Nadir quadrat photographs for grid-point intercept assessment of ground vegetation cover from transects around forest plantations in South and West Iceland (2025)

This dataset contains 1,926 nadir (overhead) photographs of ground vegetation cover collected at 16 forest plantation sites in South and West Iceland between 11 May and 3 September 2025. The photographs were taken as part of a broader field survey of self-seeding of lodgepole pine (Pinus contorta Douglas ex Loudon) in habitats surrounding forest plantations in Iceland. Sampling design. Up to four transects (≥100 m long) were established at each site, radiating outward from the plantation edge. Transect 1 followed the prevailing wind direction, while transects 2–4 were placed at 90° intervals. A 0.5 × 0.5 m quadrat frame subdivided into 25 cells (10 × 10 cm each) was placed at 10 m intervals along each transect and photographed vertically from approximately 1.7 m above ground. GPS coordinates were recorded for each quadrat. Vegetation cover was not estimated in the field; the photographs were collected for subsequent office-based assessment using grid-point intercept (GPI) analysis. Dataset contents. The dataset comprises: 1,926 JPEG photographs organized by site in the photos/ folder; quadrat_metadata.csv, containing per-quadrat GPS coordinates, elevation, distance from the plantation edge, distance to the nearest coastline, and date and time of photography; ( sites.csv, containing descriptions of the 16 plantation sites, including location, region, area, year of establishment, and elevation; transects.csv, containing azimuth, start and end coordinates, measured length, and quadrat count for all 61 transects; and README.md, containing full documentation. Coverage. The 16 sites span an elevation range of 3–215 m a.s.l. and include a variety of Icelandic habitat types, such as heathlands, grasslands, wetlands, lava fields, and moss carpets. Photographs are named according to the convention SITE_TRANSECT_grDISTANCE.jpg, where DISTANCE indicates metres from the plantation edge (e.g. YBF_3_gr320.jpg = site Ytra-Bæjarfjall, transect 3, 320 m from the plantation edge). All coordinates are provided in WGS84 (EPSG:4326).example.png. Representative nadir quadrat photographs from the dataset: bare lava field with sparse vegetation (SSH_3_gr410.jpg) lichen heath with a lodgepole pine seedling (SSH_2_gr030.jpg) grass-dominated sward (SRR_1_gr030.jpg)