Biofuel harvests from forests involve large removals of available nutrients, necessitating accurate measurements of soil nutrient stocks. We found that dilute hydrochloric acid extractions from soils released far more Ca, Na, and K than classical salt–extracted exchangeable nutrient pools. The size of these acid–extractable pools may indicate that forest ecosystems could sustain greater biomass extractions of Ca, Mg, and K than are predicted from salt–extracted exchangeable base cation pools.