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The fine sand fraction (50–250 μm) of Mediterranean soils from southern Spain provides valuable information on soil genesis and the origin of their parent materials. This study considers the whole fine sand and heavy fine sand (ρ > 2.82 g cm−3) of Luvisols, Calcisols and Fluvisols, which form a chronosequence (ages from 600 to 0.3 ka) of the River Guadalquivir terrace system. Advanced techniques (X‐ray diffraction, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, variable pressure scanning electron microscope with an energy dispersive X‐ray spectroscopy system and Raman analysis) were employed. Inheritance is the principal pedogenic process. The whole fine sand consisted of carbonates (calcite and dolomite), tectosilicates (quartz, K‐feldspar and plagioclases), phyllosilicates (illite/moscovite, biotite, Na‐mica, chlorite, kaolinite, interstratified vermiculite‐chlorite, vermiculite‐illite and smectite‐illite) and iron oxides (goethite and haematite). The minor minerals (rutile, anatase, ilmenite, zircon, staurolite, monazite, barite, apatite, andalusite, garnet and titanite) are concentrated, also through inheritance, in the heavy fine sand. However, there is also substantiated evidence for neoformation of rutile in these soils, never reported previously. In addition, we report that (a) the geochemical indices calculated in fine sand (SiO2/CaO, Chemical Index of Weathering (CIW), Weathering Index of Parker (WIP), Weathering Index (WI), Base Depletion Index (BDI), Weathering Ratio (WR) and Sr/Zr) are closely related to soil age, allowing chronofunctions to be established, and (b) geochemical indices provide information on the origin of soils and permit the establishment of a "critical point" corresponding to "time zero;" that is, the start of pedogenic alteration of the parent material. Highlights: Mineralogy and geochemistry inform on the provenance of the fine sandRutile is neoformed in the fine sand and co‐exists with the polymorph anataseThe properties of the fine sand including geochemical indexes fit chronofunctionsGeochemical indices determine a "critical point" related to the start of weathering [ABSTRACT FROM AUTHOR]

Currently, there are some initiatives aimed at transforming agriculture from being a source to a sink of greenhouse gases, mainly by encouraging combination of management practices that drive nature-based climate processes (NbCS) resulting in an increase in the stocks of soil and biomass organic carbon. Olive grove cultivation represents a key socio-economic and environmental asset for Mediterranean rural regions. Being a woody crop planted in an orchard fashion, the potential for organic carbon accumulation in the biomass and the soil is very high. In this study, farm, trees and soil carbon balances were analysed in 12 pairs of olive groves located in Southern Spain with different tree densities, age, varieties and irrigation regimens. One from each pair of the olive groves has applied (> 8 years) a combination of management practices that promote NbCS resulting in an increase in the entry of carbon, whereas the other comparable nearby olive grove has not implemented management practices that promote NbCS or C entries (non-NbCS). C balance at the farm level was mainly neutral or positive and averaged + 1.20 Mg C ha−1 y−1. However, C balance in the NbCS olive groves was 5 times higher than that of the non-NbCS. The mean soil C balances were negative (−0.18 Mg C ha−1 y−1; losing soil organic C) in the non-NbCS and positive (+1.48 Mg C ha−1y−1) in the NbCS olive groves thanks to the increase in the carbon entries due to the management practices which boost NbCS. This study highlights the important contribution of olive farming in mitigating climate change, which in turn would be an economic incentive for olive growers. Nonetheless, there is a high potential for improvement by implementing management practices which enhance nature-based processes such as the cultivation of temporary spontaneous cover crops and the application of shredded tree pruning and composted olive mill pomace and/or manure to the soil. • C balance at farm level was positive in 21 out of 24 olive farms. • In some farms, the losses of SOC were compensated by the C gains in the trees. • C balance in NbCS olive groves was 5 times higher than these of the non-NbCS. • There was a clear positive relationship between soil C balance and the managed C inputs. [ABSTRACT FROM AUTHOR]

• Better growth: F. pulverulenta > A. prostrata > P. coronopus. • Increase in Na+ and Cl−, and decrease of K+ in plants with saline excretion. • Greater increase of metabolite concentrations in the most tolerant plants. • A common signaling response (phenols and polyamines) in three halophytes. Soil analyses of three saltmarshes in Jaén province (southern Spain) indicated Sodic Solonchack type for Don Benito saltmarsh, and Sodic Calcixerepts for Barranco Hondo and Brujuelo saltmarshes. Three halophytes (Frankenia pulverulenta , Atriplex prostrata , and Plantago coronopus) from these saltmarshes were submitted to long (21 days) and gradual (0, 100, 200, and 300 mM NaCl) salinity stress, under hydroponic culture. The results of fresh mass, dry mass, root:shoot ratio, leaf water content, ion content, proline, total phenols, and polyamines (putrescine, spermidine, spermine and cadaverine) were examined to investigate the species' responses to saline stress. Maximum biomass production and leaf water content was found between 100 and 200 mM NaCl in F. pulverulenta and at 100 mM NaCl in A. prostrata , while a decrease of these parameters was registered in P. coronopus as the salt concentration and salt-exposure time increased. In leaves, Na+ and Cl− accumulation increased with salt concomitant with a reduction of K+ in plants with salt excretion mechanisms (F. pulverulenta and A. prostrata), while high levels of ions were found with and without salt in P. coronopus. For osmotic adjustment, proline content proved important in F. pulverulenta and A. prostrata , while in P. coronopus this osmolyte decreased with salt, while phenols and polyamines increased in all three species. The highest levels in (Spermidine + Spermine): Putrescine ratio was related to the more salt-tolerant species. These results appear to indicate various adaptation responses to salinity. Rising levels of proline, phenols, and polyamines were related to better growth, which could contribute to different degree of tolerance and distribution of these species in saltmarshes. [ABSTRACT FROM AUTHOR]