An experimental study of the effects of pH and nitrogen on grassland vegetation

The response of plant species to a full-factorial experimental manipulation of soil pH and soil N in a Minnesota old field is compared to patterns observed in a chronosequence of old fields. Agropyron repens reached its greatest abundance in low pH but high N treatments. Schizachyrium scoparium was less affected by N, but was most abundant at low pH. Poa pratensis had its greatest relative abundance in high N and high pH treatments. Total biomass and species richness were also influenced by the treatments. The pH and N responses did not explain the patterns observed in the old field chronosequence unless the differential colonization abilities of the species and the relationships between soil pH, soil N and successional age were considered. -from Authors