| Summary: | Iceland is nowadays the European country with more active soil erosion. Combined with harsh climatic conditions and frequent volcanic activity, sheep grazing has been pinpointed as one of the main reasons for the high degree of vegetation and soil degradation in Iceland. Beyond the direct damage to vegetation through feeding and trampling, sheep grazing can also influence vegetation recovery affecting the production and dispersion of seeds, or the occurrence of bare ground providing substrate for aeolian deposition. The goal of this study was to analyze the impact of sheep grazing on seed rain and aeolian deposition in summer rangelands of Iceland. We studied three sites (Auðkúluheiði, Skeiðarársandur and Þeistareykir), with different susceptibility to soil erosion. Within each site we placed 10-12 plots on each of 2 habitats with contrasting vegetation cover. Sheep grazing was excluded from half of the plots. We installed 3 seed traps in each plot, during 4 weeks in summer 2016 to collect seeds (counted by germination) and aeolian deposits. We found no effect of sheep exclusion neither on seed rain nor in aeolian deposition, but in general more seeds and less sand were recovered from the fenced plots. Seed rain and aeolian deposition were significantly greater in habitats with less vegetation cover. In Skeiðarársandur, rates of aeolian deposition were significantly greater. Further studies analyzing the number of seeds per specie and during longer periods are needed to characterize the habitats and sites and the effect of grazing on seed dispersal and aeolian deposition.
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