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Simulació de fluxos de carboni terrestres mitjançant teledetecció i modelització d'ecosistemes

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Valencià Castellano

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IMPORTANT: Aquest repositori està en una versió antiga des del 3/12/2023. La nova instal.lació está en https://roderic.uv.es/

Simulació de fluxos de carboni terrestres mitjançant teledetecció i modelització d'ecosistemes

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dc.contributor.advisor	Gilabert Navarro, María Amparo
dc.contributor.advisor	Maselli, Fabio
dc.contributor.author	Sánchez-Ruiz, Sergio
dc.contributor.other	Departament de Física de la Terra i Termodinàmica	es_ES
dc.date.accessioned	2018-11-13T11:11:27Z
dc.date.available	2018-11-14T05:45:06Z
dc.date.issued	2018	es_ES
dc.date.submitted	08-11-2018	es_ES
dc.identifier.uri	http://hdl.handle.net/10550/67936
dc.description.abstract	The main goal of this thesis is the establishment of a framework to analyze the Spanish forest ecosystems in terms of their role in the carbon cycle. In particular, the carbon fluxes that they exchange with atmosphere are modeled to evaluate their potential as carbon sinks and biomass reservoirs. Gross fluxes are estimated by a production efficiency model relying on the Monteith’s approach. The emphasis is put in characterizing the water stress effects on the light use efficiency and, eventually, on the GPP. Six alternatives are evaluated. Among them, the ones using the ratio between the MODIS actual and potential evapotranspiration, and the soil moisture from SMOS demonstrate that it is possible to characterize the water stress on GPP using only remote sensing products. Daily images of GPP are calculated and used as a reference in the rest of the thesis. The reference GPP is then used to calibrate and validate a semi-empirical model for the estimation of annual GPP. This model is a simplification of the Monteith approach that relies on a linear relationship between GPP and a PAR-weighted vegetation index (VI). This semi-empirical model can be used to estimate the annual GPP from commonly available VI images and a representative PAR, which does not require actual meteorological data. Therefore, inputs and computing time are considerably reduced. NDVI and EVI are tested. EVI does not need a land cover map, reducing the number of inputs even more. NDVI allows the elaboration of climatic studies that require long time series. Ecosystem respirations are simulated through Biome-BGC. A methodology to calibrate the rooting depth parameter, critical to the simulation of the water balance, is developed. The optimal rooting depth is obtained by comparing the reference GPP with the one simulated by Biome-BGC. The methodology is first tested in 4 validation sites and then extended to the whole study area. As a result, daily GPP maps and an optimal rooting depth map are obtained. Reference GPP and optimized respirations are used to calculate net fluxes. However, both GPP and respiration must be previously corrected. The first one because it represents the contribution of all the vegetation present in the considered area, not only the one from the forests. The second one because Biome-BGC works on equilibrium conditions and does not represent the actual state of the ecosystem. To do so, the necessary information layer, a growing stock map, is produced by the combination of the Third Spanish National Forest Inventory data (more than 50000 plot along the 1997-2007 period) and Landsat-5 TM and Landsat-7 ETM+ imagery (more than 8000 scenes covering the whole study area during the inventory period). Finally, preliminary net fluxes resulting from the corrected GPP and respirations are presented and validated.	en_US
dc.description.abstract	The main goal of this thesis is the establishment of a framework to analyze the Spanish forest ecosystems in terms of their role in the carbon cycle. In particular, the carbon fluxes that they exchange with atmosphere are modeled to evaluate their potential as carbon sinks and biomass reservoirs. Gross fluxes are estimated by a production efficiency model relying on the Monteith’s approach. The emphasis is put in characterizing the water stress effects on the light use efficiency and, eventually, on the GPP. Six alternatives are evaluated. Among them, the ones using the ratio between the MODIS actual and potential evapotranspiration, and the soil moisture from SMOS demonstrate that it is possible to characterize the water stress on GPP using only remote sensing products. Daily images of GPP are calculated and used as a reference in the rest of the thesis. The reference GPP is then used to calibrate and validate a semi-empirical model for the estimation of annual GPP. This model is a simplification of the Monteith approach that relies on a linear relationship between GPP and a PAR-weighted vegetation index (VI). This semi-empirical model can be used to estimate the annual GPP from commonly available VI images and a representative PAR, which does not require actual meteorological data. Therefore, inputs and computing time are considerably reduced. NDVI and EVI are tested. EVI does not need a land cover map, reducing the number of inputs even more. NDVI allows the elaboration of climatic studies that require long time series. Ecosystem respirations are simulated through Biome-BGC. A methodology to calibrate the rooting depth parameter, critical to the simulation of the water balance, is developed. The optimal rooting depth is obtained by comparing the reference GPP with the one simulated by Biome-BGC. The methodology is first tested in 4 validation sites and then extended to the whole study area. As a result, daily GPP maps and an optimal rooting depth map are obtained. Reference GPP and optimized respirations are used to calculate net fluxes. However, both GPP and respiration must be previously corrected. The first one because it represents the contribution of all the vegetation present in the considered area, not only the one from the forests. The second one because Biome-BGC works on equilibrium conditions and does not represent the actual state of the ecosystem. To do so, the necessary information layer, a growing stock map, is produced by the combination of the Third Spanish National Forest Inventory data (more than 50000 plot along the 1997-2007 period) and Landsat-5 TM and Landsat-7 ETM+ imagery (more than 8000 scenes covering the whole study area during the inventory period). Finally, preliminary net fluxes resulting from the corrected GPP and respirations are presented and validated.	en
dc.format.extent	240 p.	es_ES
dc.language.iso	ca	en
dc.subject	remote sensing	en
dc.subject	carbon fluxes	en
dc.title	Simulació de fluxos de carboni terrestres mitjançant teledetecció i modelització d'ecosistemes	ca
dc.type	doctoral thesis	es_ES
dc.subject.unesco	UNESCO::CIENCIAS DE LA TIERRA Y DEL ESPACIO	es_ES
dc.subject.unesco	UNESCO::FÍSICA	es_ES
dc.embargo.terms	0 days	es_ES