Luis Ortigosa

Land-use changes and sustainable development in mountain areas : a case study in the Spanish Pyrenees

Land-use changes affecting Mediterranean mountains represent the intensification of use in valley bottoms, accompanied by land-use conflicts, and a generalized abandonment of the hillslopes, which in the past were perfectly integrated in the system of land management. Farmland abandonment, reforestation, diminution of the livestock pressure and substitution of cereal crops by meadows are the most outstanding features of the recent land-use changes. The question is whether the new spatial organisation is in accordance with a longterm policy of sustainable development in mountain areas. The results obtained confirm that farmland abandonment on steep slopes — and the resulting colonization of old fields by a dense shrub cover — and afforestation contribute to control both soil erosion and surface runoff. As a result some of the most important rivers and alluvial fans have recently stabilized their sedimentary structures.

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.

LAND RECLAMATION BY REFORESTATION IN THE CENTRAL PYRENEES

The outmigration that has taken place in the Central Pyrenees since the 1950s has resulted in a great reduction in the rural population and the abandonment of extensive areas. Reforestation has been undertaken by various authorities to ensure the reclama- tion of this land. This paper discusses the recent history of reforestation, the techniques used, and the environmental factors involved. It concludes with an overview of the results of these policies and the success in creating new forested land.

Morphometry of Glacial Cirques in the Central spanish Pyrenees

A total of 206 glacial cirques have been identified in the high valleys of the Aragón and Gállego rivers, Central Spanish Pyrenees, in order to study the environmental factors explaining their distribution (altitude, aspect, lithology) and diverse morphometric features (area, width, length, L/W relations, etc.). The use of bivariate and multivariate statistical analyses confirms that a part of the morphometric variability of the glacial cirques is explained by the environmental factors considered here, but their influence is relatively limited. Altitude is identified as the most important factor, affecting both the length and the degree of over–deepening of the cirques. The role of lithology is less obvious because of its interaction with altitude.

Changes in runoff and erosion as a consequence of land-use changes in the Central Spanish Pyrenees

Abstract Both in small experimental plots and in the “Aisa Valley Experimental Station” (Central Spanish Pyrenees), the role of different land-uses in explaining runoff and sediment yield is being studied in closed, experimental plots. In these plots, continuous information on overland flow and suspended and solute sediment concentration is obtained. Results suggest that cereal cultivation in steep slopes encourages soil erosion, especially under non-conservative systems. The passage of cereals into meadows represents an improvement of the hydrological functioning, which reaches its most positive values with colonization by a dense shrub cover.

THE STUDY OF THE SPATIAL ORGANIZATION OF GEOMORPHIC PROCESSES IN MOUNTAIN AREAS USING GIS

The distribution of active geomorphic features in an area of the Central Spanish Pyrenees has been studied using GIS techniques and multivariate statistical procedures. First, the geomorphologic map of the area was digitized to include the geoforms of present or very recent geomorphologic activity: mass movements, forms derived from overland flow, and phenomena linked to thermic contrasts or the persistent presence of ice in the soil. Second, a Digital Elevation Model was produced, allowing automatic calculation of the gradient and exposure maps. Finally, a multivariate statistical technique was used to indicate the most important factors in the spatial organization of the geoforms. The very important role played by the lithology was confirmed, since some types of rocks favor the presence of certain geoforms and yet are unfavorable for others. The most significant result is that from discriminant and hierarchical cluster analysis three groups of geoforms can be defined, which show a very similar spatial pattern as a consequence of similar environmental interactions. One of these groups appears to be related to the deforestation that has lowered the upper forest limit since the eleventh century.

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

Sediment sources during the traditional land-use system in the Spanish Pyrenees

Abstract During the traditional land management system intense erosion processes affected the Spanish Pyrenees up to 2200 m a.s.l. The destruction of the upper forest levels and the expansion of the cultivated fields on the sunny, steep slopes greatly increased sediment yield to the river channels. Soil erosion reached its highest values under shifting agriculture, fallow land and, in the shrubland areas, immediately after a wildfire. Both in the subalpine and in the submediterranean areas, deforestation explains not only the main features of the landscape functioning but also the fluvial dynamics.