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Land use changes due to natural and human-related factors, which include wildfires and crop abandonment, are among the most important drivers of soil degradation and demand regular monitoring. Proximal soil sensing in visible–near infrared–shortwave infrared spectral regions could offer a solution. However, to become operational, optimal combination of data and technique has to be defined. Thus, the purpose of this study was (a) to predict the soil organic matter (SOM) content and soil texture in areas of wildfire burns and crop abandonment in Aragón Province, Northern Spain, from their laboratory reflectance spectra using novel correlated components regression with a step-down variable selection algorithm (CCR-SD) and (b) to compare the CCR-SD and the partial least squares regression (PLSR) methods. The results obtained by the tested methods were similar. CCR-SD models showed high predictive capacity with coefficients of determination (R2) in the range of 0.80–0.86 and 0.70–0.87 for calibration and validation data sets, respectively, and the highest R2 value was attained in the SOM estimation. Moreover, the CCR-SD models stand out for the superior accuracy–parsimony relationship: the number of predictors varied from 16 (silt models) to 49 (SOM models). On average, the CCR-SD calibrations needed less than a half of the predictors employed in PLSR models. This research confirmed that CCR-SD can be used for monitoring SOM content and texture of soils from visible–near infrared–shortwave infrared spectra in the study area and, probably, in other areas of land use/land cover change and that CCR-SD can create highly parsimonious models that achieve results comparable with the commonly used PLSR method.

Vegetation expansion following farmland abandonment is a complex process that depends on multiple natural and human-induced factors, resulting in differences in the evolution of land cover on former cultivated fields, with various environmental implications. To assess the complexity of the hydrogeomorphological consequences of farmland abandonment, the Instituto Pirenaico de Ecología (CSIC) and the University of La Rioja monitored three small catchments, representative of different post land abandonment scenarios, in the Pyrenees and Iberian Range respectively. In the Pyrenees, a fourth small catchment, covered by natural forest, was monitored as a reference for an undisturbed environment. This study describes the evolution of land use in the abandoned catchments and examines its implications on catchment hydrological connectivity. It also analyses the hydrological responses of the three abandoned scenarios to similar rainfall events, and compares them to that of natural forested areas. Vegetation tended to increase in the three catchments, but there were important differences in the characteristics of the current land cover. Arnás, the catchment left to a process of natural revegetation, contained a mosaic of shrubs (64%) and forest (27%) at different stages of succession, largely conditioned by the topography and soil properties. Araguás_afforestation was extensively afforested in the 1960s, with 75% of this catchment currently covered by forest, most of it planted artificially. In Munilla, occupied by terraced fields, vegetation recovery was partly restrained by the introduction of cattle, and 80% of the catchment was covered by sparse shrubs. Land abandonment resulted in a general reduction in computed hydrological connectivity in the three studied catchments, except in localized areas close to the main channel, new forest roads and trails, and upstream of terrace wall collapses, all areas of increased hydrological connectivity. The decrease in hydrological connectivity was much lower in Munilla, characterized by an absence of dense vegetation and still dominated by a terraced topography. The hydrological responses of the catchments to similar rainfall events differed significantly, showing the influence of not only vegetation cover but of the properties of soil remaining after previous agricultural activities. Significant storm-flow discharge was observed in Arnás, even under dry conditions, with high peakflows and fast responses. Lower streamflow response was observed in Araguás_Afforestation under dry conditions; however, once the soils were wet the hydrological response was notable and was characterized by high peakflow. The response under afforested trees differed greatly from that of a catchment covered by natural forest, with the latter characterized by gentler hydrographs. The hydrological response in Munilla was the lowest, with long response times and recessions, associated with the thick soils of the terraced fields. These results demonstrated the large variability of post land abandonment scenarios and associated hydrological implications, and highlighted the need to consider these differences to reduce future uncertainties in forecasting water resources and soil conservation.

The effects of afforestation on water resources are still controversial. The aim of this paper is to (i) analyze the hydrological response of an afforested area in the Central Pyrenees, and (ii) compare the hydrological response of an afforested area with the response observed in a natural undisturbed forest. The Araguás catchment was cultivated until the 1950s, and then afforested with pines in an effort to control the active degradation processes. The hydrological response was variable and complex, because the discharge was generated by a combination of distinct runoff processes. The hydrological response showed that: (i) afforestation produced moderate peak discharges, stormflows and recession limbs, and long rising limbs; (ii) no one single variable was able to explain the hydrological response: rainfall volume and intensity did not explain the hydrological response and antecedent rainfall and initial discharge (indicating antecedent moisture conditions) did play an important role, (iii) seasonal differences were observed suggesting different runoff generating processes, and (iv) the effect of forest cover on peak discharges became less important as the size of the hydrological event increased. The stormflow coefficient showed a clear seasonal pattern with an alternation between a wet period, when the catchment was hydrologically responsive, and a dry summer period when the catchment rarely responded to any event, and two transitional periods (wetting and drying). Compared to a natural forest, the afforested area recorded greater flows and peak discharges, faster response times and shorter recession limbs. Afforestation reduces the water yield and the number of floods compared to non-vegetated areas and abandoned lands.

During the 20th century, Euro-Mediterranean mountains underwent a process of marginalization, with high rates of emigration, land abandonment, reduction of livestock census and poor use of pasture and forest products. Marginalization, with the abandonment of most of the fields and pastures, encouraged secondary succession processes that favored the expansion of shrubs and forests. Simultaneously, the administration encouraged the reforestation of large areas for economic purposes (the increase of wood and paper pulp production) and environmental objectives (the regulation of floods and prevention of soil erosion and degra- dation). As a result of these changes, Mediterranean mountain landscapes have been simplified and homogenized, fragmentation has been reduced and many of their cultural values are being degraded, a trend that also involves the loss of local knowledge on sustainable land management. The expansion of vegetation shows other negative effects, including an increase of fire risk, a reduction in water availability, the concentration of sediment sources in ancient agricultural terraces (which maintain the most fertile and deepest soils), loss of biodiversity and problems for the economic sustainability of the mountain, due to pasture degradation, and the loss of an attractive landscape. On the other hand, we must take into account that the impacts of land use changes in mountain areas occur not only at a local scale, but also at regional and global scales, as mountain ecosystems provide a range of goods and services to the society. The aim of this study is to investigate the diversity of opinions that people linked to Camero Viejo (Iberian Range) present about the major environmental changes since the mid-twentieth century: (i) vegetation cover dynamics, (ii) soil erosion, (iii) water yield and quality, (iv) fire risk, and (v) changes in wildlife and landscape. This perception will be related to current changes, quantified from land cover and land uses maps, information taken in the administration, and literature of the study area. The final objective is to find out which social groups have a closer or unrealistic perception; in that way, decision-makers could obtain more information to develop and implement new public policies.

A small catchment affected by agricultural practices in the past, then progressively abandoned and naturally re-vegetated was monitored in the central Spanish Pyrenees. The results obtained over a 9-year period revealed the complexity of its hydrological and geomorphological behaviour. Several runoff generation processes can occur at the same time and in different parts of the catchment, depending on the water reserves conditions and rainfall characteristics. Sediment response is mainly controlled by the spatial and temporal dynamics of water and sediment contributing areas within the catchment. The sediment output illustrates the complexity of the geomorphic response of mountain environments modified by past farmland activities., Se presenta una síntesis de la investigación realizada en una pequeña cuenca experimental afectada por una intensa actividad agraria en el pasado y sujeta a un proceso de revegetación natural en la actualidad en el Pirineo Central. Los principales resultados obtenidos demuestran su complejo comportamiento hidrogeomorfológico. El análisis de la información hidrológica sugiere que diferentes procesos dominantes de generación de escorrentía pueden ocurrir de manera simultánea en diferentes áreas de la cuenca, en función del estado de humedad de la misma y de las características de la precipitación. La respuesta sedimentológica está principalmente controlada por la dinámica espacio-temporal de las áreas fuente de escorrentía y de sedimento. La exportación de sedimento ilustra la complejidad de la respuesta geomorfológica en los ambientes de montaña afectados por actividades agrarias en el pasado.

The main landscape feature in the Pyrenean middle mountain is the presence of hillslopes occupies by old cultivated fields already abandoned, affected by different stages of plant colonization. By means of experimental plots, this paper studies runoff generation and sediment yield in two types of abandoned fields: (i) sloping fields previously cultivated with cereal and frequently fertilized; and (ii) fields corresponding to shifting agriculture, with scarce conservation measures. The results obtained were compared to a dense shrub cover plot. The abandoned plots yield much more water and sediment than the dense shrub cover, which shows a lower variability in the hydromorphological response. The progressive plant colonization of the two abandoned plots favoured the occurrence of a negative trend in runoff and erosion. This paper also demonstrated that the shifting agriculture fields yield more water and erosion than sloping fields, because of difficulties for plant succession. El principal rasgo paisajístico de la montaña media pirenaica es la presencia de extensas laderas ocupadas por antiguos campos de cultivo ya abandonados, en distintas fases de colonización vegetal. A partir de parcelas experimentales, este trabajo estudia la generación de escorrentía y la producción de sedimento en dos tipos de campos abandonados: (i) campos en pendiente previamente cultivados con cereal y abonados frecuentemente, y (ii) campos correspondientes a agricultura nómada, con escasas medidas de conservación. Los resultados se compararon con una parcela de matorral denso. Se ha comprobado que las dos parcelas abandonadas producen mucha más agua y sedimento que el matorral, que además muestra una menor variabilidad en su respuesta hidromorfológica. La progresiva colonización vegetal de las dos parcelas abandonadas favorece la ocurrencia de una tendencia regresiva en la escorrentía y la erosión. Este trabajo demuestra también que los campos de agricultura nómada producen más agua y erosión debido a las mayores dificultades para que avance la sucesión vegetal.

This paper analyses the stormflow response of the San Salvador forested catchment (0.92 km2) located in the Central Pyrenees, Spain. Using stormflow coefficient and discharge increment, the temporal variability of the rainfallrunoff relationship is analyzed at the event scale from hydrographs observed over a 7-year period. Results show that the storm-flow coefficient has a clear seasonal pattern with an alternance between a wet period, when the catchment is hydrologically responsive, and a dry summer period, when the catchment presents almost no reaction to any rainfall. The relationships of the storm-flow coefficient and discharge increment with several hydrological variables shows similar (but lower) correlations than usually observed in other Mediterranean or temperate catchments and demonstrates that the storm flow response is mainly depending on water table with rainfall depth and base flow as secondary factors. The marked seasonality observed in the San Salvador catchment is most likely accentuated by forest that cover all the catchment, but this deserves further investigations. El análisis de los procesos hidrológicos en zonas forestales es objeto de numerosos estudios, debido a los cambios ambientales que se están produciendo en los últimos años y a los cambios experimentados en los usos del suelo desde las últimas décadas, como resultado del proceso de revegetación. Este trabajo analiza la respuesta hidrológica de la pequeña cuenca forestal de San Salvador (0.92 km2), localizada en el Pirineo Central, España. Se ha analizado la variabilidad de las relaciones precipitación-caudal a escala de evento, durante un periodo de estudio de 7 años, teniendo en cuenta los coeficientes de escorrentía de crecida y el incremento de la descarga. Los resultados muestran que el coeficiente de escorrentía presenta un gran patrón estacional con una alternancia entre periodos húmedos, cuando la cuenca tiene capacidad de responder hidrológicamente, y periodos secos, cuando la cuenca casi no reacciona a ninguna precipitación. La relación entre el coeficiente de escorrentía y el incremento de la descarga con otras variables hidrológicas muestra correlaciones similares (aunque siempre más bajas) que las observadas en otras cuencas mediterráneas y templadas, y demuestra que la escorrentía depende principalmente de la profundidad de la capa freática y del flujo de base como factor secundario. La marcada estacionalidad observada en la cuenca de San Salvador es probablemente más acentuada debido a la densa cubierta forestal, pero este hecho merece futuras investigaciones.

The Inner Depression (Central Pyrenees) presents a great heterogeneity of land uses and vegetation covers. In this context, a hundred of badlands areas are distributed along the ranges of the Depression. This morphologies occurrence has been associated to the combination of different factors: bedrock, climate, deforestation, slope terracing and field crop abandonment. In this way, most of the hydrological basins show a mosaic of contrasted environments: badlands, meadows, meadows with shrubs and reforested slopes. This study presents the analyses of the hydrological response on the Araguás catchment, which is monitored for recording discharges from the most extreme environments: badlands and reforested slopes. The results show great differences on discharge generation, both by runoff generation processes and by its frequency and water volume. Reforested environments decreases flooding and erosion risks, but also generate a big reduction of water resources disposability., La Depresión Interior Altoaragonesa (Pirineo Central) presenta una gran heterogeneidad de usos del suelo y cubiertas vegetales. En este contexto destaca el centenar de morfologías acarcavadas distribuidas a lo largo de los márgenes de la Depresión. La presencia de estas morfologías se ha asociado a la combinación de varios factores: el substrato rocoso, el clima, la deforestación, el aterrazamiento de laderas y el abandono de cultivos. Esto origina que la mayoría de las cuencas hidrológicas presenten un mosaico de ambientes contrastados: cárcavas, prados, prados con matorral y laderas reforestadas. En este estudio se presenta el análisis de la respuesta hidrológica en la cuenca de Araguás, monitorizada para el registro de caudales generados en las situaciones más extremas: cárcavas y laderas reforestadas. Los resultados revelan grandes diferencias en la generación de caudales, tanto por los procesos que intervienen, como por su frecuencia y el volumen de agua generado. Los ambientes reforestados disminuyen el riesgo de avenidas y la erosión, pero también llevan asociada una fuerte reducción en la disponibilidad de los recursos hídricos.