Community of Diptera dwelling in oak canopies in France

Diptera are among the most diverse and ecologically important insect orders in forest ecosystems and hold strong potential as bioindicators of ecosystem transformations under anthropogenic and environmental pressures. We examined the effects of oak decline, a process that alters canopy structure and resource availability, on canopy-dwelling Diptera across 30 oak stands in six French forests. Using green multi-funnel traps placed in the lower canopy, more than 27,000 specimens were collected, representing 60 families and approximately 500 taxa. The dataset contains three tables: (i) Taxonomic data: the list and abundance of the taxa collected for each forest, stand (stand #), trap (trap #), and survey date (date1, date2, survey #). (ii) Stand and plot characteristics: environmental and structural variables describing the 30 stands and 60 plots where the study was conducted, including location (forest, stand #, trap #, coordinates), decline severity indices (DSI) estimated across three spatial buffers (DSI 25 m, DSI 200 m, DSI 500 m), mean stand height, mean oak density, mean oak diameter at breast height (DBH), tree density, and oak basal area. (iii) Ecological traits of sampled taxa: functional attributes including associations with flowers (floricolous), forests (silvicolous), decaying or dead wood (saproxylic), tree cavities (cavicolous), sap runs, soft fungi (mycetobiont), and soil or litter. This dataset is associated with a manuscript currently submitted to Insect Conservation and Diversity. Further details on materials and methods are provided in the manuscript.