PS 42-37 - Effects of simulated grazing on fire-treated mine tailings for restoration

Background/Question/Methods

Land areas impacted by mining must be reclaimed to required standards that are in line with proposed end land uses for the area. Historically reclamation goals focused on obtaining a green vegetative cover using agronomic grass species to address erosion and other issues. However, reclamation goals have transitioned to rebuilding more functional ecosystems of native grass and forb species with a focus on diversity. Sites previously reclaimed with agronomic grasses are often persistent monocultures that, limit diversity and the opportunity for native species to become established. Prescribed burning may help by providing initial disturbance. This study was done to determine if further disturbance in the form of mechanical clipping, acting as simulated cattle grazing, post burn could further aid transition in vegetative regime. In the fall of 2020, eighteen turves collected from Highland Valley Copper mine, British Columbia, Canada were burned and then seeded with selected native forbs and grasses. Clipping was performed in moderate and heavy treatments after one and two months to a stubble height of 3.75 cm and 7.5 cm, respectively, while a control where no clipping occurred was set to test the efficacy of burning and seeding resulting in six replicates per treatment.



Results/Conclusions

At the end of three months, cover was determined, turves were harvested, and cumulative biomass production was determined for agronomic grasses, native grasses, and all forbs. Data was analyzed using one-way ANOVAs. Burning followed by moderate levels of clipping resulted in the lowest agronomic grass biomass and cover while showing a significant increase in forb biomass and cover. Although changes to native grass biomass were not significant, a trend appeared with moderate clipping showing the highest biomass and a significantly higher cover of native grasses than the heavy treatment, but not the control. Disturbance in the form of fire followed by grazing could open the stand, reducing agronomic cover, allowing these sites to transition to more natural states.