Further observations on the phenology and spatial distribution of arthropods in the canopy and understory of a Mediterranean mixed stand (Collserola, Catalonia), with emphasis on Diptera and Hymenoptera

This work is part of permanent monitoring that has been conducted since 2009 in the Serra de Collserola Natural Park, and focuses on the activities of families of Diptera and Hymenoptera sampled in a Mediterranean mixed forest of Pinus-Quercus. From April to October of 2012, samples were taken in the canopy and understory, with a total of 7789 specimens with Diptera (1393; 17.9 %) and Hymenoptera (1039; 13.3 %) among the dominant groups. We found a clear stratification of arthropods, where the canopy showed not only as the layer where the bulk of the activity takes place, but also as the most biodiverse stratum. These results contrast with previous studies in the same area where the understory played a dominant role compared to the canopy. The differences between the results of the first study and those obtained in this study show the need to focus attention on the various factors that influence the activity of arthropods between strata with full and partial sun exposure.