Biochar and ash amendment effects on mine reclamation in the boreal forest

Natural re-vegetation of gold mine tailings, the main waste products of ore processing for gold extraction consisting of crushed rock, is difficult due to their high bioavailability of heavy metals, low nutrient status and limited organic carbon 1-3. Charcoal produced from the burning of organic matter through controlled pyrolysis, hereafter referred to as ‘biochar’, has been utilized extensively in agriculture as a climate-friendly option to remediate nutrient-poor and contaminated soils 4,5. Biochar produced from wood is highly recalcitrant, has a large surface area due to its porous structure and can bind nutrients and water, improving soil fertility 5-7. Biochar can also bind undesirable compounds within the soil such as heavy metals, limiting their bioavailability to plants. Please click on the file below for full content of the abstract

Biochar and high-carbon wood ash effects on soil and vegetation in a boreal clearcut

Additions of fire residues in the form of charcoal and wood ash may better emulate natural disturbance processes in managed boreal forests. We examined the effects of a poplar wood biochar and a high-carbon wood ash on soil and vegetation in a 3-year experiment in NW Ontario, Canada. Both soil amendments increased soil pH and soil Ca levels; high-carbon wood ash also increased soil Cu, Zn, B, S, and Pb. Amendments had large effects on plant community composition, favoring a subset of ruderal species including raspberry (Rubus ideaus) and goldenrod (Solidago canadensis). Addition of high-carbon wood ash resulted in declines in growth of planted white spruce (Picea glauca); a path analysis suggests this was due to effects of toxic elements rather than indirect effects of competition. We conclude that high-carbon wood ash, while qualifying as a type of biochar and having some beneficial effects on soil properties, can enhance toxic metals in boreal forest soils, with negative consequences to early tree growth. Differences in plant species responses to biochars, and potential for toxicity effects and indirect effects mediated by plant competition, will require screening and field trials of potential biochars prior to their use in operational forestry and forest restoration.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author