Les sols sont la principale composantede l’écosystème terrestre et le plus grand réservoir de carbone organique sur Terre, étant très réactifs aux perturbations humaines et aux changements climatiques. Malgré leur importance dans les réservoirs de carbone, la dynamique du carbone des sols est une source importante d'incertitudes pour les prévisions climatiques futures. Le but de la thèse était d'explorer différents aspects d’études du carbone des sols (mesures expérimentales, modélisation et évaluation de bases de données) à différentes échelles spatiales (de l'échelle d'un profil à l'échelle globale). Nous avons souligné que l'estimation des stocks globaux de carbone du sol est encore assez incertaine.Par conséquent le rôle du carbone des sols dans la dynamique du climat devient l'une des principales incertitudes dans les modèles du système terrestre utilisés pour prédire les changements climatiques futurs. La deuxième partie de la thèse porte sur la présentation d'une nouvelle version du modèle IPSL-Land Surface appelé ORCHIDEE-SOM, intégrant la dynamique du 14C dans le sol. Plusieurs tests effectués supposent que les améliorations du modèle devraient se focaliser davantage sur une paramétrisation dépendante de la profondeur,principalement pour la diffusion, afin d'améliorer la représentation du cycle global du carbone dans les modèles de surface terrestre, contribuant ainsi à contraindre les prédictions futures du réchauffement climatique. / Soils are the major components ofthe terrestrial ecosystems and the largest organiccarbon reservoir on Earth, being very reactive tohuman disturbance and climate change. Despiteits importance within the carbon reservoirs, soilcarbon dynamics is an important source ofuncertainties for future climate predictions. Theaim of the thesis was to explore different aspectsof soil carbon studies (Experimentalmeasurements, modeling, and databaseevaluation) at different spatial scales (from thescale of a profile to the global scale). Wehighlighted that the estimation of the global soilcarbon stocks is still quite uncertain.Consequently, the role of soil carbon in theclimate dynamics becomes one of the majoruncertainties in the Earth system models (ESMs)used to predict future climate change. Thesecond part of thesis deals with the presentationof a new version of the IPSL-Land SurfaceModel called ORCHIDEE-SOM, incorporatingthe 14C dynamics in the soil. Several tests doneassume that model improvements should focusmore on a depth dependent parameterization,mainly for the diffusion, in order to improve therepresentation of the global carbon cycle inLand Surface Models, thus helping to constrainthe predictions of the future soil organic carbonresponse to global warming.

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The aim of the diploma thesis was to evaluate the content of soil organic carbon in the area of Novohradsko. Soil organic carbon was monitored in its stable (SOC) and labile (WSOC) form, followed by the total organic carbon stock (Cpool). These soil parameters were determined in soils of different land cover types (forest, arable land, grassland) in the area formed by the catchments of Pasecký, Bedřichovský, Váčkový and Veverský stream. Data obtained in 2001, 2007 and 2014 were statistically analysed and the comparison of the data from different catchments was conducted. The results show the impact of different land use on the amount of soil organic carbon. In general, a higher amount of soil organic carbon were found in soils of grassland and forest soils, whereas a lower amounts were found in arable land. The comparison and the time development analysis show that there is a trend of the increase in quantity of stable fraction of soil organic carbon in all categories of land cover over the whole monitored period. The opposite trend of a continuous decrease over the whole of the monitored period in all categories of land cover was observed in amounts of labile fraction of soil organic carbon. It can be said that there is an increase in the stock of a stable fraction of soil organic carbon due to lower losses of the labile fraction of soil organic carbon in forest soils, arable soils and soils of grassland.