Harsh conditions hinder the establishment of trees in restoration of forests. Management options to increase survival such as watering or shading may be costly or infeasible. However, low-cost techniques like soil amendment with biochar (which enhances growth environment) and soil transfers (which introduces beneficial microbes) may increase establishment success. To assess the potential effects of biochar and forest soil transfers on woody plants performance we followed a two-pronged approach. We conducted a meta-analysis on the use of biochar on woody plants in various restoration contexts. We also carried out a field experiment where tree seedlings of Quercus rubra were transplanted in three restoration settings. Seedlings were planted under four treatments: soil inoculation and biochar (SB), only biochar (BC), only soil inoculation (SI), and control (C). We then monitored seedlings growth and survival.

Results from the meta-analysis suggest positive effects of biochar on woody plant biomass, with an overall effect size of 0.03 ± 0.03 (mean ± SD) overall. However, effects varied widely among the genera analyzed and were negative for Quercus (-0.04 ± 0.002). In our field experiment, although we did not find significant differences among treatments, highest survival probability resulted under SI (mean ± SD, 0.11 ± 0.03) and lowest under C (0.04 ± 0.02). There was no effect of treatment on seedling biomass. Results from our two analyses indicate that the use of either, or both, soil amendment techniques may not be effective in all systems, therefore, these should be tailored to suit the focal species and ecosystem.