sample data

Thirty sampling sites were selected for each ecosystem. At each sampling site, a 20 m × 20 m plot was established. Within each plot, three soil profiles were randomly excavated, and soil samples were collected at six depth intervals (0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm) for DNS, DAS, ORF and four depth intervals (0–10, 10–30, 30–50, and 50–100 cm) for OIF (Yu et al., 2026). Soils from the same depth were composited to obtain mixture samples. This compositing strategy was used to represent plot-level mean conditions at each depth, although it may reduce microscale heterogeneity within individual plots. Visible roots, plant residues, and coarse fragments were removed in the field. All samples were air-dried, gently ground, and sieved through a 2 mm mesh prior to laboratory analyses.