of returning grazing land to grassland was parameterized,and DAYCENT model was used to simulate soil organic carbon.?2?Using the meteorological observation data of the Hulunbuir grassland area from 1991 to 2010 as the meteorological file input by the DAYCENT model,the soil organic matter 1:1,000,000 map of Nanjing Soil Institute,the soil and vegetation measurement data of Peking University,and national vegetation data from the Institute of Botany,Chinese Academy of Sciences,the parameters of the model were adjusted and the soil organic matter content of Hulunbuir grassland from1991 to 2010 was simulated.?3?Under the climate scenario model RCPs4.5,the impact of returning grazing land to grassland policy on soil organic carbon was simulated,and the soil organic carbon of Hulunbuir grassland was calculated.?4?Soil carbon sink of Hulunbuir grassland was calculated according to grassland methodology.The main work and conclusions are as follows:1.According to the main grass species and soil type of Hulunbuir grassland,the grassland was divided into 76 carbon layers,which were simulated according to different carbon layers in the model simulation.The grass type and soil type were used as background parameters input model.2.After the parameter rate determination,the coefficient of determination of the model is 0.83-0.93,which indicates that the model can more accurately simulate the changing process of soil organic carbon in the area of returning grazing land to grassland.Comparing the observation results of meteorological stations based on Hulunbuir grassland area from 1991 to 2010 and the results of soil organic carbon simulated by RCPs4.5 scenario data,the coefficient of determination R² is 0.835,indicating that RCPs4.5 scenario data is applicable to the study on the future impacts of climate change on soil organic matter in Hulunbuir grassland area.3.Through the comparison of the changes of Hulunbuir grazing and returning grassland from 1991 to 2010,the content of soil organic matter in the grazing area increases in most areas.On the spatial distribution,the soil organic matter content in the northeastern Hulunbuir grassland and the western foothills of the Da Hinggan Ling Prefecture in the east is high,while the soil organic matter content in the western and central part of Hulunbuir grassland is low.Through the simulation of the climate situation,comparing with the continuous grazing of Hulunbuir grassland,the content of organic matter in most areas increased,and a few central areas were degraded.But the reduction was not much.4.According to the grassland methodology,the average annual carbon sink of Hulunbuir grassland will be 1,988,400 t CO₂ by 2030,and the carbon sink potential will be 51,697,300 t CO₂e.The potential of carbon sequestration in Hulunbuir grassland increases significantly,and the impact of the policy of returning grazing to grassland on soil organic matter is more obvious.