Wind erosion in a marginal Mediterranean dryland area: a case study from the Khanasser Valley, Syria

Abstract

Evidence of wind erosion is widespread in the drylands of the Mediterranean region. The purpose of this study was to quantify the extent of windblown dust and to assess the factors that affect the susceptibility to wind erosion in areas that are marginal due to their aridity. The study was carried out in Khanasser Valley, a typical degraded, marginal area in northwestern Syria. The average annual rainfall is about 200 mm and falls mainly in the winter months. In the valley floor, cultivation of rainfed barley using conventional tillage has spread over the past decades due to mechanization, reducing the area of natural grazing land. After harvest, the stubble is grazed by sheep leaving the land bare and vulnerable to wind erosion during the following hot and dry summer months. BSNE (Big Spring Number Eight) samplers were installed to sample the horizontal flux of airborne dust during the summer months of 1998-2001 at two land uses in the study area, i.e. on natural grazing land and on harvested and grazed barley fields. Sediment samples were collected at weekly intervals. The average daily mass flux of airborne material for the 5 to 100 cm height was 0·285 g cm −1 width for the cropland, as compared to 0·089 g cm −1 width for the degraded grazing land. During two of the four seasons, more than 45 per cent of the total airborne sediment trapped for the season was captured during a single week, at both landuse locations. The quantity of airborne materials transported by wind was related to the wind factor, soil management and surface conditions. Nutrient and organic matter content of the airborne sediments exceeded the amounts in the parent soils, indicating that wind erosion could contribute to nutrient depletion of the source areas.

Climate Change and Food Security in West Asia and North Africa

“…The amount of SOM depends on the input of biomass C and its rate of decomposition. The SOM concentration is also extremely low because of the centuries of cultivation by extractive practices, and the losses through accelerated erosion by wind (Masri et al 2003 ) and also water . Pedological factors which reduce the rate of mineralization are the amount of clay and the predominant clay minerals, and nature of exchangeable cations ( Oades 1988 ).…”

“…Bessam and Mrabet ( 2003 ) reported that the SOC pool in 0-25 cm layer increased by NT farming at the rate of 1.4 and 0.66 Mg C ha −1 year −1 after 6 and 11 years, respectively. A study conducted in the Khanasser Valley, northwestern Syria, showed that SOM concentration of the airborne sediments exceeded the amount in the parent soil (Masri et al 2003 ). There was some improvement in soil quality of the surface 0-2.5 cm layer (Namr and Mrabet 2004 ).…”

Calibration of RWEQ in a patchy landscape; a first step towards a regional scale wind erosion model

“…At an altitude of 350 m above sea level, the valley is rather flat. Annual rainfall ranges from 150 to 250 mm and the rainy season starts in October and ends in May (Masri et al, 2003). Wind in the dry season (from June to September) travels from south to west with exceptional large wind events from other directions.…”

“…Wind in the dry season (from June to September) travels from south to west with exceptional large wind events from other directions. During the dry season, the daily average wind speed (at 2 m height) is high and may exceed 10 m s À1 (Masri et al, 2003). Monthly average wind speed in the valley varies from 3.5 m s À1 in the south up to 4.4 m s À1 in the north (Bruggeman et al, 2008).…”

“…Calcisols, Gypsisols, Leptisols, and Cambisols are the main soil types in the valley (Masri et al, 2003). These soils are well-drained and have clay-loam to sandy-loam texture.…”