a b s t r a c tClimate, lithology, soil and especially, intense land use/cover changes, make SE Spain very vulnerable to runoff generation and water erosion leading to loss of nutrients and organic matter and to infrequent but devastating floods, reservoir siltation and mass failures. This susceptibility has led to heavy economic investment and research efforts since the 1980s, making this region a worldwide reference for understanding the hydrology and geomorphology of semiarid ecosystems. Runoff and soil erosion have been intensively studied throughout the last decades in various natural ecosystems as well as in abandoned farmlands. Research has considered a wide range of methods and spatial and temporal scales. This paper reviews the methods and data describing runoff generation and water erosion, synthesising the key processes involved, rates, thresholds and controlling factors from a scaledependent perspective. It also identifies the major gaps in current knowledge to provide recommendations for further research towards solutions that reduce the negative impacts of erosion. Research in SE Spain has contributed significantly to a better understanding of the effect of spatial and temporal scale on runoff and sediment yield measurements, and highlighted the important role of distinct erosion and sediment transport processes, hydrologic connectivity, spatial and temporal patterns of rainfall, the occurrence of extreme events and the impacts of land use changes. The most effective ways and challenges to predict runoff, soil erosion and sediment yield at the catchment scale are also discussed.

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Amensal indirect interactions between a Klebsiella pneumoniae microcin-producing strain and several Escherichia coli strains, all of intestinal origin, were studied. Mixed batch cultures of both microcin-producing and microcin-sensitive strains showed that microcin production and excretion into the medium allowed the producer strain to prevail over sensitive strains, even when initial competition conditions were highly unfavourable for the producer. Mixed cultures also showed the production of a microcin-antagonist by the same microcin-producing strain when the nutrients in the medium had been depleted. The antagonist apparently promoted the viability of sensitive cells already damaged by microcin. These results have likely ecological implications.

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