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Title:Coupled dynamics of above- and below-ground interactions in the critical zone
Author(s):Quijano, Juan
Director of Research:Kumar, Praveen
Doctoral Committee Chair(s):Kumar, Praveen
Doctoral Committee Member(s):Sivapalan, Murugesu; Porporato, Amilcare; Leakey, Andrew D.; Bernacchi, Carl J.
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):critical zone
energy balance
thermodynamic entropy
Abstract:A detailed understanding of the processes and interactions that occur in the Critical Zone (CZ) is extremely important. It will help us to sustainably manage natural resources while maintaining a balance between the natural dynamics and anthropogenic modifications. In this study I have developed a predictive understanding of the above- and below-ground interactions that occur in the CZ in the light of different dynamics involving water, carbon, nitrogen, energy, and thermodynamic entropy fluxes. In addition, these processes are analyzed within a multi-species framework where different plant species coexist and share resources. Coexistence of species originates competitive and mutualistic interactions that impact the fluxes described above. This study represents the first numerical attempt that simulates all these dynamics using a common framework and numerical formulation. The above- and below-ground dynamics were analyzed using data from three Ameriflux Sites: (i) Blodgett Ameriflux Site, California, US, (ii) Tapajos Km 67, Para, Brazil, and (iii) Harvard Forest, Massachusetts, US. The ecosystems in these sites have different species composition, and experience different climatic conditions. In addition, these sites have more than three years of records, and detailed experimental research has been performed by others which facilitates the validation of the simulations performed in this study. I analyzed the role of vegetation structure and composition on the fluxes of water, energy, and entropy. Our simulations recognized mutualistic and competitive interactions for water resources that impacted the ecosystem productivity, and the energy and water balance in the land surface. These results suggest plant species composition is an important factor that regulates the fluxes of water in the soil and should be included in ecohydrological models. Long term simulations demonstrate that plants impact the below-ground biogeochemical cycling of nitrogen and carbon, not only by litter drop, as had been recognized in previous ecological experimental studies, but also from their impact on the water and energy balance of the surface. Alteration of energy and water balance under different vegetation structure also represents significant differences in the budget of entropy, which increases with leaf area index (LAI) and is constrained by the below-ground capacity (e.g. deep roots) to sustain high rates of latent heat (LE) fluxes. Lastly, I explored the production of entropy as a general organizing principle that explains the structure, composition, and functioning of ecosystems resembling different levels of organization in the CZ. I found there is no significant difference in the total entropy production between the different levels of organization. However, the diurnal patterns of entropy production and the forms of the outgoing entropy flux varies considerably. There is an important trade off between the dissipation of energy in the forms of LE and longwave (LW). LE enhances entropy production by reducing the surface effective temperature while LW enhances the production of entropy because it has higher levels of entropy than the LE fluxes. I found this trade off changes according to the level of organization that is present in the CZ.
Issue Date:2013-05-24
Rights Information:Copyright 2013 Juan Quijano
Date Available in IDEALS:2013-05-24
Date Deposited:2013-05

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