Abstract
Abstract. This study presents the preliminary results of the local energy budget and dynamic characteristics of the surface atmospheric boundary-layer (SBL) during the WELSONS (wind erosion and losses of soil nutrients in semiarid Spain) experiment. Some Mediterranean regions suffer land degradation by wind erosion as a consequence of their particular soil and climate conditions and inappropriate agricultural practice. In Spain, where land degradation by water erosion is well known, the lack of field studies to quantify soils losses by wind erosion resulted in the European Community organizing a scientific program for this specific issue. The European programme known as WELSONS was devoted to study the wind erosion process in central Aragon (NE Spain). This multidisciplinary experiment, which began in 1996 and finished in 1998, was carried out over an agricultural soil which was left fallow. Within the experimental field, two plots were delimited where two tillage treatments were applied, a mould-board ploughing (or conventional tillage denoted CT) and chisel ploughing (reduced tillage denoted RT). This was to study on bare soil the influence of tillage method on surface conditions, saltation flux, vertical dust flux, erosion rates, dynamics characteristics such as friction velocity, roughness length, etc., and energy budget. The partitioning of the available energy, resulting from the dynamics of the SBL, are quite different over the two plots because of their own peculiar soil and surface properties. The first results show that the RT treatment seems to provide a wind erosion protection. Because of the long data recording time and particular phenomena (formation of a crust at the soil surface, very dry conditions, high wind speed for instance), these microclimatological data acquired during the WELSONS programmes may be helpful to test atmospheric boundary-layer models coupled with soil models.Key words: Hydrology (desertification) - Meterology and atmospheric dynamics (general)
Highlights
Soil erosion is a major environmental and agricultural issue that has worsened during recent decades
An analysis of the friction velocity and roughness length shows that the RT is able to reduce wind erosion by an increase of soil aggregation, roughness length and threshold friction velocity
As a ®rst conclusion, the wind erosion process in this region is not a continuous phenomenon: the threshold friction velocity will be often exceeded because of gusty winds blowing over this region, but this is only during very short periods
Summary
Soil erosion is a major environmental and agricultural issue that has worsened during recent decades. The main objective of the WELSONS project is to provide a better understanding of the impacts of climate and land-use changes on soil degradation by wind erosion for agricultural soils in semiarid region of the northern Spain. This can be done over a short-term or a long-term period, ®rst, by investigating the removal of nutrient-rich soil particles due to wind erosion, and by developing a soil nutrient emission model expressed in terms of parameters which are likely to be modi®ed by those changes.
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