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Orientador: Wilson de F. Jardim / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-07-20T06:33:10Z (GMT). No. of bitstreams: 1 Lombardi_AnaTeresa_D.pdf: 3834283 bytes, checksum: b32a909c15c8badb9e078a92bd38c19b (MD5) Previous issue date: 1995 / Doutorado

Thesis (Ph. D.)--University of Adelaide, Dept. of Soil Science, 1997. / Copies of author's previously published works inserted. Includes bibliographical references (leaves 260-299).

Soil organic matter (SOM) is important to the environment. Its carbon content is the largest reservoir in the global terrestrial ecosystem and decomposition of it emits greenhouse gases including CO2, CH4 and N2O. The current status of GB SOM is under debate because recent observation programmes suggested different findings. Independent and parallel computer simulations of SOM dynamics could provide useful information for the science debate and that is the objective of this thesis. A newly coupled land surface -- SOM dynamics model, JULES-ECOSSE, was applied for the computer simulations in this Ph.D study. The details of this coupled model are described in Chap. 2. Before the simulation studies in Chap. 6, three other studies were done to (1) derive a new algebraic method to spin up the content of SOM pools such that their equilibrium values can be found efficiently; (2) evaluate the model's capability in simulating various gas fluxes using the observed data from the NitroEurope project. This evaluation study provided important information about how well the model works in different aspects; (3) find better performing parameter sets for GB vegetation using a factorial experiment as sensitivity analysis followed by a multi-objective calibration scheme. After the aforementioned studies, the model was applied in Chap. 6 to answer three environmental questions. The simulations suggest that climate change over 1978-2007 had minor impacts on GB SOM, however the future impacts of climate change could potentially be big. The exact magnitudes vary between ecosystems and will also depend on the representative concentration pathway that the world will follow. Inclusion of other observed environmental changes (i.e. changing age structure and composition in woodlands, nitrogen eutrophication effect, changing soil pH and its impact on DOC mobility, soil erosion, non-equilibrium status of SOM) could better match observed changes with simulated changes. This suggests that they could be the candidates explaining the recent observed trends in GB SOM.

Thesis (Ph. D.)--University of Washington, 1985. / Vita. Bibliography: leaves [127]-139.

Zugl.: Giessen, Univ., Diss., 2009

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Microbial metabolic activity in the hypolimnia and sediments of lakes drives the recycling of organic matter both through mineralization and the production of microbial biomass, which may be utilized by grazers. A correction factor was developed based on the water content of sediment samples that corrects sediment bacteria microscopic counts for masking due to sediment particles. Using this correction factor, it was found that sediment bacterial biomass in 22 lakes was positively related to an indicator of the rate of allochthonous organic matter input to lakes. However, the total hypolimnetic carbon mineralization rate of lakes, which integrates both sediment and hypolimnetic water column mineralization, was found to be driven mainly by phytoplankton carbon and to occur mainly in the hypolimnetic water column. Indeed, various hypolimnetic and sediment catabolic processes were found to show a strong positive relationship with indicators of autochthonous organic matter standing stocks and production. In no cases were the processes significantly positively correlated with allochthonous organic matter standing stocks. Results of this research show that autochthonous primary production drives carbon recycling in the hypolimnetic water column, with the ultimate fate of this production being determined principally by the hypolimnetic thickness. The main fate of allochthonous organic matter in lakes is to become a major component of sediment organic matter where it likely drives a much slower catabolism due to its recalcitrance.

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Zugl.: Hannover, Univ., Diss., 2007