This table reports vascular plant species composition and percent cover recorded in 25 m² vegetation plots at each of 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. Data were collected in the field during the snow-free season through visual estimation of ground cover in square plots delimited with measuring tapes and stakes. All vascular plant species present in the plot were listed and the cover of each species was estimated following a modified Braun-Blanquet scale expressed as percent cover classes (<1, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80%); empty cells indicate species absence at the sampling point. The table includes 388 plant taxa identified to species level (with a few aggregates and subspecies where morphological discrimination in the field was not possible); nomenclature follows Pignatti et al. (2017-2019), Flora d'Italia, 2nd edition. 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 (landform type: CS, DG, F1, F2, RGa, RGr, SF, SS) and Code Area (site code; 29 sites). Cover estimates for vegetation layers, rock outcrops, debris and mosses were also recorded in the field but are not included in this species- level table. The vegetation data for the Breuil site (Bgl, Brg) were provided by Elisa Giaccone. Species identification was supported by reference floras.

Vascular plant species cover data per 25 m² plot, 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 (388 species) as cover class values,: <1 (less than 1%), 1, 5, 10, 15, 20, ..., 80 [%]; empty cells indicate species absence at that sampling point.