P. Serrano-Ortiz

The biogeochemical role of Actinobacteria in Altamira Cave, Spain

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.

Variations in daytime net carbon and water exchange in a montane shrubland ecosystem in southeast Spain

Carbon and water fluxes in a semiarid shrubland ecosystem located in the southeast of Spain (province of Almería) were measured continuously over one year using the eddy covariance technique. We examined the influence of environmental variables on daytime (photosynthetically active photons, FP >10 µmol m−2 s−1) ecosystem gas exchange and tested the ability of an empirical eco-physiological model based on FP to estimate carbon fluxes over the whole year. The daytime ecosystem fluxes showed strong seasonality. During two solstitial periods, summer with warm temperatures (>15 °C) and sufficient soil moisture (>10 % vol.) and winter with mild temperatures (>5 °C) and high soil moisture contents (>15 % vol.), the photosynthetic rate was higher than the daytime respiration rate and mean daytime CO2 fluxes were ca. −1.75 and −0.60 µmol m−2 s−1, respectively. Daytime evapotranspiration fluxes averaged ca. 2.20 and 0.24 mmol m−2 s−1, respectively. By contrast, in summer and early autumn with warm daytime temperatures (>10 °C) and dry soil (<10 % vol.), and also in mid-winter with near-freezing daytime temperatures the shrubland behaved as a net carbon source (mean daytime CO2 release of ca. 0.60 and 0.20 µmol m−2 s−1, respectively). Furthermore, the comparison of water and carbon fluxes over a week in June 2004 and June 2005 suggests that the timing—rather than amount—of spring rainfall may be crucial in determining growing season water and carbon exchange. Due to strongly limiting environmental variables other than FP, the model applied here failed to describe daytime carbon exchange only as a function of FP and could not be used over most of the year to fill gaps in the data.

Cave ventilation is influenced by variations in the CO 2 -dependent virtual temperature

This research was funded by the Andalusian regional government project GEOCARBO (P08- RNM-3721) and GLOCHARID, including European Union ERDF funds, with support from Spanish Ministry of Science and Innovation projects CarboredII (CGL2010-22193-C04-02), SOILPROF (CGL2011- 15276-E) and CARBORAD (CGL2011-27493), as well as the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 244122.

Winds induce CO2 exchange with the atmosphere and vadose zone transport in a karstic ecosystem

Andalusian regional government project GEOCARBO [P08-RNM-3721]; European Union ERDF funds; Spanish Ministry of Science and Innovation project SOILPROF [CGL2011-15276-E]; Spanish Ministry of Science and Innovation project CARBORAD [CGL2011-27493]; Spanish Ministry of Science and Innovation project GEISpain [CGL2014-52838-C2-1-R]; Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, DIESEL project [625988]

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

The consistency of eddy-covariance measurements is often evaluated in terms of the degree of energy balance closure. Even over sloping terrain, instrumentation for measuring energy balance components is commonly installed horizontally, i.e. perpendicular to the geo-potential gradient. Subsequently, turbulent fluxes of sensible and latent heat are rotated perpendicular to the mean streamlines using tilt-correction algorithms. However, net radiation

From microhabitat to ecosystem: identifying the biophysical factors controlling soil CO2 dynamics in a karst shrubland: Biophysical factors controlling soil CO2 dynamics

(R_{\mathrm{n}})

Hidden, abiotic CO2 flows and gaseous reservoirs in the terrestrial carbon cycle: Review and perspectives

(Rn) and soil heat fluxes (G) are treated differently, and typically only