Ponderosa pine seedling density through time by height class: (a) first entry fire seedlings 0.01 m to 0.15 m tall, (b) second entry fire seedlings 0.01 m to 0.15 m tall, (c) first entry seedlings from 0.16 m to 1.0 m tall, and (d) second entry seedlings from 0.16 m to 1.0 m tall. Note the difference in y-axis scale between (a) and the others. Bars and lines represent means and SE. Time of plot measurement indicates when measurements occurred: Pre burn = immediately pre fire, numbers indicate years post fire. No significant differences were found. Data from permanent monitoring plots located at Zion National Park, Utah, USA.