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sur le développement des zones arides et semi-arides

Titre : Effects of Different Grazing Intensities on Ecosystem Carbon Exchange in Stipa Breviflora Desert Steppe

Auteur : 王冰莹

Grade : Master 2022

Université : Inner Mongolia Agricultural University

Résumé
In recent years,with gradually increased global climate warming,how to effectively control greenhouse gas emissions,sequester CO2and slow down climate change is not only a major scientific issue,but also the only way for China to achieve carbon neutrality by 2060.Grassland ecosystem carbon exchange plays an important role in the global carbon cycle.Grassland is disturbed and affected by grazing,which leads to many uncontrollable changes in ecosystem carbon exchange.Based on the long-term controlled grazing experiment,this study adopted a completely randomized block design and set four grazing intensities:no grazing（CK）,light grazing（LG）,moderate grazing（MG）and heavy grazing（HG）.The Li-6400 portable photosynthetic instrument and open circuit Li-8100soil carbon flux meter were used to observe the net ecosystem CO2exchange and soil respiration under four grazing intensities.At the same time,the aboveground standing crop of grassland plants,the total carbon and nitrogen content of plant community,belowground biomass and soil physical and chemical properties were measured.The purpose of this study was to investigate the mechanism of carbon sequestration and the main factors affecting carbon exchange in stipa breviflora desert steppe ecosystem under different grazing intensities.The main conclusions are as follows:1.The aboveground standing crop of perennial forbs,shrubs,semi-shrubs and annuals and biennials decreased significantly with the increase of grazing intensity,but there was no significant difference in that of perennial grasses among different grazing intensities.The belowground net primary productivity was the highest in MG plots,and the lowest in HG plots.The belowground standing crop decreased significantly with the increase of grazing intensity.2.The total carbon content of the aboveground part of the plant community decreased significantly in HG plots,and the total nitrogen content decreased significantly in MG area,and the carbon nitrogen content ratio was significant different under different grazing intensities.Grazing intensities significantly affected soil organic carbon content,soil ammonium nitrogen content and soil moisture content.3.During the growing season,the Stipa breviflora desert steppe was in a carbon absorption as a whole,and the ecosystem carbon exchange decreases significantly with the increase of grazing intensity.The grazing intensity and annual change significantly affect the ecosystem carbon exchange.4.The change of aboveground standing crop mainly determined the change of net ecosystem CO2exchange rate of Stipa breviflora desert steppe.The aboveground standing crop of shrubs and semi-shrubs was the main factor affecting net ecosystem CO2exchange.At the same time,the change of standing crop on perennial grasses and total nitrogen content of plant community also affected the net carbon absorption.Nitrogen was the main nutrient element regulating soil respiration.At the same time,the accumulation of belowground standing crop and the change of soil organic carbon content also affected the change of soil respiration rate

Mots clés : Stipa breviflora desert steppe ;Grazing intensity ;Net ecosystem CO2 exchange ;Soil respiration ;

Présentation (CNKI)