Responses in germination and early seedling growth of Vachellia caven and Baccharis linearis cultured in substrates designed for the rehabilitation of mining tailings deposits

Mining tailings are generally infertile, structurally poor and biologically inactive, limiting plant establishment. This study assessed the use of tailings, sewage sludge, and irrigation dam sediment as substrates for germination and early growth of Vachellia caven and Baccharis linearis , two native Chilean species with potential for phytostabilisation. Greenhouse trials included five treatments combining sediment (S) and sludge (SL) in ratios from 100:0 to 0:100, plus an additional treatment with 5% tailings. V. caven reached its highest germination (80%) and survival (66%) in 100% sediment, while the 50% S – 50% SL treatment produced the lowest performance (22% and 12%, respectively). Sludge-rich mixtures increased biomass but reduced aeration and drainage, generating slender seedlings (SI > 10). B. linearis performed best in 100% sediment (8.4% germination, 6.1% survival) and showed very low establishment in sludge-only substrates. Its sensitivity to organic and saline loads limited its potential in high-sludge media. Adding 5% tailings did not significantly affect germination or growth in either species. Results indicate contrasting species-specific responses: V. caven showed greater tolerance to sludge and tailings, maintaining growth in mixed substrates, whereas B. linearis was restricted to sediment-dominated media. These findings highlight the importance of substrate composition for effective phytostabilisation strategies.