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sur le développement des zones arides et semi-arides

Titre : Effect of Grazing Intensity on Greenhouse Gas Fluxes in Desert Grassland Soils

Auteur : 于志慧

Grade : Master 2022

Université : Inner Mongolia Agricultural University

Résumé
Grassland ecosystems play a very important role in regulating soil-atmosphere gas exchange,and the uptake and emission of soil carbon dioxide（CO2）and methane（CH4）in desert grassland ecosystems have an important impact on the dynamic balance of ecosystem carbon elements.As the dominant use of grasslands,grazing regulates soil greenhouse gas emissions by affecting the dynamic inputs and outputs of carbon to grassland ecosystems,and in turn provides important feedbacks to climate change.In this thesis,the characteristics of soil CO2 and CH4 greenhouse gases and their stable isotope values under three grazing intensities,control（CK）,light grazing（LG）and heavy grazing（HG）,were studied in the desert grasslands of Inner Mongolia.The dynamic changes of grassland vegetation characteristics,soil physicochemical properties,soil temperature and water content ;analyze the correlation between soil greenhouse gas fluxes and soil temperature and water content,soil physicochemical properties under different grazing intensities,and then elucidate the intrinsic mechanism of different grazing intensities affecting soil greenhouse gas emissions and uptake,the main findings are as follows.1.The height,cover,density and biomass of grassland plants tended to decrease with increasing grazing intensity,and heavy grazing significantly reduced the height and aboveground biomass of plant communities in 2021（P＜0.05）.Light grazing increased the plant community,height,cover and density,and had a tendency to increase the diversity index of the community.2.Compared with the control and light grazing,the heavy grazing treatment caused a significant decrease（P＜0.05）in soil organic carbon,total nitrogen content and carbon to nitrogen ratio,a significant increase（P＜0.05）in soil bulk weight and a decrease in soil carbon and nitrogen isotope values.With the increase of soil depth,soil capacitance and soil carbon and nitrogen isotope values increased,and soil organic carbon and total nitrogen content showed a single-peaked trend of first increasing and then decreasing.3.Grazing significantly affected soil greenhouse gas emissions.Heavy grazing significantly increased soil CO2 emission fluxes and significantly decreased soil CH4 uptake fluxes in desert grasslands（P＜0.05）.In addition,soil CO2 gas isotope values increased significantly（P＜0.05）under heavy grazing compared to the control,and showed an increasing trend for soil CH4 gas isotopes.4.Grazing had a significant effect（P＜0.05）on soil environmental factors in desert grasslands.Compared to the control,heavy grazing significantly reduced the soil water content and had an increasing trend on soil temperature.Grazing regulates carbon soil greenhouse gas emissions and uptake by altering soil environmental factors,with soil CO2fluxes significantly and positively correlated with soil water content and soil temperature,and soil CH4 fluxes significantly and negatively correlated with soil water conten

Mots clés : Desert grassland ;Grazing intensity ;Carbon dioxide ;Methane;Stabilized carbon isotopes ;

Présentation (CNKI)