The Impact of Biosolids and Locally Sourced Microbe Amendments on Root Biomass and the Bacterial Community Associated with Douglas Fir Seedlings Grown In Mine Tailings

Despite progress mitigating the environmental effects of heavy metal mining operations in the US, active and abandoned mine sites and legacy impacts still contribute to the contamination of surface and groundwater. Mitigation through phytostabilization provides one solution by preventing the off-site movement of contaminated mine wastes. In some mine soils, phytostabilization requires modification of acidic, heavy-metal laden soils with low nutrient availability and a microbial community that amplifies acidification. Soil pH can be modified through liming and the application of biochar. Biochars can also sequester heavy metals, but neither biochar nor lime provide nutrients or inocula for altering the microbial community. Locally Sourced Microbes (LSM) adapted to the mine locality and biosolids are potential additives for enhancing and sustaining plant growth. In this greenhouse study, we used LSM bioaugmentation and addition of increasing amounts of biosolids (0.25, 0.5, and 2.0%) to biochar/lime-amended mine soil to determine if these additional amendments impacted plant growth and rhizosphere microbial composition of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco].