Soil Organic Carbon and Total Nitrogen data of the heap

The study was conducted in southern Poland at the Sośnica hard coal post-mine spoil heap (50⁰ 16' 22" N, 18⁰ 44' 43" E) in Gliwice and Zabrze, Upper Silesian Coal Basin. Samples from the organic (Oi+Oe) and uppermost mineral horizons (0–10 cm depth, A horizon) were collected from each plot in October 2021. A composite soil sample for each plot was collected from five subsamples (4 points at the corners and one in the middle of each plot).