José Arnáez

Marginal Lands and Erosion in Terraced Fields in the Mediterranean Mountains A Case Study in the Camero Viejo (Northwestern Iberian System, Spain)

Abstract Since the 1950s, the Spanish Mediterranean mountains have become a marginal territory, with few inhabitants and limited economic activity. As a consequence, significant land use changes (farmland abandonment, development of extensive cattle rearing, and reforestation) have taken place, resulting in landscape degradation and new hydromorphological processes. In this article, the process and impact of farmland abandonment in the Camero Viejo (northwestern Iberian System) are described. The authors also studied the geomorphological evolution of terraced fields after cultivation was given up. Runoff rates and sediment yield in abandoned and grazed terraces were measured using a rainfall simulator. Results show that the speed and intensity of the hydrological and erosional response increased if plots were grazed intensively. The study demonstrates that new land management systems in the Camero Viejo, in particular extensive cattle grazing, have generated additional source areas of sediments.

Uncertainty assessment in the prediction of extreme rainfall events: an example from the central Spanish Pyrenees

Extreme rainfall events occur frequently in the central Pyrenees, but they are responsible for mass movements and short, very intense erosion periods, accompanied at times by loss of human life and high costs of infrastructure. This paper tries to assess the existence of patterns in the spatial distribution of maximum precipitation. The calculation of return periods of the most intense rainfall demonstrates that in the Pyrenees it exhibits an erratic spatial and temporal distribution and can be extremely localized. In the case of precipitation between 150 and 200 mm in 24 h, some influence from the surrounding relief has been found, but this is not the case for precipitation exceeding 200 mm, characterized by the absence of patterns governing their spatial distribution. Geomorphological approaches are, therefore, the only way for assessing the areas more subject to hydromorphological risks. Copyright

Factors Explaining the Spatial Distribution of Hillslope Debris Flows

Abstract The spatial distribution of 961 debris flows in the Upper Aragón and Gállego valleys (Central Spanish Pyrenees) was analyzed. Most were located in the Flysch Sector (with a colluvium mantle derived from strongly tectonically modified materials), between 1000 and 1400 m above sea level, on 25–35° gradients with sunny exposure. These gradients were either hillslopes covered by frequently burned scrubland, abandoned fields, or reforested land, confirming the influence of land use and disturbed landscapes on the occurrence of debris flows.

Sediment sources in a small, abandoned farmland catchment, central Spanish Pyrenees

Abstract In an abandoned farmland catchment the eroded areas have been mapped in order to locate the possible sediment sources. Besides large, non functional mass movements, three types of processes and geoforms stand out: small debris flows, areas where sheet wash erosion prevails and scars located in the taluses flanking the main ravine. Fieldwork and the first results obtained on sediment transport at the outlet of the catchment suggest that the sediment contributing area, representing less than 1 percent of the basin, is mostly the channel itself and its taluses.

Mid and late Holocene forest fires and deforestation in the subalpine belt of the Iberian range, northern Spain

The conversion of subalpine forests into grasslands for pastoral use is a well-known phenomenon, although for most mountain areas the timing of deforestation has not been determined. The presence of charcoal fragments in soil profiles affected by shallow landsliding enabled us to date the occurrence of fires and the periods of conversion of subalpine forest into grasslands in the Urbión Mountains, Iberian Range, Spain. We found that the treeline in the highest parts of the northwestern massifs of the Iberian Range (the Urbión, Demanda, Neila, and Cebollera massifs) is currently between 1500 and 1600 m a.s.l., probably because of pastoral use of the subalpine belt, whereas in the past it would have reached almost the highest divides (at approximately 2100–2200 m a.s.l.). The radiocarbon dates obtained indicate that the transformation of the subalpine belt occurred during the Late Neolithic, Chalcolithic, Bronze Age, Iron Age, and Middle Ages. Forest clearing was probably moderate during fires prior to the Middle Ages, as the small size of the sheep herds and the local character of the markets only required small clearings, and therefore more limited fires. Thus, it is likely that the forest recovered burnt areas in a few decades; this suggests the management of the forest and grasslands following a slash-and-burn system. During the Middle and Modern Ages deforestation and grassland expansion affected most of the subalpine belt and coincided with the increasing prevalence of transhumance, as occurred in other mountains in the Iberian Peninsula (particularly the Pyrenees). Although the occurrence of shallow landslides following deforestation between the Neolithic and the Roman Period cannot be ruled out, the most extensive shallow landsliding processes would have occurred from the Middle Ages until recent times.

Effects of wheel traffic on runoff and soil erosion in slopes cultivated with vineyards

Mechanization characterizes the vineyards of La Rioja, one of the most important wine regions in Spain. Farming operations (plowing, soil removal, herbicide and pesticide application, harvesting of grapes and its transportation, 115 No 38 (1) pp. 115-130 ISSN 0211-6820 Cuadernos de Investigación Geográfica 2012

EVOLUCIÓN DEL PAISAJE VITÍCOLA EN LA RIOJA (2000-2015): UN ANÁLISIS DEL PAPEL DE LOS PROGRAMAS DE RECONVERSIÓN Y REESTRUCTURACIÓN DEL VIÑEDO

In recent decades the wine landscape of La Rioja has experienced a radical change, connected with wine market dynamics and internal changes in the wine sector (increase in the areas of vineyards managed by big wine companies) as well as the provisions emanating from public policies, especially all those which arose from the Common Market Organization [CMO] in 1999 and 2008, within the Common Agricultural Policy (Regulations 1493/1999 and 479/2008). Recent changes in the vineyard landscape in La Rioja as a consequence of restructuring programmes derived from wine sector CMOs in 1999 and 2008, are analysed in this paper. The results show grubbing-up of vines, the expansion of new plots on irrigated lands, and the increasing presence of vines grown on trellises; changes that bring a natural decline in landscape aesthetics. Such changes, however, are insufficiently reflected in the statistics, as they do not take into consideration the heterogeneous nature of the territory. Cartography focusing on soil uses and land cover, able to incorporate landscape aesthetics in the structure of fragments as well as their size and shape, is required. The availability of precise, objective studies on the wine landscape has recently emerged as an interesting topic, as wine tourism has become a new socioeconomic niche for wine territories.

Factors in peak flows generation in an experimental catchment of the Central Pyrenees, Spain

Se han estudiado los factores que explican la variabilidad temporal de los picos de crecida en una cuenca experimental del Pirineo Central. Esta cuenca (Arnas, Valle de Borau) fue completamente cultivada hasta hace unos 50 anos y se caracteriza por una respuesta hidrologica casi inmediata frente a cualquier intensidad y volumen de precipitacion. Se ha comprobado que la cantidad total de precipitacion durante cada evento apenas explica la intensidad de los picos de crecida, que muestran una variabilidad muy alta. Las relaciones entre precipitacion y caudal mejoran sensiblemente si se separan las crecidas de estacion fria y de estacion calida. La lluvia registrada durante 3 y 7 dias antes de cada crecida tiene un papel relativamente importante en invierno. Durante el verano y principio de otono la intensidad de los picos de crecida no se relaciona con ninguna variable pluviometrica debido a la fuerte evapotranspiracion y a la separacion existente entre eventos lluviosos