An Exceptional Rainfall Event in the Central Western Pyrenees: Spatial Patterns in Discharge and Impact

An exceptional rainfall and hydrological event occurred on 19–21 October 2012 in the central western Pyrenees and was particularly significant in the Upper Aragón River basin and its tributaries, mainly the Irati River. Analysis of historical records showed that, considered separately, the event of 19 and 20 October ranked between the second and fifth highest most extreme daily precipitation events. For the two days combined (with a total between 200 and 260 mm), the precipitation event was the most extreme 2‐day event among all observation stations but one. The consequent flood destroyed part of an urban area, and a long stretch of a national road triggered landslides, enlarged the alluvial plain and caused generalised soil erosion in cultivated fields cropped with winter cereals. Badlands in the marls of the Inner Depression yielded high volumes of sediment. The floods in the tributaries were relatively moderate (return periods of 14–42 years), whereas in the Upper Aragón River, the flood corresponded to a return period of approximately 400–500 years and to 142 years at the end of the Yesa reservoir, although difficulties in estimating the discharge increased the uncertainty of these values. The Yesa and Itoiz reservoirs considerably reduced the intensity of the flood in the middle and lower Aragón River and confirmed the importance of the water level in the reservoirs when such rainfall events occur. The water storage in the Yesa reservoir increased from 16% to 53% as a consequence of the event. More integrated studies are necessary to decrease the risks associated with flood hazards. This is particularly the case in mountain areas, where the steep slopes and longitudinal gradients of the rivers shorten the concentration time of floods and increase the energy that erodes channels and riverbanks. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of selenite additions on microbial activity and dynamics in three soils incubated under aerobic conditions

Three soils were incubated for 4-day periods with selenite (0-5 mg Se kg⁻¹) and the effect of straw amendment was also studied for one of these soils. The same soil was also incubated for up to 6 weeks, with and without straw and selenite (0-2 mg Se kg⁻¹). Changes in microbial activity (oxygen respiration) and dynamics (total, fungal biomass; bacterial density number) were assessed. Selenium fractionation and volatilization were also quantified. Selenium addition had no marked effect on respiratory activity, total and fungal biomass whatever the incubation period, but inhibited the growth of heterotrophic bacteria in the longer term. When straw was added, the same trend was observed with more variability. The volatilization losses of Se differed between soils but did not vary significantly over the 6-week period and were not affected by straw addition. Freshly added Se was more easily extracted than native soil Se and its extractability decreased with time, whereas no change in the fractionation of native Se was observed. This study shows that moderate additions of Se may influence microbial dynamics in aerated soil but could not establish a causal link with changes in Se fractionation.     

Gene pool and connectivity patterns of Pinna nobilis in the Balearic Islands (Spain,Western Mediterranean Sea): Implications for its conservation through restocking

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Evidence of differential spreading events of grapevine pinot Gris virus in Italy using datamining as a tool

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Particulate organic matter as a source of variation in denitrification in clods of soil

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