Effect of amendment C:N ratio on plant richness, cover and metal content for acidic Pb and Zn mine tailings in Leadville, Colorado

Biosolids and woody debris were applied with target C:N ratios of 8:1 to 50:1 to phytotoxic, acidic, high metal mine tailings to test the effect of amendment C:N ratio on native plant restoration. Total soil C decreased over time indicating an active microbial community. The 8:1 treatment initially had no growth, the highest plant cover for the final sampling (86.8 ± 13.8%) and the lowest number of species (3.33 ± 0.4). The greatest number of species was in the 30:1 treatment (5.44 ± 0.45). Plant cover increased over time for all treatments from 44.7% in 2001 to 71% in 2005. This response was consistent across all except for the 30:1 treatment, which showed a slight decrease in the final year (65 ± 11%). Volunteer species and evidence of animal grazing were observed in all amended plots. Results indicate that a C:N ratio ≥ 20:1 increased species diversity.