Wind erosion in the central Ebro Basin under changing land use management. Field experiments with a portable wind tunnel W. Fister * , J.B. Ries Department of Physical Geography, Trier University, Behringstr., 54286 Trier, Germany article info Article history: Received 25 March 2007 Received in revised form 1 May 2009 Accepted 19 May 2009 Available online 21 June 2009 Keywords: Animal trampling Extensification Physical soil crusts Tillage simulation Wind tunnel abstract The agricultural landscape in the semi-arid central Ebro Basin is changing from dry farming towards land abandonment. This study aims to describe quantitatively the influence of this land use change onto wind erosion susceptibility in this region. Additionally, the effects of tillage operations on wind erosion rates were evaluated. A portable wind tunnel was used to assess the relative sediment loss rates at three test sites near Zaragoza. Three different land use systems varying in crust disturbance level were investigated – (1) fallow land with undisturbed physical soil crusts, (2) simulated sheep trampling and (3) conven- tional tillage (dry farming). The results show that simulations on undisturbed crusted soils produce little soil loss. Consequently, wind erosion can be considered as negligible on these surfaces. Simulated sheep trampling during wind tunnel test runs produce 10 times higher sediment losses than simulations on undisturbed crusted soils. Highest sediment losses (50 times) were observed from rolled surfaces. Because of the ongoing exten- sification process, the distributions of physical soil crusts will most probably further increase. According to the results, this would lead to a reduction of wind erosion susceptibility in the central Ebro Basin depending on intensity and time of sheep pasturing and tillage. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Since the early 1990s, an increasing area of the central Ebro Basin has been abandoned from agricultural use. For instance, during the period from 1990 to 2003 the arable land of the province of Arago ´ n has been reduced by 146.000 ha (w9%) to a level of about 1.5 Mio. ha (Eurostat, 2006). Major reason for this change from arable to fallow or abandoned land is the low profitability in this semi-arid region. Although since 1992 large set-aside programs, which are subsidised by the European Union, play an important role as well. Following this land use change the relative importance between wind and water erosion is changing and farmers have to adapt their agricultural operations. For example, if arable land is abandoned, physical soil crusts develop more frequently. During rainstorms, crusted fields may cause higher surface runoff and therefore higher sediment losses due to water erosion than prior abandonment (Rice et al., 1996; Ries and Hirt, 2008). Usual miti- gation measures by farmers would be tillage operations to reduce crusting, but this would increase the intensity of wind erosion. In their ‘‘Soil erosion map of Western Europe’’, De Ploey et al. (1989) consider the central Ebro Basin as susceptible to wind erosion. However, as Lo ´ pez et al. (1998) emphasise, no actual data exist about wind erosion in this region. In contrast to wind erosion the amount of water erosion in the central Ebro Basin has been examined quite extensively (Lasanta et al., 1994, 2000; Navas, 1990; Ries, 2002; Ries and Langer, 2002; Seeger, 2007). With their research, Lo ´ pez et al. (1998) started to fill this gap in knowledge. The subsequent WEL- SONS-project (Wind Erosion and Loss of Soil Nutrients in semi-arid Spain) focused on the effects of conventional tillage and reduced tillage onto wind erosion (Gomes et al., 2003a) and the improvement of an existing dust emission model (Gomes et al., 2003b). To extend the information about wind erosion in the Ebro Basin, a portable wind tunnel was used in 46 test runs to assess the relative sediment loss rates by wind erosion at three test sites near the city of Zaragoza. During two field campaigns in September 2005 and April 2006, three different land use systems varying in crust disturbance level were investigated – (1) fallow land with undisturbed physical soil crusts, (2) simulated sheep trampling and (3) conventional tillage. In contrast to the WEL- SONS-project, this study aimed on solving following research questions: (1) Does the present land use change, with focus on soil crusts and sheep trampling, have a quantitative impact on the wind erosion susceptibility of silty soils in the central Ebro Basin? * Corresponding author. Tel.: þ49 651 201 2998; fax: þ49 651 201 3976. E-mail address: w.fister@gmx.de (W. Fister). Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2009.05.006 Journal of Arid Environments 73 (2009) 996–1004