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Effets du chaulage sur le fontionnement de l'écosystème prairial en moyenne montagne

Abstract : The development of sustainable agriculture requires greater understanding of the impact of management practices on agroecosystem functioning, and on the ecosystem services provided by these agroecosystems. Representing nearly 68% of world's agricultural surfaces and contributing to the livelihoods of more than 800 million people, grasslands are one of the major agroecosystems where optimized agricultural practices are of concern. This PhD focuses on liming, a well-known practice for counteracting soil acidification (due to ongoing natural processes or accelerated by management practices), but which has variable efficiency in permanent grasslands. Indeed, liming effects on grassland are poorly documented and existing studies rarely take into account grassland multifunctionality. My thesis uses an integrated approach to improve the knowledge of liming impacts on grassland functioning. Different types of experiments – in the field (in situ), in semi-controlled conditions (mesocosms) and laboratory soil incubations (microcosms) – were used to study liming effects on different grassland compartments (vegetation, microorganisms, soil) along with possible interacting factors. Liming effectively increased soil pH in all the experiments. However, improving pH status did not always lead to greater forage production or increases in microbial and root biomass. My results showed that liming can enhance greenhouse gas emissions through several pathways (reemission of lime-derived carbon or stimulation of carbon mineralization), but may also reduce CO2 emissions from ecosystem respiration. Collectively, my findings emphasize the importance of pedoclimatic conditions for liming impacts on permanent grasslands and highlight the difficulty of upscaling liming effects, particularly on forage production and greenhouse gas emissions. The efficiency of liming appears to depend on the type and dose of soil improvers and can also interact with other management practices such as nitrogen fertilization and management intensification.
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Iris Lochon. Effets du chaulage sur le fontionnement de l'écosystème prairial en moyenne montagne. Sciences agricoles. Université Clermont Auvergne, 2018. Français. ⟨NNT : 2018CLFAC053⟩. ⟨tel-02087951⟩

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