Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Le radiocarbone (14C) et le tritium (3H) sont libérés dans l'environnement de manière naturelle et par les activités nucléaires. Les rejets devant perdurer pendant les prochaines décennies, il est primordial de prévoir leur devenir et leur temps de résidence dans les sols. L'objectif de cette thèse est de proposer une prévision quantitative et une modélisation simple du devenir de 14C et 3H dans les matières organiques du sol (MOS). L'originalité de ce travail est double: nous faisons l'hypothèse que l'incorporation et le devenir des atomes d'hydrogène non-échangeable (HNE) dans le sol sont couplés à la dynamique du carbone; l'approche choisie est le traçage naturel ou artificiel par les isotopes stables 13C et 2H.A travers le traçage naturel par le 13C in situ, nous avons quantifié le carbone récemment incorporé par la végétation sur quelques décennies. Nous avons alors adapté le modèle RothC à la dynamique du C profond des sols. Cela nous a permis de prévoir que 10% du C persisteront pendant plusieurs siècles dans les couches profondes. Les expériences croisées d'incubation de composés marqués en 13C et 2H nous a permis de montrer que l’activité microbienne est le moteur de l’incorporation d’hydrogène de l’eau dans les MOS et nous a permis d'établir la stœchiométrie CH des biotransformations. Ces expérimentations ont permis de proposer un modèle de la dynamique couplée de C et H des MOS à court et moyen terme (décennies). Une méta-analyse des corrélations entre les teneurs en 13C et 14C de sols mondiaux nous a permis de démontrer que l'enrichissement en 13C des MOS peut être expliqué en totalité par le rapport 13C/12C de la végétation dont elles sont issues. / Radiocarbon (14C) and tritium (3H) are naturally released into the environment but also through nuclear activities. The releases are expected to persist for the next decades, it is important to predict their fate and their residence time in soils. The objective of this thesis is to propose a quantitative prediction and a simple modeling of the fate of 14C and 3H in soil organic matter (SOM). The originality of this work is twofold: first, we hypothesize that the incorporation and fate of NEH atoms in the soil are coupled to the carbon dynamics. Second, we chose to trace carbon and hydrogen by natural or artificial 13C and 2H tracing.Through natural in situ 13C tracing, we quantified the carbon recently incorporated by vegetation in few decades. Deep horizons contain a large part of this carbon (typically 20 to 30%). We adapted the RothC model to the deep soil C dynamics. This allowed us to predict that 10% of C will persist for several centuries in the deeper layers. The labelling experiments showed that the microbial activity is driving the incorporation of hydrogen from water into SOM, and allowed us to establish the CH stoichiometry of biotransformations. These experiments were a mean to propose a model of the coupled C and H dynamics of the SOM in the short and medium term (decades). The results of this thesis contribute as well to the improvement of the interpretation of natural abundances in 13C and 2H stable isotopes. A meta-analysis of the correlations between the 13C and 14C concentrations of global soils has demonstrated that the 13C enrichment of deep organic matter can be fully explained by the 13C/12C ratio of the vegetation from which they are derived.

No description available.

Soil organic matter (SOM) decomposition and formation is an important climate feedback, with the potential to amplify or offset climate forcing. To understand the fate of soil carbon (C) stores and fluxes (i.e., soil respiration) under future climate it is necessary to investigate responses across spatial and temporal scales, from the ecosystem to the molecular level, from diurnal to decadal trends. Moreover, it is important to question the assumptions and paradigms that underlie apparently paradoxical evidence to reveal the true nature of soil-climate feedbacks. My dissertation includes research into the response of soil respiration in Pacific Northwest prairies to warming and wetting along a natural regional climate gradient (Chapter II), and then delves deeper into the mechanisms underlying SOM decomposition and formation, examining the temperature sensitivity of SOM decomposition of prairie soils that were experimentally warmed for ~2 yr, and a forest soil in which litter-inputs were manipulation for 20 yr (Chapter III), and finally testing soil C cycling dynamics, including mineral-associated C pools, decomposition dynamics, and the molecular nature of SOM itself, under litter-manipulation in order to understand the controls on SOM formation and mineralization (Chapter IV). This dissertation includes previously published and unpublished coauthored material; see the individual chapters for a list of co-authors, and description of contributions.

The aim of the theses was to describe soil organic matter changes in model landscape Stropnice subcatchments that have different biotopes and agricultural and forest management.Particular aims were: 1) to determine the link between landuse, soil environment changes and catchment matter losses. 2)to experimentally prove the water regime impact on carbon and other substances losses during and between vegetation seasons.

The work was focused on the research of soil organic matter content and quality of selected forest soils. In the theoretical part of the thesis there were described in detail terms important to understand the given topic. In the practical part soil probes were excavated and soil samples were taken from individual horizons. The probing was carried out in two stands with a different representation of trees (forest type 0P, district Hodějov, Forest Management Třeboň, ownership of the Czech Republic, right to manage Forests of the Czech Republic, etc.). In the first case, it was a vegetation of deciduous trees (vegetation 356D12), in the second one with a vegetation of coniferous trees (356E11). In the laboratory of the Department of Agroecosystems of the Faculty of Agriculture of the University of South Bohemia in České Budějovice soil samples were modified and further examined in terms of the quantity and quality of soil organic matter. A new method, proposed by the collections of authors Kopecký, Kolář, Borová-Batt (2016), was used to compare the quality of the primary soil organic matter in individual samples by determining the velocity constant of the oxidation of the primary soil organic matter. The humus content was then determined and the degree of humification was calculated. The results show that the monitored parameters differ considerably in individual soil horizons. Significant differences were also observed when comparing soils of coniferous and deciduous stands. A considerable difference can be seen, for example, in the organic carbon content at the top horizons. For example, at the Ahe horizon, the total organic carbon content was found to be 39.71 % for coniferous soil, while in the leafy soil the carbon content at the same horizon was only 7.06 %. The highest value of the velocity constant to oxidation of the primary soil organic matter, which indicates its highest quality, was recorded at the Ep horizon (9-20 cm depth) of the deciduous soil probe.