Effects of Biochar on Drought Tolerance of Pinus banksiana Seedlings

Drought is a major stressor of tree seedlings regarding both natural and artificial regeneration, especially in excessively drained, sandy outwash soils. While climate change is expected to cause an increase in the total annual precipitation in the Upper Midwest, USA, the timing of the precipitation is predicted to result in longer periods of drought during the growing season. Biochar, a material created through the pyrolysis of organic matter, such as wood waste, has been proposed as a soil amendment that may increase the water holding capacity of a soil. Biochar has mostly been studied in agricultural settings, and less is known about the impact of biochar on forest soils and tree seedlings. We used a greenhouse experiment to test the ability of biochar to improve the drought tolerance of jack pine (Pinus banksiana) seedlings via increased soil water holding capacity. The seedlings were planted in sandy soil treated with three levels of biochar (none, 3% by weight, and 6% by weight) in two experiments, one manipulating the timing of drought onset and the other controlling the amount of water that seedlings received. Our results showed no significant effects of biochar on seedling survival, growth, or physiology under drought conditions. While this outcome did not support the hypothesis that biochar would increase seedling performance, the biochar amendments did not negatively affect seedlings, indicating that biochar may be added to soil for carbon storage without having negative short-term impacts on tree seedlings.