Post-fire management effects on sediment (dis)connectivity in Mediterranean forest ecosystems: Channel and catchment response

Forest fires and post-fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ha) affected by a wildfire in 2012 in south-eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post-fire management, and 2 years after the fire including all practices (hillslope barriers, check-dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)-derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AIC_OUT), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non-nested catchments comparable (AIC_N-OUT). The output analysis includes the SC distribution along the catchments and at local scale (929 sub-catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area-specific sediment yield (SSY) at 10 new (built after post-fire practices) concrete check-dams located in the catchments (SSY = 1.94 Mg ha⁻¹ yr⁻¹; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AIC_N-OUT. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post-fire practices that reduced SC ( $\overline{x}$= − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC ( $\overline{x}$= + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AIC_N-OUT at sub-catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AIC_N-OUT. However, the coarse DEM resolution explained the lack of effect of the rock check-dams – located on the secondary channels – on AIC_N-OUT. AIC_N-OUT proved to be a useful tool for decision making in post-fire restoration, but an optimal input data is still necessary to refine calculations.     

Geostatistical Analysis of Inverse Problem Variables: Application to Seismic Tomography

In this article we present a geostatistical approach to the transmission tomographic inverse problem, which is based on consideration of the inverse problem variables (velocity and traveltime errors) as regionalized variables (R.V.). Their structural analysis provides us with a new method to study the geophysical anisotropy of the rock, an important source of a priori information in order to design the anisotropic corrections. The underlying idea is that the geophysical structure can be deduced from the spatial structure of the regionalized variables which result from solving the tomographic problem with an isotropic algorithm. Also, the application of the structural analysis technique to the anisotropic corrected velocity field allows us to characterize the reliability of these corrections (model quality analysis). Geostatistical formalism also provides us with different techniques (parametric and non-parametric) to estimate and even simulate the velocity in the areas where this field has been considered anomalous based on field studies and on geophysical and statistical criteria. The kriging acts as a low-pass smoothing filter for the anomalous model parameters (velocities), but is not a substitute for an adequate filtering of the outliers before the inversion. This methodology opens the possibility of considering the inverse problem variables as stochastic processes, an important feature in cases where the tomogram is to be used as a tool of assessment to quantify the rock heterogeneities.     

Landscape evolution and geodynamic controls in the Gulf of Cadiz (Huelva coast, SW Spain) during the Late Quaternary

The coastal evolution of the El Abalario area (Huelva, southern Spain) during the Late Pleistocene and Holocene is reinterpreted after a refinement of the available geochronology by means of optically stimulated luminescence (OSL) dating. New data come from the analysis of soft sediment deformation, palaeosols, geomorphological mapping, and published seismic surveys on the onshore and offshore Gulf of Cadiz.The present structure of El Abalario dome resulted from the complex interaction of littoral-catchment processes and sea-level changes upon an emergent coastal plain, conditioned by the upwarping of the underlying Pliocene–Pleistocene prograding deltaic sequence. Upwarping is probably related to escape of over-pressurized fluids, accompanied by dewatering, prior to (?) and during OIS (Oxygen Isotopic Stage) 5. Continued upwarping produced the large NW–SE gravitational fault of Torre del Loro (TLF) in the southwestern flank of the dome, roughly parallel to the present coastline during OIS 5–OIS 4. The resulting escarpment favoured the accumulation of aeolian sand dunes (units U1, U2, and U3) from OIS 5 to early OIS 1. Unit U1 (OIS 5) ends upwards in a supersurface with a thick weathering profile that suggests moist and temperate climatic conditions. Unit U2 accumulated mainly during OIS 4 and OIS 3 with prevailing W/E winds. The supersurface between U2 and U3 records a part of OIS 2, with relative low sea level. Sedimentation of unit U3 took place during the Last Deglaciation (radiocarbon and OSL ages) with prevailing W/SW winds, under a temperate moist climate, that became more arid towards the top (Holocene). A major supersurface with an iron crust-like layer (SsFe) developed during the Holocene Climatic Optimum (OIS 1) under wetter and more temperate conditions than before, fossilizing the TLF. The supersurface is covered by younger aeolian dunes (U4, U5, U6, and U7) transported by W–SW winds since the Late Neolithic–Chalcolithic cultural period (5.0 ky cal BP).     

Seasonal fluctuations in the plankton community in a hypersaline temporary lake (Honda, southern Spain)

Honda saline lake is located in an endorheic basin in the south of Spain. The lake is very shallow, with frequent seasonal drought and a high degree of unpredictability. It was sampled monthly during a relatively dry year (1994–1995, 5 months permanence). To establish a relationship between environmental variables (temperature, depth, salinity and conductivity), variables related to biological activity (organic matter, total solids suspension, and pH) and the planktonic community in the sampled months, various uni-and miltivariate statistical methods were carried out.Dunaliella salina, D. viridis, and ciliates sp. 2 is the principal species group used to average out the dissimilarity between the samples. Muttivariate analysis showed that salinity (as TDS), conductivity and pH made major and significant contributions to the explanation of the variance in the sample data.     

A rapid x-ray fluorescence procedure applicable to exploration geochemistry

A rapid X-ray fluorescence method is described for the analysis of all elements heavier than iron. It is based upon the measurement of a peak and background, while primary scattered radiation is used to correct or compensate for matrix effects. About 15 analyses per man hour can be made on individual samples for such elements as Th, Nb, Ta and W, which are normally difficult to determine by other techniques. Lower limits of detection of about 50 ppm are routinely obtained, and even lower limits of detection (e.g., 20 ppm) can be obtained should these be necessary by increasing the counting time (from 20 to 40 seconds).     

An electoral geography of Western Europe

The European Parliament elections give the opportunity to map voting behaviour in Western Europe. The main methodological difficulty is related to the classification of the parties. The cleavage theory is not a sufficient basis for an operational typology. The left-right axis remains an important basis for a classification. We have discriminated three groups of parties (the left, including the ecologists; the moderate centre-right and classical right; a growing populist reactionary right and the extreme-right, with a different geographical pattern). Beyond those families, the regionalist parties can also be isolated. The green voting pattern is more specific to the central regions and not linked to that of the traditional left, which is related to the traditions of the workers' movement or more specific to the peripheral regions. In general, the metropolitan regions vote more to the left than the surrounding regions, today more and more often on the basis of an intellectual voting pattern, including some well to-do urban and periurban districts. The centre-right and classical right voting pattern designate two main spaces: a conservative mid-European area, with a strong Christian-democracy in the Catholic countries with a quite recent State building (however recently collapsed in Italy), and rural peripheral spaces, mainly those dominated for a long time by small familial rural enterprises and/or by strong and conservative religious practices. At the European scale, the new populist reactionary right is stronger in the `central' regions than the traditional extreme right, even if the latter is also present in some central deprived urban and old industrial districts.     

Coastal lateral spreading in the world heritage site of the Tramuntana Range (Majorca,Spain). The use of PSInSAR monitoring to identify vulnerability

The Bàlitx area is located on the steep coastal side of the Tramuntana Range (Majorca), a mountainous region which was declared a World Heritage Site by UNESCO in 2011 in the cultural landscape category. The Bàlitx site was occupied by farming areas with dry stone constructions and water storing systems of both Roman and Islamic origin. The coastal landscape is characterised by a large fault escarpment of up to 260 m in height. Lateral spreading processes are favoured by local stratigraphy and tectonics in an energetic coastal dynamics scenario. Block spreading morphologies are identified along the escarpment, with large, rocky blocks of volumes up to 60?×?10³ m³ moving very slowly until their collapse. Consequently, a thick and highly karstified breccia deposit is accumulated at the base of the scarp. The lowest, oldest breccia outcrop has been dated (Th/U), and an age of 82.5?±?5.6 kyr was obtained, reflecting the time span this process has been active. Additionally, numerous geomorphological slope features are identified in the area: landslides, rockfalls, and, more specifically, long and deep cracks in the hanging wall block of the fault, which also reveal active lateral spreading processes. Coastal dynamics have been investigated by interpreting offshore geophysical studies, bathymetry data and borehole information to determine the role of wave energy in the stability of the slope. Additionally, 14 SAR images from the ALOS PALSAR satellite have been exploited for the present work, covering a period spanning from 2007 to 2010, an anomalous rainy period in the region. Images were processed using the Persistent Scattered Interferometry (PSI) technique. PSInSAR results reveal that the rate of movement for the Bàlitx lateral spreading is extremely low (??5.2 mm/year on average), but major activity has been detected in the NE sector, where velocity rates can reach values of up to ??16 mm/year Coastal dynamics in the area can explain this, as a small island generates wave refraction and reflection determining more intense erosive processes in the NE part, which lead to a greater destabilising effect on the slopes. A simple vulnerability approach has been developed to take the elements of cultural heritage into account. Vulnerability increases from SW to NE, in accordance with landslide activity. The Bàlitx case study could provide a testimony to the effects of mass movements and coastal dynamics in an exceptional example of Mediterranean agricultural landscape.     

Constraining magma sources using primitive olivine-hosted melt inclusions from Puñalica and Sangay volcanoes (Ecuador)

Constraining arc magma sources at continental arc settings is a delicate task, because chemical signatures from crustal processes obscure the slab and mantle signatures. Here, we present major, trace, and volatile element compositions of olivine-hosted melt inclusions (Fo_82–89) selected from the most primitive lavas (Mg# >?60) from two Ecuadorian volcanoes (Puñalica and Sangay) situated at the southern termination of the Andean Northern Volcanic Zone. Melt inclusions (MI) from Puñalica are nepheline normative and have basaltic-to-basaltic-andesite compositions (45–56 wt% SiO₂) similar to peridotite-derived melts. Sangay MI is also nepheline normative, with high CaO (up to 16 wt% and CaO/Al₂O₃?<?1) and low silica contents (41.9–44.5 wt%) pointing out an amphibole-bearing clinopyroxenite source. Both volcanoes display volatile-rich compositions (up to 6100 ppm Cl, 2200 ppm F, and 6700 ppm S). These MI cannot be related to their host lavas by fractional crystallization, implying that they represent true primitive liquids. The source of Puñalica MI was metasomatized by slab-derived melts that imprints its low Ba/Th, Sr/Th, and high Th/La (average values of 66, 129, and 0.22, respectively). On the contrary, the slab component added to the source of Sangay MI has a higher Ba/Th, Sr/Th, and low Th/La (average values of 261, 517, and 0.11, respectively) which could suggest a relative contribution of aqueous fluids. This dichotomy is related to the presence of the Grijalva Fracture Zone that separates a younger and hotter oceanic crust to the north (below Puñalica) from a colder and older oceanic crust to the south (below Sangay).     

An elasto-visco-plastic model using the finite element method for crustal and lithospheric deformation

A novel numerical model based on solid deformation is presented in this paper. This thermo-mechanical model can simulate the tectonic evolution of crust and (lithospheric and asthenospheric) mantle under different conditions. Our implementation uses the finite element method (FEM) in order to solve the equations. As a Lagrangian approach is employed, remeshing techniques are implemented to avoid distortion problems when a certain deformation threshold is reached. The translation of the state between the old and new mesh is achieved by means of the information stored on Lagrangian particles, which minimizes the diffusion. The model is able to represent elastic, viscous and plastic behaviour inside the studied domain. Three types of creep mechanism (diffusion, dislocation and Peierls) are included. Two different quadrilateral isoparametric elements were implemented and can be employed to perform the calculations. The first one is an element with 4 nodes, selective reduced integration and a stabilization operator to diminish hourglass modes, which reduces the computational time needed. The second one has 8 nodes located in standard positions, uses full integration scheme and has no hourglass modes as it satisfies the Inf-Sup condition. Several test cases with known solutions were run to validate the different aspects of the implementation.