Soil-Dwelling Insect Diversity Along a Post-Mining Recovery Gradient: Associations with Soil Chemical Properties and Mercury Contamination

Gold mining removes vegetation and topsoil, often leaving mercury (Hg) in the soil. However, the recovery of soil insects on mined land is poorly documented because soil macrofauna are usually analyzed as a single group. This study examined soil-dwelling insects along a time-since-mining gradient in an artisanal gold mining landscape in Dharmasraya Regency, West Sumatra, Indonesia, and related them to soil chemical properties. Four land-use conditions on Ultisols were compared from January to March 2026: active mining, 5-year and 10-year ex-mining land, and secondary forest. Insects were hand-sorted from three 30 cm × 30 cm × 20 cm monoliths per condition and identified to family level, and soil pH, organic carbon, total nitrogen, C/N ratio, and Hg were analyzed. In total, 51 insects from 11 families and five orders were found, none of them on active mining land. The number of families rose from 4 to 8 and 11, and the Shannon-Wiener index from 1.27 to 1.81 and 2.24, at 5 years, 10 years, and in the forest. Ants dominated recovering sites, but their share fell from 44.4% to 25.9%. Diversity correlated positively with organic carbon (r = 0.98) and negatively with Hg (r = −0.97), although these exploratory results rest on four land uses. Family-level insect indicators may support monitoring of rehabilitation on gold-mined land.