Plant dominance along an experimental nutrient gradient.

Fertilization experiments in an 8-yr-old field demonstrated that N was the major limiting nutrient of N, P, K, Ca, and Mg, and suggested that Mg became limiting when N was added. After fertilization experiments, this field was disturbed via disking and divided into 36 plots for a Latin square design experiment on the effect of N:Mg fertilization ratios on vegetation patterns. By the 2nd year, the major species had separated along the imposed N:Mg gradient, with Agrostis scabra dominant at the low Mg but high N end, followed by Agropyron repens, Berteroa incana, Oenothera biennis, and Aristida basiramea which was dominant at the high Mg but low N end of the gradient. An unmanipulated resource, light availability at the soil surface, was significantly affected by the treatments. Spatial heterogeneity in the relative availability of soil nutrients thus may be one cause of spatial heterogeneity in early successional vegetation. -from Author