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dc.contributor.authorEl-Madany, Tarek S.
dc.contributor.authorReichstein, Markus
dc.contributor.authorPerez-Priego, Oscar
dc.contributor.authorCarrara, Arnaud
dc.contributor.authorMoreno, Gerardo
dc.contributor.authorMartín, M. Pilar
dc.contributor.authorPacheco-Labrador, Javier
dc.contributor.authorWohlfahrt, Georg
dc.contributor.authorNieto, Hector
dc.contributor.authorWeber, Ulrich
dc.contributor.authorKolle, Olaf
dc.contributor.authorLuo, Yun-Peng
dc.contributor.authorCarvalhais, Nuno
dc.contributor.authorMigliavacca, Mirco
dc.contributor.otherProducció Vegetalca
dc.date.accessioned2018-12-19T11:58:26Z
dc.date.available2018-12-19T11:58:26Z
dc.date.issued2018-07-25
dc.identifier.citationEl-Madany, Tarek S., Markus Reichstein, Oscar Perez-Priego, Arnaud Carrara, Gerardo Moreno, M. Pilar Martín, and Javier Pacheco-Labrador et al. 2018. "Drivers Of Spatio-Temporal Variability Of Carbon Dioxide And Energy Fluxes In A Mediterranean Savanna Ecosystem". Agricultural And Forest Meteorology 262: 258-278. Elsevier BV. doi:10.1016/j.agrformet.2018.07.010.ca
dc.identifier.issn0168-1923ca
dc.identifier.urihttp://hdl.handle.net/20.500.12327/124
dc.description.abstractTo understand what is driving spatial flux variability within a savanna type ecosystem in central Spain, data of three co-located eddy covariance (EC) towers in combination with hyperspectral airborne measurements and footprint analysis were used. The three EC systems show consistent, and unbiased mass and energy fluxes. Nevertheless, instantaneous between-tower flux differences i.e. paired half hourly fluxes, showed large variability. A period of 13 days around an airborne hyperspectral campaign was analyzed and proved that betweentower differences can be associated to biophysical properties of the sampled footprint areas. At high photosynthetically active radiation (PAR) net ecosystem exchange (NEE) was mainly controlled by chlorophyll content of the vegetation (estimated through MERIS Terrestrial Chlorophyll Index (MTCI)), while sensible heat flux (H) was driven by surface temperature. The spatial variability of biophysical properties translates into flux variability depending on the location and size of footprints. For H, negative correlations were found with surface temperature for between-tower differences, and for individual towers in time, meaning that higher H was observed at lower surface temperatures. High aerodynamic conductance of tree canopies reduces the canopy surface temperature and the excess energy is relieved as H. Therefore, higher tree canopy fractions yielded to lower surface temperatures and at the same time to higher H. For NEE, flux differences between towers were correlated to differences in MTCI of the respective footprints, showing that higher chlorophyll content of the vegetation translates into more photosynthetic CO2 uptake, which controls NEE variability. Between-tower differences of latent heat fluxes (LE) showed no consistent correlation to any vegetation index (VI), or structural parameter e.g. tree-grass-fraction. This missing correlation is most likely caused by the large contribution of soil evaporation to ecosystem LE, which is not captured by any of the biophysical and structural properties. To analyze if spatial heterogeneity influences the uncertainty of measured fluxes three different measures of uncertainty were compared: the standard deviation of the marginal distribution sampling (MDS), the two-towerapproach (TTA), and the variance of the covariance (RE). All three uncertainty estimates had similar means and distributions at the individual towers while the methods were significantly different to each other. The uncertainty estimates increased from RE over TTA to MDS, indicating that different components like space, time, meteorology, and phenology are factors, which affect the uncertainty estimates. Differences between uncertainty estimates from the RE and TTA indicate that spatial heterogeneity contributes significantly to the ecosystem-flux uncertaintyca
dc.format.extent21ca
dc.language.isoengca
dc.publisherElsevierca
dc.relation.ispartofAgricultural and Forest Meteorologyca
dc.rightsAttribution 4.0 Internationalca
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/*
dc.titleDrivers of spatio-temporal variability of carbon dioxide and energyfluxes ina Mediterranean savanna ecosystemca
dc.typeinfo:eu-repo/semantics/articleca
dc.description.versioninfo:eu-repo/semantics/publishedVersionca
dc.rights.accessLevelinfo:eu-repo/semantics/openAccess
dc.embargo.termscapca
dc.relation.projectIDMINECO/Programa Nacional de Proyectos de Investigación Fundamental/CGL2012-34383/ES/SEGUIMIENTO DE FLUJOS DE AGUA Y CARBONO MEDIANTE TELEDETECCION EN ECOSISTEMAS MEDITERRANEOS DE DEHESA/FLUXPECca
dc.subject.udc504 - Ciències del medi ambientca
dc.identifier.doihttps://doi.org/10.1016/j.agrformet.2018.07.010ca
dc.contributor.groupÚs Eficient de l'Aigua en Agriculturaca


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