Effects of soil nutrients and fire on seedling establishment of native prairie species

We sought to determine 1) the relationship between seedling establishment rates of target native prairie species and field levels of three soil nutrients (phosphate, nitrate, and ammonium) recorded in fall, winter, and summer, 2) the effect of fire on these three nutrients, and 3) the overall effect of fire on seedling establishment rates of the target native prairie species. Seedling establishment rates were not  significantly correlated with soil nitrate or ammonium. Phosphate was significantly correlated with seedling establishment rates but the direction and strength of the relationship depended on the species, with three species showing positive relationships and three species showing negative relationships. Soil phosphate increased significantly in the burned plots compared to the unburned plots, soil ammonium decreased significantly in the burned plots, and soil nitrate showed no significant differences. These nutrient patterns successfully predicted the overall fire effects on seedling establishment in a separate experiment. The three species with positive correlations between seedling establishment and phosphate had greater seedling establishment rates in the burned plots compared to the unburned plots (two significantly, P≤0.1), and the three species with negative correlations had fewer seeds establish in the burned plots (two significantly (P ≤ 0.1).