Simulation Of Soil Organic Carbon Dynamics In Desert Steppe Based On Century Model

This study was based on the Stipa breviflora desert steppe ecosystem and used a continuous 14-year control grazing experimental plot(0,0.91,1.82,and 2.71 sheep/hm~2/year)as a research platform.Using the soil and meteorological data within the test plot and combining relevant parameters to localize the parameters of the Century model,simulate the changes in the aboveground stand crop,and then verify with the measured data.Using the validated model to simulate the trends of soil organic carbon pool and its component pools in the experimental plots from 2004 to 2017.Study its relationship with climatic factors,and simulate analysis the response process of soil organic carbon pool and its component library for different stocking rates.The main results are as follows:(1)The simulation results after the localization of the Century model can better reflect the annual and interannual dynamic changes of the aboveground stand crop of different stocking rate plots in the desert steppe.With the increase of the stocking rate,aboveground stand crop was significantly decreased.The simulated values of the model fit well with the measured values in the study area.Except for heavy grazing plots,the determination coefficient R~2 in other plots ranges from 0.7624 to 0.8296.The Century model has good applicability in the desert steppe ecosystem.(2)During the experiment period,the soil organic carbon in the desert steppe was slowly accumulating.The soil organic carbon storage increased from 1877 g/m2 in 2004 to2073 g/m~2 in 2017.In the soil organic carbon fraction pools,active soil organic carbon and slow soil organic carbon have a positive correlation with the increase of soil total organic carbon,but passive soil organic carbon and total soil organic carbon show extremely significant negative correlation.(3)Analysis of the correlation between soil organic carbon pools and their fraction pools and climatic factors(temperature and rainfall)revealed that,in addition to the negative correlations between passive soil organic carbon and precipitation,precipitation has a significant role in promoting soil organic carbon and other two component pools.The effects of temperature on soil organic carbon pools and their fraction pools did not reach significant levels.(4)During the 14-year model simulation,the soil organic carbon density in the control plots and the light grazing plots showed an upward trend.From 2004 to 2017,the soil organic carbon density increased by 10.4%and 9.8%,respectively.There was no significant change in the moderate grazing plot;the soil organic carbon density in the heavy grazing plot decreased by 10%compared with the initial period of grazing.