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Cuezva S.,University of Alicante | Fernandez-Cortes A.,CSIC - National Museum of Natural Sciences | Porca E.,Institute Recursos Naturales y Agrobiologia | Pasic L.,University of Ljubljana | And 7 more authors.
FEMS Microbiology Ecology | Year: 2012

The walls and ceiling of Altamira Cave, northern Spain, are coated with different coloured spots (yellow, white and grey). Electron microscopy revealed that the grey spots are composed of bacteria and bioinduced CaCO 3 crystals. The morphology of the spots revealed a dense network of microorganisms organized in well-defined radial and dendritic divergent branches from the central area towards the exterior of the spot, which is coated with overlying spheroidal elements of CaCO 3 and CaCO 3 nest-like aggregates. Molecular analysis indicated that the grey spots were mainly formed by an unrecognized species of the genus Actinobacteria. CO 2 efflux measurements in rocks heavily covered by grey spots confirmed that bacteria-forming spots promoted uptake of the gas, which is abundant in the cave. The bacteria can use the captured CO 2 to dissolve the rock and subsequently generate crystals of CaCO 3 in periods of lower humidity and/or CO 2. A tentative model for the formation of these grey spots, supported by scanning electron microscopy and transmission electron microscopy data, is proposed. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.


Foyo-Moreno I.,University of Granada | Foyo-Moreno I.,Centro Andaluz Of Medio Ambiente | Alados I.,University of Malaga | Anton M.,University of Extremadura | And 6 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2014

Under cloudless conditions aerosols are the main atmospheric components responsible for direct effects on solar radiation. Measurements of aerosol optical properties along with simultaneous measurements of solar irradiances (global -G- and diffuse -D-) were recorded at an urban site (Granada, Spain) to characterize the radiative effect of atmospheric aerosols from 2006 to 2008. The selection of cloudless conditions was made considering cases with 0 oktas. To avoid cloud contamination, a restricted data set with clearness index larger than 0.65 and maximum D of 200-W/m2 was used. The analysis was performed evaluating G, D, and IN (direct normal irradiance) and the ratios between them in association with aerosol optical depth (AOD) at 675-nm. Results show an aerosol forcing efficiency of -279-±-21-W/m2 per unit of AOD at 675-nm at 15° solar zenith angle and a maximum value in June for monthly mean aerosol radiative forcing of -23-±-7-W/m 2. Large dependency was shown of the ratios D/G and D/IN which increased with increasing AOD, while IN/G decreased. On the other hand, the ratio D/IN was the most reliable parameter to estimate AOD with a coefficient of determination of 0.94; the empirical relationship obtained was validated using an independent data set obtaining 2.5% mean bias deviation and 13.5% root-mean-square deviation. This relationship constitutes an alternative tool for estimating AOD from routine irradiance measurements available from numerous radiometric stations worldwide. Key Points Estimate of aerosol optical depth from available radiometric measurements Combined characterization of irradiance and aerosol data at an urban location Aerosol radiative forcing is calculated only from global irradiance data © 2014. American Geophysical Union. All Rights Reserved.


Sanchez-Canete E.P.,EEZA | Sanchez-Canete E.P.,Centro Andaluz Of Medio Ambiente | Serrano-Ortiz P.,EEZA | Serrano-Ortiz P.,Centro Andaluz Of Medio Ambiente | And 5 more authors.
Geophysical Research Letters | Year: 2011

Recent studies of carbonate ecosystems suggest a possible contribution of subterranean ventilation to the net ecosystem carbon balance. However, both the overall importance of such CO2 exchange processes and their drivers remain unknown. Here we analyze several dry-season episodes of net CO 2 emissions to the atmosphere, along with soil and borehole CO 2 measurements. Results highlight important events where rapid decreases of underground CO2 molar fractions correlate well with sizeable CO2 release to the atmosphere. Such events, with high friction velocities, are attributed to ventilation processes, and should be accounted for by predictive models of surface CO2 exchange. © 2011 by the American Geophysical Union.


Serrano-Ortiz P.,CSIC - Estación Experimental De Zonas Áridas | Serrano-Ortiz P.,Centro Andaluz Of Medio Ambiente | Maranon-Jimenez S.,University of Granada | Reverter B.R.,Centro Andaluz Of Medio Ambiente | And 7 more authors.
Forest Ecology and Management | Year: 2011

Post-fire salvage logging is a common silvicultural practice around the world, with the potential to alter the regenerative capacity of an ecosystem and thus its role as a source or a sink of carbon. However, there is no information on the effect of burnt wood management on the net ecosystem carbon balance. Here, we examine for the first time the effect of post-fire burnt wood management on the net ecosystem carbon balance by comparing the carbon exchange of two treatments in a burnt Mediterranean coniferous forest treated by salvage logging (SL, felling and removing the logs and masticating the woody debris) and Non-Intervention (NI, all trees left standing) using eddy covariance measurements. Using different partitioning approaches, we analyze the evolution of photosynthesis and respiration processes together with measurements of vegetation cover and soil respiration and humidity to interpret the differences in the measured fluxes and underlying processes. Results show that SL enhanced CO2 emissions of this burnt pine forest by more than 120gCm-2 compared to the NI treatment for the period June-December 2009. Although soil respiration was around 30% higher in NI during growing season, this was more than offset by photosynthesis, as corroborated by increases in vegetation cover and evapotranspiration. Since SL is counterproductive to climate-change and Kyoto protocol objectives of optimal C sequestration by terrestrial ecosystems, less aggressive burnt wood management policies should be considered. © 2011 Elsevier B.V.


Valenzuela A.,University of Granada | Valenzuela A.,Centro Andaluz Of Medio Ambiente | Olmo F.J.,University of Granada | Olmo F.J.,Centro Andaluz Of Medio Ambiente | And 7 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012

The main goal of this study is to analyze the dependence of columnar aerosol optical and microphysical properties on source region and transport pathways during desert dust intrusions over Granada (Spain) from January 2005 to December 2010. Columnar aerosol properties have been derived from a non-spherical inversion code using the solar extinction measurements and sky radiances in the principal plane. Two classification methods of the African air masses ending at the study location were used by means of the HYSPLIT back-trajectories analysis. The first one, based on desert dust origin sources, discriminated the optical properties only for sector B (corresponding to western Sahara, northwest Mauritania and southwest Algeria). The particles present marked absorbing properties (low value of single scattering albedo at all wavelengths) during the desert dust events when the air masses were transported from sector A (north Morocco, northwest Algeria). This result may be related to the mixing of desert dust with anthropogenic pollutants from North African industrial areas in addition to the mixing with local anthropogenic aerosol and pollutants transported from European and Mediterranean areas. The second classification method was based on a statistics technique called cluster classification which allows grouping the air masses back trajectories with similar speed and direction of the trajectory. This method showed slight differences in the optical properties between the several transport pathways of air masses. High values of the aerosol optical depth and low mean values of the Angstrm parameter were associated with longer transport pathways over desert dust sources and slowly moving air masses. Both classification methods showed that the fine mode was mixed with coarse mode, being the fine mode fraction smaller than 55%. © 2012 by the American Geophysical Union.


Scott R.L.,U.S. Department of Agriculture | Serrano-Ortiz P.,CSIC - Estación Experimental De Zonas Áridas | Serrano-Ortiz P.,Centro Andaluz Of Medio Ambiente | Domingo F.,CSIC - Estación Experimental De Zonas Áridas | And 3 more authors.
Journal of Arid Environments | Year: 2012

Comparing biosphere-atmosphere carbon exchange across monsoon (warm-season rainfall) and Mediterranean (cool-season rainfall) regimes can yield information about the interaction between energy and water limitation. Using data collected from eddy covariance towers over grass and shrub ecosystems in Arizona, USA and Almeria, Spain, we used net ecosystem carbon dioxide exchange (NEE), gross ecosystem production (GEP), and other meteorological variables to examine the effects of the different precipitation seasonality. Considerable crossover behavior occurred between the two rainfall regimes. As expected in these usually water-limited ecosystems, precipitation magnitude and timing were the dominant drivers of carbon exchange, but temperature and/or light also played an important role in regulating GEP and NEE at all sites. If significant rainfall occurred in the winter at the Arizona sites, their behavior was characteristically Mediterranean whereby the carbon flux responses were delayed till springtime. Likewise, the Spanish Mediterranean sites showed immediate pulse-like responses to rainfall events in non-winter periods. The observed site differences were likely due to differences in vegetation, soils, and climatology. Together, these results support a more unified conceptual model for which processes governing carbon cycling in semiarid ecosystems need not differ between warm-season and cool-season rainfall regimes. © 2012.


Hamerlynck E.P.,U.S. Department of Agriculture | Scott R.L.,U.S. Department of Agriculture | Sanchez-Canete E.P.,CSIC - Estación Experimental De Zonas Áridas | Sanchez-Canete E.P.,Centro Andaluz Of Medio Ambiente | Barron-Gafford G.A.,University of Arizona
Journal of Geophysical Research: Biogeosciences | Year: 2013

Despite their prevalence, little attention has been given to quantifying arid land soil and ecosystem carbon fluxes over prolonged, annually occurring dry periods. We measured soil [CO2] profiles and fluxes (F s) along with volumetric soil moisture and temperature in bare interplant canopy soils and in soils under plant canopies over a three-month hot and dry period in a Chihuahuan Desert shrubland. Nocturnal Fs was frequently negative (from the atmosphere into the soil), a form of inorganic carbon exchange infrequently observed in other deserts. Negative Fs depended on air-soil temperature gradients and were more frequent and stronger in intercanopy soils. Daily integrated ecosystem-level Fs was always positive despite lower daily Fs in intercanopy soils due to nocturnal uptake and more limited positive response to isolated rains. Subsurface [CO2] profiles associated with negative Fs indicated that sustained carbonate dissolution lowered shallow-soil [CO2] below atmospheric levels. In the morning, positive surface Fs started earlier and increased faster than shallow-soil Fs, which was bidirectional, with upward flux toward the surface and downward flux into deeper soils. These dynamics are consistent with carbonate precipitation in conjunction with convection-assisted CO2 outgassing from warming air and soil temperatures and produced a pronounced diurnal Fs temperature hysteresis. We concluded that abiotic nocturnal soil CO2 uptake, through a small carbon sink, modulates dry season ecosystem-level carbon dynamics. Moreover, these abiotic carbon dynamics may be affected by future higher atmospheric carbon dioxide levels and predictions of more prolonged and regular hot and dry periods. Keypoints Desert soils had temperature gradient-dependent nocturnal carbon dioxide uptake Shallow subsurface soil carbon dioxide fluxes were sometimes bidirectional Inorganic carbon dynamics showed clockwise diurnal temperature hysteresis ©2013. American Geophysical Union. All Rights Reserved.

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