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Forest loss can affect ecosystem processes such as litter decomposition. In semi-arid areas, where forest loss is increasing, soil fauna can play a particularly important role on litter decomposition. However, few studies have addressed the effect of soil fauna on litter decomposition in fragmented semi-arid forests, and none within the dry season in which most litter is shed. In this study, we employed litterbags filled with a common substrate to assess forest size and invertebrate detritivore effects on decomposition. Our results showed an average 14% litter mass loss along 3-9 months of incubation in the dry season, with variations being independent of forest size. Although exclusion resulted in slightly lower abundance of invertebrate detritivores, litter decomposition was similar in exclusion and non-exclusion treatments. We found no significant relationships between fragment size and invertebrate abundance or richness, which in turn did not influence decomposition. Temperature or moisture limitations, and even photo degradation, could have masked differences in decomposition rates related to forest size during the dry season in semi-arid Chaco Serrano. Additionally, harsh environmental conditions during the incubation period could constrain the impact of invertebrate detritivores on the decomposition process. The absence of clear links between forest fragmentation, decomposition and soil fauna during the dry season, when conditions might be particularly limiting for this process, and when invertebrates could be expected to play a particularly important role, opens up new questions and highlights the complexity of this fundamental ecosystem process. (C) 2015 Elsevier Ltd. All rights reserved.