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Abstract: In the Mediterranean region, the long history of cultivation is associated with significant changes in the original landscape. Agricultural intensification and subsequent land abandonment and reforestation have significantly affected the hydrological behaviour and connectivity patterns of hydrological systems. Thus, information on the spatial distribution of land use/cover is essential for monitoring the runoff response to interpret catchment hydrology. A medium‐sized catchment of the central part of the Ebro Basin (NE Spain), representative of Mediterranean mountain agroecosystems, was selected to assess the effect of land use/cover changes during the last few decades on the hydrological network of the catchment. To this end, a topography‐based index, the ‘index of connectivity’, was applied to assess the effects of land use changes from 1957 to 2010. The sediment connectivity was estimated by using a geomorphometric approach to simulate how connectivity changes due to the different land covers. To improve this index, we used a combination of C‐factor, rugosity index and the novel application of a total aerial biomass equation over pine‐reforested areas as a weighting factor. A high‐resolution (1 × 1 m) digital elevation model was created by filtering and applying a multiscale curvature classification algorithm. The connectivity values show a decrease directly related to ~71% decrease of agricultural land. Understanding landscape patterns, changes and interactions of human activities is essential for land management in Mediterranean agroecosystems. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In Mediterranean mountainous environments, the removal of natural vegetation for developing agriculture increased the surface areas prone to erosion in the past centuries. In Southern Pre‐Pyrenees, the process was inverted during the middle of the 20th century. This work aims to assess how land use changes after widespread land abandonment affect soil redistribution. For this purpose, 137Cs was used in a 23 km2 catchment that was mostly cultivated at the beginning of the past century. After land abandonment, 16.5% of croplands persisted but afforestation and natural revegetation occupy 83.5% of the catchment area. 137Cs massic activity and related soil properties—stoniness, grain size, and organic matter contents—were analysed in 98 bulk core samples. Physiographic characteristics—slope, altitude, and solar radiation—at the sampling points were determined by using Geographic Information Systems. Soil erosion and deposition rates were derived from 137Cs measurements after applying conversion models and were spatially interpolated to estimate the amount of net soil loss. In cropland soils, mean erosion (62.6 Mg ha−1 yr−1) and deposition rates (55.2 Mg ha−1 yr−1) were significantly higher than in the other land uses. The lowest mean erosion rates (2.4 Mg ha−1 yr−1) were found in natural forests and the lowest mean deposition (2.6 Mg ha−1 yr−1) in pine afforestation evidencing the soil stabilization achieved in the last decades due to revegetation. A sediment budget with the interpolated rates, result in a specific sediment yield of 4.15 Mg ha−1 yr−1. These results outline the impact of land use changes on soil redistribution in fragile mountain agroecosystems. [ABSTRACT FROM AUTHOR]

Land management in agricultural lands has important effects on soil organic carbon (SOC) dynamics. These effects are particularly relevant in the Mediterranean region, where soils are fragile and prone to erosion. Increasing interest of modelling to simulate SOC dynamics and the significance of soil erosion on SOC redistribution have been linked to the development of some recent models. In this study, the SPEROS-C model was implemented in a 1.6-ha cereal field for a 150-year period covering 100 years of minimum tillage by animal traction, 35 years of conventional tillage followed by 15 years of reduced tillage by chisel to evaluate the effects of changes in land management on SOC stocks and lateral carbon fluxes in a Mediterranean agroecosystem. The spatial patterns of measured and simulated SOC stocks were in good agreement, and their spatial variability appeared to be closely linked to soil redistribution. Changes in the magnitude of lateral SOC fluxes differed between land management showing that during the conventional tillage period the carbon losses is slightly higher (0.06 g C m−2 yr−1) compared to the period of reduced till using chisel (0.04 g C m−2 yr−1). Although the results showed that the SPEROS-C model is a potential tool to evaluate erosion induced carbon fluxes and assess the relative contribution of different land management on SOC stocks in Mediterranean agroecosystems, the model was not able to fully represent the observed SOC stocks. Further research (e.g. input parameters) and model development will be needed to achieve more accurate results. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Exceptional rainfall events cause significant losses of soil, although few studies have addressed the validation of model predictions at field scale during severe erosive episodes. In this study, we evaluate the predictive ability of the enhanced Soil Erosion and Redistribution Tool ( SERT-2014) model for mapping and quantifying soil erosion during the exceptional rainfall event (~235 mm) that affected the Central Spanish Pyrenees in October 2012. The capacity of the simulation model is evaluated in a fallow cereal field (1.9 ha) at a high spatial scale (1 × 1 m). Validation was performed with field-quantified rates of soil loss in the rills and ephemeral gullies and also with a detailed map of soil redistribution. The SERT-2014 model was run for the six rainfall sub-events that made up the exceptional event, simulating the different hydrological responses of soils with maximum runoff depths ranging between 40 and 1017 mm. Predicted average and maximum soil erosion was 11 and 117 Mg ha−1 event−1, respectively. Total soil loss and sediment yield to the La Reina gully amounted to 16.3 and 9.0 Mg event−1. These rates are in agreement with field estimations of soil loss of 20.0 Mg event−1. Most soil loss (86%) occurred during the first sub-event. Although soil accumulation was overestimated in the first sub-event because of the large amount of detached soil, the enhanced SERT-2014 model successfully predicted the different spatial patterns and values of soil redistribution for each sub-event. Further research should focus on stream transport capacity. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The main sources of magnetic minerals in soils unaffected by anthropogenic pollution are iron oxides and hydroxides derived from parent materials through soil formation processes. Soil magnetic minerals can be used as indicators of environmental factors including soil forming processes, degree of pedogenesis, weathering processes and biological activities. In this study measurements of magnetic susceptibility are used to detect the presence and the concentration of soil magnetic minerals in topsoil and bulk samples in a small cultivated field, which forms a hydrological unit that can be considered to be representative of the rainfed agroecosystems of Mediterranean mountain environments.Additional magnetic studies such as isothermal remanent magnetization (IRM), anhysteretic remanent magnetization (ARM) and thermomagnetic measurements are used to identify and characterize the magnetic mineralogy of soil minerals. The objectives were to analyse the spatial variability of the magnetic parameters to assess whether topographic factors, soil redistribution processes, and soil properties such as soil texture, organic matter and carbonate contents analysed in this study, are related to the spatial distribution pattern of magnetic properties. The medians of mass specific magnetic susceptibility at low frequency (χlf) were 36.0 and 31.1 × 10−8 m3 kg−1 in bulk and topsoil samples respectively. High correlation coefficients were found between the χlf in topsoil and bulk core samples (r = 0.951, p < 0.01). In addition, volumetric magnetic susceptibility was measured in situ in the field (κis) and values varied from 13.3 to 64.0 × 10−5 SI. High correlation coefficients were found between χlf in topsoil measured in the laboratory and volumetric magnetic susceptibility field measurements (r = 0.894, p < 0.01). The results obtained from magnetic studies such as IRM, ARM and thermomagnetic measurements show the presence of magnetite, which is the predominant magnetic carrier, and hematite. The predominance of superparamagnetic minerals in upper soil layers suggests enrichment in pedogenic minerals. The finer soil particles, the organic matter content and the magnetic susceptibility values are statistically correlated and their spatial variability is related to similar physical processes. Runoff redistributes soil components including magnetic minerals and exports fine particles out the field. This research contributed to further knowledge on the application of soil magnetic properties to derive useful information on soil processes in Mediterranean cultivated soils. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a useful indicator of soil fertility that plays an important role in improving soil quality, increasing agronomic productivity and maintaining sustainability of agricultural systems. The use of hyperspectral data for SOC estimation offers a fast, cost-effective, and non-destructive alternative to conventional soil analyses. Spectral data analysis with multivariate statistical methods has been already successfully used to transfer soil reflectance data on quantitative estimation of SOC content. The spectral sensor type and calibration, and the data acquisition conditions are determinants of the quality and accuracy of the hyperspectral data. Therefore, our study aims to test the capability of the Vis-NIR-SWIR spectral information for the quantitative prediction of organic carbon content in Mediterranean soils by comparing laboratory-based spectroscopy and spectral data acquired in field conditions. We also test the effect of changes in solar illumination on the soil spectral reflectance by comparing soil spectral data under field conditions in different sky conditions.In 2017, soil samples were collected in a Mediterranean agricultural mountain landscape (NE Spain) where the main land uses are cropland, Mediterranean natural forest and scrubland and pine afforestation. We selected a dataset (n=73) that includes a wide range of SOC content from 2 to 71 g kg-1. Laboratory-based spectral data of the soil samples were acquired using an ASD FieldSpec 3 portable spectroradiometer (350 – 2500 nm wavelength range) in a dark room to avoid interference from stray light. An average value of 4 spectral measurements for each sample was used as the final spectral reflectance. In addition, multispectral data were acquired in field conditions with a RedEdge-M narrow-band multispectral camera. After spectral measurements, the SOC content (g kg-1) of all soil samples was measured at 550°C by dry combustion using a LECO RC-612 multiphase carbon analyser. These laboratory reference SOC measurements were coupled with the laboratory and field derived spectral measurements to explore the correlations between soil spectra and SOC. Results of partial least squares regression (PLSR) modelling of spectral data show that the tested multispectral narrow-bands were useful for SOC prediction with a satisfactory level of accuracy (root mean square error, RMSE = 1.15, ratio of performance to deviation, RPD = 1.44, R2 = 0.61) The spectral data provided by the tested multispectral camera can be successfully employed for SOC prediction in field conditions, providing an efficient method for fast acquisition of data also in the spatial domain, especially in the perspective of UAV applications. [ABSTRACT FROM AUTHOR]

Soil tillage and erosion promote the break up of soil structure and loss of carbon. Soilstructure is one of the main factors controlling the ability of soil to support plant growth, themovement of water and the cycling of carbon and nutrients. Therefore soil aggregation is animportant soil property for farmers. Soil aggregation affects soil organic carbon stabilizationand the ability of soils to resist erosion. Soil aggregate size distribution and stability representtwo indicators of soil physical quality that may change in response to soil redistributionprocesses.This study was performed to evaluate soil structural stability and aggregate-associated SOCdynamics in a Mediterranean mountain agroecosystem (NE Spain). The fieldwork wasconducted in 2017, and included the collection of topsoil samples (0-20 cm) fromcroplands after crop harvest at two contrasting slope positions representing eroded anddepositional sites. The main crops were winter cereals and soils with a mean value ofpH 8.5 and EC 0.11 dS m-1 and a silt loam texture are developed on sedimentaryrocks. Aggregate size separation and soil stability assessments were carried out onsoil replicates using a wet sieving method from Six et al. (2000). A total of 80 gair-dried soil samples (8 mm sieved) were fractionated through three sieves (2000, 250and 53 μm) into four aggregate-size classes: large macroaggregates (2000-8000μm), small macroaggregates (250–2000 μm), microaggregates (53-250 μm) andsilt-plus clay-sized particles (&#x003C;53 μm). Sand correction was performed for eachaggregate-size class. SOC contents in topsoils and in each aggregate fractions weremeasured by the dry combustion method and soil aggregate stability was expressedby the mean weight diameter (MWD, mm) and geometric mean diameter (GMD,mm).Different physical-chemical properties in topsoils were observed from the upper to thelower part of the slope. Large differences in SOC concentration and soil aggregationin topsoils between the eroded (mean SOC 2.4 g kg-1) and depositional (meanSOC 5.0 g kg-1) sites were found. The results showed an increase in the weightproportion (%) of all the aggregate size fractions at the lower part of the slope exceptfor the silt-plus clay-sized particles. MWD and MGD mean values were lower(0.40 mm and 0.39 mm) at the upper part of the slope compared to the lower part(0.98 mm and 0.53 mm). Topsoils at the depositional site had a better aggregatestructure and higher aggregate stability than those at the eroded site. This workcontributes to evaluate the effect of soil redistribution processes, responsible for themobilization and deposition of soil aggregates and associated soil organic carbon, on soilstructural stability which is crucial for maintaining soil productivity of Mediterraneanagroecosystems. Acknowledgements: This research was supported by the &#x0022;MOVE-IN Louvain&#x0022; IncomingPost-doctoral Fellowship (L.Quijano as a beneficiary), co-funded by the Marie Curie Actionsof the European Commission (MSCA-COFUND). [ABSTRACT FROM AUTHOR]

The present dominant trend of retreating and shrinking glaciers is leading to the formation of new soil in proglacial zones. The Cordillera Blanca located in the Peruvian Andes includes the Lake Parón catchment known for the Artesonraju Glacier and its rapid retreat, forming the largest proglacial lake in the region. This work aims to gain knowledge of soil and vegetation development on the most representative proglacial landforms existing in the Parón catchment. Previous research in proglacial environments suggests that soil properties might indicate different ages of ice retreat besides the normalised difference vegetation index (NDVI), which is known to be a powerful tool for assessing vegetation development. In the area surrounding Lake Parón up to the glacier tongue, an altitudinal transect (4200-4700 m a.s.l.) was established for sampling topsoils. A total of 40 surface soil samples (0-3 cm) were collected from the main glacial landforms, moraines, colluvium, glacio-fluvial terraces and alluvial fans, developed after different stages of glacier retreat. Soil organic carbon (SOC) and SOC fractions (active and stable), total nitrogen (TN) and 137 Cs were analysed. A multitemporal analysis of NDVI was performed to assess the vegetation dynamics in the Parón catchment and over the different glacial landforms over time (1987-2018). The NDVI increase in recent decades indicates an expansion of vegetation cover and density. We compared NDVI values with the SOC and TN content to assess the relationships with vegetation growth in mountain soils. NDVI and the distribution of SOC and TN content show a positive correlation between vegetation evolution and the enrichment in soil nutrients that are more abundant in older moraines in coincidence with highest NDVI. These results outline the effect of shrinking mountain glaciers on generating new soils in parallel with the growth of vegetation., (Copyright © 2018 Elsevier B.V. All rights reserved.)