This table provides activity density data for adult spiders (Arachnida: Araneae) collected by pitfall trapping at the 768 sampling points of the HIGH-PBS dataset, distributed across 29 high-elevation sites in the Italian Alps and Apennines (1,875–3,120 m a.s.l.) and surveyed between 2010 and 2023. Sampling was carried out with one pitfall trap (plastic vessel, 7 cm diameter, 10 cm height) placed in the centre of each 25 m² vegetation plot, baited with a wine-vinegar and salt mixture. Traps were active throughout the snow-free season (typically early July to late September) and were emptied and refilled approximately every 20 days. For each species column, the value reported is the activity density, computed as the number of adult individuals captured divided by the number of trap-days, averaged across the trapping period; empty cells indicate species absence at that sampling point. Values for sites sampled over consecutive years are aggregated across the full sampling period. The table covers 128 Araneae species identified to species level; identification followed Nentwig et al. (Spiders of Europe, araneae.nmbe.ch) and nomenclature follows the World Spider Catalog. Species identification was additionally supported by expert taxonomists (Marco Isaia, University of Turin, Italy; Francesco Ballarin, Tokyo Metropolitan University, Japan). Voucher specimens are preserved in ca. 70% ethanol at the MUSE - Science Museum of Trento (Italy) and at the Museo Civico di Scienze Naturali "E. Caffi" of Bergamo (Italy). Each row is identified by three columns: Event label (unique sampling point identifier, primary key shared with the other five tables of the dataset), Code Landform (CS, DG, F1, F2, RGa, RGr, SF, SS) and Code Area (29 site codes).

Spider (Araneae) activity density data per pitfall trap, containing: Event label: sampling point identifier (Code: Multiple naming conventions are used, reflecting different sampling campaigns: format 1 (395 points): Site.Landform.Plot.Point (e.g., Agl.CS.1.a); format 2 (275 points): SITE##X (e.g., AGO32B, CLA31A, PEI12A); format 3 (30 points): SITE##.X (e.g., LAZ01.A); format 4 (24 points): U##.X (e.g., U05.A) — Val d'Ultimo site; format 5 (other): site-specific codes (e.g., FRA-FRO11A, SORC3.1A); two labels end in .vista (visual surveys on previously sampled plots), Latitude, longitude, elevation, location of sampling event, * Code Area: site code, * Code Landform: landform type, * Year of sampling, * Species columns (128 species): activity density values [individuals/trap/day]: values represent the number of individuals captured per trap per day, averaged across the trapping period; empty cells indicate species absence at that sampling point.