Variation Of Soil Greenhouse Gas Fluxes And The Influencing Factors In The Environment In Horqin Dune-meadow Cascade Ecosystem

This paper is based on the cascade-distributed semi-mobile dunes,fixed dunes,artificial forestlands,farmlands and meadow wetlands in the Horqin dune-meadow cascade ecosystem.The author measured the soil greenhouse gas fluxes in the growing season using static chamber/gas chromatograph technique,compared and analyzed the diurnal,seasonal and interannual variations of soil greenhouse gas fluxes in the region,and explored the change of soil greenhouse gas fluxes and the respective response to the influencing factors with the soil environmental data measured in the hydrometeorological station and in the field.The main findings are as follows:(1)The diurnal variations of semi-mobile dunes and meadow wetlands during the growing season were significantly different(P<0.05),and the trend of diurnal greenhouse gas fluxes was mainly dominated by soil temperature.(2)The greenhouse gas fluxes of semi-mobile dunes,fixed dunes,artificial forestlands,farmlands and meadow wetlands in the Horqin dune-meadow cascade ecosystem were significantly different(P<0.05),and the seasonal changes were obvious.Soil temperature and soil moisture had significant effects on soil greenhouse gas fluxes during the growing season(P<0.05).(3)The average CO2 flux of the Horqin dune-meadow cascade ecosystem in 2017 showed:semi-mobile dunes(180.85 mg·m-2·h-1)<fixed dunes(241.31 mg·m-2·h-1)<artificial forestlands(357.14 mg·m-2·h-1)<farmlands(404.54 mg·m-2·h-1)<meadow wetlands(486.16 mg·m-2·h-1);The average CO2 flux in the growing season in 2018 showed:semi-mobile dunes(236.61 mg·m-2·h-1)<fixed dunes(267.91 mg·m-2·h-1)<artificial forestlands(397.88 mg·m-2·h-1)<farmlands(450.68 mg·m-2·h-1)<meadow wetlands(541.49 mg·m-2·h-1).The CH4 and N2O fluxes have the same regularity as the CO2 flux.The main reason is that the total organic matter,total nitrogen and total phosphorus in cascade-distributed semi-mobile dunes,fixed dunes,artificial forestlands,farmlands and meadow wetlands exhibited the characteristic of cascade distribution.According to the analysis results,the CO2 flux was positively correlated with total organic matter and total phosphorus content,and the CH4 flux was negatively correlated with total organic matter(ie,CH4 absorption was positively correlated with total organic matter).And there is a positive correlation between N2O flux and total nitrogen content.(4)The influence of rainfall on greenhouse gas fluxes mainly refers to the changes of soil root respiration intensity and microbial activity in the soil by rapidly increasing the soil moisture in a short time,thus changing the soil greenhouse gas fluxes.(5)Litter had obvious promoting effect on soil CO2 and N2O emission,and had obvious inhibitory effect on soil CH4 absorption.The reduction of CO2 and N2O emissions in the set of litter removal was much greater than the increase of CO2 and N2O emissions in the set of double litter.The increase or decrease of soil greenhouse gas fluxes influenced by soil litter is not linear.The temperature sensitivity(Q10)of the three sets were as follows:litter removal(1.070)>the original set(1.046)>double litter(1.011).The addition of litter did not significantly affect the sensitivity of greenhouse gas fluxes to soil temperature(P>0.05).(6)The addition of biochar in the farmland effectively reduced the cumulative CO2 and N2O emissions in the growing season of corn in Horqin,and promoted the soil absorption of CH4.This paper provides a reference for the study of greenhouse gas fluxes in Horqin area,and provides scientific guidance for agriculture in desertification areas.