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Universidad de Córdoba (2015)

Procesos distribuidos en la generación y transporte de escorrentía y sedimento en olivar a diferentes escalas

Burguet Marimón, María

Titre : Procesos distribuidos en la generación y transporte de escorrentía y sedimento en olivar a diferentes escalas

Auteur : Burguet Marimón, María

Université de soutenance : Universidad de Córdoba

Grade : Doctoral Thesis 2015

Soil erosion and land degradation are two of the major environmental problems in Spain, which especially affect the South and South-East of the country. According to statistics provided by the Spanish Ministry of Agriculture, Food and Environment (MAGRAMA, 2015), 22.63 % of this soil is affected by ‘high’ erosive problems corresponding to arid or semi-arid environments. In most of the cases, the erosion processes are recurring, intermittent, ongoing and irreversible. Soil loss must be seen as a holistic process affecting not only to its biotic activity but also to the role of soil in the carbon regulation and emission to the atmosphere, its food production capacity and in general, its capacity to sustain society. Therefore, it is essential to fully understand soil degradation processes so that solutions which will decrease and ideally eliminate that degradation can be provided. The Mediterranean region is characterized by sparse vegetation and shallow soils, steep topography and large variations in precipitation levels and storms with high erosive power. This makes erosion an endemic characteristic of this region. The main driver of erosion in these conditions is water, which adopts geomorphological forms such as splash, rills or gullies. Olive orchards located in mountainous areas under rainfed conditions in Andalucia (South Spain) have led to soil loss mainly caused by the interactions of their environmental features and unsuitable management practices. A better understanding of the distributed processes in the generation and transport of runoff and sediment at different spatial scales is, however, needed to provide solutions adapted to the farm attributes which minimizing effort and cost. With this in mind, the diagnosis of the main sediment sources and processes taking place on different scales is essential to optimize the temporal and spatial application of different soil conservation techniques, such as for instance those defined by the NRCS (Natural Resources Conservation Service) like conservation tillage, cover crops or the use of buffer strips could be implemented in order to soil preservation. The aims of this work were to characterize and to model the dominant erosion processes that take place in olive orchard watersheds as well as design different soil management strategies to protect the soil. Three different scales of erosion processes have been utilized : [i] one-off measures in which soil water repellency was measured, [ii] hillslope runoff plot were utilized to determine the vegetation sediment trapping efficiency by buffer strips was determined and [iii] watershed in which a sediment delivery distributed model was calibrated in two different olive crop watersheds so the areas prone to erosion could be identified. At the one-off measure scale, soil water repellency (SWR) was characterized from field-based measurements. According to the SWR studies, it is a soil property that might have a significant impact in soil erosion as SWR delays water infiltration, which translates into higher values of runoff and flow concentration and at the same time, higher potential erosion. Thus, in this chapter, the occurrence, persistence and spatio-temporal variation of SWR is evaluated as well as the influence of different tillage systems and soil properties on the appearance of SWR. To achieve that, four different olive orchards with different soil managements (abandoned, herbicide use, conventional tillage and with cover crop) were selected.

Mots clés  : Olivares Erosion Suelos Andalucía Degradación del suelo Degradación Escorrentía Olive orchards Soil Soil degradation Runoff

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