UAV, airborne, and terrestrial LiDAR data; RGB imagery; and reference ground-based measurements at the tree level (location, tree species, height, crown dimensions, diameter at breast height, crown height, etc.) were collected in the Krkonoše Mts., Czechia, with the aim of creating a multimodal dataset of sample plots covering the unique gradient of canopy closure. Plot level data from three different parts of the treeline ecotone (upper forest limit, intermediate part of treeline ecotone, upper tree limit, tree height) is present along with individual tree locations and point clouds, LiDAR-derived crown projection areas, crown diameters, and bounding boxes. Supplementary material includes tree descriptions and marked imagery.