Fig. 1. Nitrate concentrations during a 21-d aerobic incubation of fire excluded soil with and without 1% charcoal (w/w). Soils were moistened with a nutrient solution containing (NH₄)₂SO₄ and KH₂PO₄ and replicated samples removed at 0, 3, 7, 14, and 21 d and analyzed for extractable NO₃^––N. Error bars represent ± one standard error of the mean (n = 5).